This is something we hear from time to time, especially when dealing with DIY'ers or with people working on older cars. This usually stems from a lack of understanding of how these systems are energized OR a particular nuance about a specific vehicle.
About a month ago I received a call from a customer to whom I sold a BMW Behr Bosch wing cell (rotary vane) type compressor. The complaint was "My mechanic installed it and it worked fine for about an hour and then it quit."
"OK, what is the compressor doing?"
"Nothing."
"Nothing at all? Does the clutch engage when you energize it?"
"No."
"OK, tell him to disconnect it from the system and jump it direct from the battery."
"He tried that. It doesn't work."
"OK, tell him to test it with an OHM Meter. If the coil is open it is bad. If it reads between 3 and 5 ohms it is good. Also, tell him to check the in line diode and make sure there is continuity through it."
After a day another call came with the news that it still doesn't work.
"OK, send it back and we will check it. If there is a problem we will replace it."
The compressor was returned, and, as I suspected, there was nothing wrong with it. To be on the safe side, we replaced the coil because the potential for erratic or intermittent failure, though rare, is possible and erring on the side of caution is the preferred choice.
A week passed and a second call came in.
"It still doesn't work."
"Then something is wrong with your system or with the way your mechanic is proceeding."
"Would you please speak to my mechanic for me."
"Be happy to. Have him call me."
Louis called me about ten minutes later and assured me the compressor had a good electrical connection with adequate voltage. I in turn assured him the compressor was thoroughly tested and good.
"Well, Louis, when you have power to an otherwise good component and it does not function my first thought is that it is not reaching ground. Are you sure it is grounded?"
"There is only one wire on this coil."
"OK, so the ground is through the body. Does the bracket have bushings on it?"
After a pregnant pause the answer was "Yes."
"Is there a ground strap on the compressor or the bracket."
"No."
"Well that is your problem."
"But, but ...."
"Louis, I am sure that is your problem. Ground the compressor and it will work."
Some older vehicles, most notably Volkswagen's and BMW's, used two piece brackets which incorporated small rubber bushings between the bracket pieces. The bracket bolts passed through the center of these bushings which effectively isolated the bracket and compressor, preventing them from reaching ground. To overcome this a ground strap was used. Obviously, in this instance the ground strap was either missing or damaged.
There are many other reasons, too numerous to mention here, why an otherwise good compressor won't turn on. For more information on this topic please visit our FAQ's at:
http://polarbearinc.com/faqs.cfm
I hope this helps some of you who are working with or restoring older vehicles.
Thanks.
Joe
Friday, October 24, 2008
Wednesday, October 8, 2008
Why Can't I Get This Schrader Valve Out?
A guy came into the store the other day wanting to purchase a new hose or have us fix his old one.
Looking at the hose I asked "What's wrong with it?"
"It leaks right here at the valve" and he pointed towards the hoses R134A high side access port.
"So why don't you change the schrader valve?"
"I can't. It doesn't come out......Never saw such a stupid design......The @@##$#% want you to buy a new hose instead of changing the schrader valve."
I picked up the hose and looked at the high side access port. As I suspected, it had a what is called a primary port adapter......and before you ask, I have no idea why they named it that because there is nothing primary about it and it doesn't work as an adapter for anything. Its' only purpose is that for which it was apparently intended, to make something simple complicated and convoluted. Pi
ctured here is a GM high side Primary Port Adapter. You can identify it by the fact that the schrader valve is non removable. When you look into the opening of the port instead of seeing a pin type depressor with a shoulder that can be turned with a standard schrader valve removal tool, you will see a round plastic ball type depressor that cannot be turned or removed. Also, notice that above the oring there is a lip of sorts. This lip mates almost seamlessly with the female threaded housing in the hose, making it appear to be one piece and non removable. Because of this, and because we are used to dealing with easily removable schrader valves, ones' initial reaction is there is no way to fix the leak and therefore you must replace the hose.....a very pricey error to make.
Replacement and removal of these ports is quite simple. First you must remove all of the freon from the system. Be absolutely certain you have all of the freon out of the system and there is no pressure in it. Failure to do so could cause serious injury or death. The port can violently shoot out of its housing with the force of a bullet releasing freon and oil with it.
Once you are sure there is no pressure in the system, simply use the appropriate sized wrench or socket on the port while holding its' female base (the part in the hose) with a second wrench. This is very important because if the threads bind you will turn the housing instead of the threads and possibly ruin the hose.
Next clean the housing threads, put a little bit of oil on the oring, insert the port into the housing and turn it by hand as far as it will go or until the oring seats. Then snug it up using the two wrenches as described above until the gap above the oring disappears and it once again gives the illusion of being one piece.
Remember, this is an oring seal and does not need to be tightened with super human strength. Once the oing is seated it will seal and hold pressure. The ONLY reason to use a wrench is to tighten it enough that it won't vibrate loose.
That's it. The repair is complete!
I hope this saves some of you a bit of grief should you encounter this.
Until the next time, thanks for reading.
Joe
Looking at the hose I asked "What's wrong with it?"
"It leaks right here at the valve" and he pointed towards the hoses R134A high side access port.
"So why don't you change the schrader valve?"
"I can't. It doesn't come out......Never saw such a stupid design......The @@##$#% want you to buy a new hose instead of changing the schrader valve."
I picked up the hose and looked at the high side access port. As I suspected, it had a what is called a primary port adapter......and before you ask, I have no idea why they named it that because there is nothing primary about it and it doesn't work as an adapter for anything. Its' only purpose is that for which it was apparently intended, to make something simple complicated and convoluted. Pi
ctured here is a GM high side Primary Port Adapter. You can identify it by the fact that the schrader valve is non removable. When you look into the opening of the port instead of seeing a pin type depressor with a shoulder that can be turned with a standard schrader valve removal tool, you will see a round plastic ball type depressor that cannot be turned or removed. Also, notice that above the oring there is a lip of sorts. This lip mates almost seamlessly with the female threaded housing in the hose, making it appear to be one piece and non removable. Because of this, and because we are used to dealing with easily removable schrader valves, ones' initial reaction is there is no way to fix the leak and therefore you must replace the hose.....a very pricey error to make.Replacement and removal of these ports is quite simple. First you must remove all of the freon from the system. Be absolutely certain you have all of the freon out of the system and there is no pressure in it. Failure to do so could cause serious injury or death. The port can violently shoot out of its housing with the force of a bullet releasing freon and oil with it.
Once you are sure there is no pressure in the system, simply use the appropriate sized wrench or socket on the port while holding its' female base (the part in the hose) with a second wrench. This is very important because if the threads bind you will turn the housing instead of the threads and possibly ruin the hose.
Next clean the housing threads, put a little bit of oil on the oring, insert the port into the housing and turn it by hand as far as it will go or until the oring seats. Then snug it up using the two wrenches as described above until the gap above the oring disappears and it once again gives the illusion of being one piece.
Remember, this is an oring seal and does not need to be tightened with super human strength. Once the oing is seated it will seal and hold pressure. The ONLY reason to use a wrench is to tighten it enough that it won't vibrate loose.
That's it. The repair is complete!
I hope this saves some of you a bit of grief should you encounter this.
Until the next time, thanks for reading.
Joe
Monday, October 6, 2008
Pinned By A Volkswagon or Just Because It Looks Like a Duck ...
About 2 months ago I received an inquiry about a Sanden SD7V16 control valve from a customer in Malaysia. After exchanging a few emails the order was placed and the product was shipped.
The Sanden SD7v16 is a variable displacement compressor used by several different manufacturers, most notably certain Volkswagon and Audi models. Here is a very nice article explaining how variable displacement compressors work.
But, I digress ...
About 2 weeks after I shipped the control valve, our part number EX 10067, I received an email from our customer with "Wrong Item!!" in the subject line. The customer then proceeded to explain how we had erroneously shipped him an Ex 1210 which fits an SD7V12 rather than the EX 10067 he needed.
Taking the attitude that since he had it to look at and I didn't and that it was quite possible the product was mis boxed, I simply shipped him a replacement part after I had verified with the manufacturer that I was indeed shipping the correct part and not one that was incorrectly packaged or labeled. Problem solved!
Or so I thought.
Two weeks or so go by and I receive an email with "Wrong Item AGAIN!!!" in the subject line. I think to myself "how could that be?" I verified I shipped the correct part with the manufacturer, so I send a return email questioning the customers reasons and logic.
He replied that if I look at the images I will note that the image depicting EX 10067 has a different "pin" coming out of its end than the image of EX 1210. The part I shipped him resembles the image of EX 1210, not that of the part he wanted, EX 10067.
Note that the valve on the left has a "pin" whose tip is smaller than the overall diameter of the rest of the pin and the valve on the right has a pin with a blunt end.
The customer was correct. What could be going on?
Puzzled, I decided to disassemble an intact compressor to see what was in it and confirm my suspicion that possibly the images were incorrect. No such luck! The images conformed to what my customer was telling me.
Now, both confused and irritated because I had specifically asked a supplier who also happens to be the manufacturer to confirm he sold me the correct valve, and he stated such was the case. I then purchased valves from 3 other suppliers to get to the bottom of this. All of them were the same.
Well, after an ungodly number of emails and phone calls I learned that the type of end on the valves "pin" doesn't matter and for reasons unknown to me or anyone else, the engineers decided it was OK to use the same pin in all valves of this type. My guess is that the pin differences were for ease of identification on the parts shelf because that pin end is non functional, that is, it does not interact with any other component in the compressor. It merely sits in the open space between the valve plate and the rear head, as can be seen in this exploded view diagram of an SD7V16 compressor.
To his credit, my customer accepted my explanation and is going to use the valve. He also promised to report back on the results when the job is complete. I in turn wll note the outcome here, all of which only goes to prove that sometimes, even though it looks like a duck and quacks like a duck it might still be a chicken.
Thanks for listening.
Joe
The Sanden SD7v16 is a variable displacement compressor used by several different manufacturers, most notably certain Volkswagon and Audi models. Here is a very nice article explaining how variable displacement compressors work.
But, I digress ...
About 2 weeks after I shipped the control valve, our part number EX 10067, I received an email from our customer with "Wrong Item!!" in the subject line. The customer then proceeded to explain how we had erroneously shipped him an Ex 1210 which fits an SD7V12 rather than the EX 10067 he needed.
Taking the attitude that since he had it to look at and I didn't and that it was quite possible the product was mis boxed, I simply shipped him a replacement part after I had verified with the manufacturer that I was indeed shipping the correct part and not one that was incorrectly packaged or labeled. Problem solved!
Or so I thought.
Two weeks or so go by and I receive an email with "Wrong Item AGAIN!!!" in the subject line. I think to myself "how could that be?" I verified I shipped the correct part with the manufacturer, so I send a return email questioning the customers reasons and logic.
He replied that if I look at the images I will note that the image depicting EX 10067 has a different "pin" coming out of its end than the image of EX 1210. The part I shipped him resembles the image of EX 1210, not that of the part he wanted, EX 10067.
Note that the valve on the left has a "pin" whose tip is smaller than the overall diameter of the rest of the pin and the valve on the right has a pin with a blunt end.
The customer was correct. What could be going on?
Puzzled, I decided to disassemble an intact compressor to see what was in it and confirm my suspicion that possibly the images were incorrect. No such luck! The images conformed to what my customer was telling me.
Now, both confused and irritated because I had specifically asked a supplier who also happens to be the manufacturer to confirm he sold me the correct valve, and he stated such was the case. I then purchased valves from 3 other suppliers to get to the bottom of this. All of them were the same.
Well, after an ungodly number of emails and phone calls I learned that the type of end on the valves "pin" doesn't matter and for reasons unknown to me or anyone else, the engineers decided it was OK to use the same pin in all valves of this type. My guess is that the pin differences were for ease of identification on the parts shelf because that pin end is non functional, that is, it does not interact with any other component in the compressor. It merely sits in the open space between the valve plate and the rear head, as can be seen in this exploded view diagram of an SD7V16 compressor.
To his credit, my customer accepted my explanation and is going to use the valve. He also promised to report back on the results when the job is complete. I in turn wll note the outcome here, all of which only goes to prove that sometimes, even though it looks like a duck and quacks like a duck it might still be a chicken.
Thanks for listening.
Joe
Thursday, October 2, 2008
Bearing Down on Things
Yesterday my old friend and neighbor Rob came in and purchased a pulley bearing while I was out visiting a client.
Change a pulley bearing on a General Motors compressor ..... piece of cake, right.
Wrong....
Rob took the bearing and gave it to one of his employees instructing him to change it. This is a relatively simple task if you know how to do it.
A few hours later Rob returned with a clutch assembly in hand and said "it worked perfect before. All we did was change the bearing and now it slips.....Can you check it out for me?"
"Sure Rob. Be happy to."
The first thing I did was check the coil with an ohm meter.
"Coils good."
Next I looked at the pulley.
The first thing I noticed was the bearing seal was damaged, obviously from the way they installed it.
"Rob, look at this."
"Whoever did this used the wrong tool. You never put pressure on the face of a bearing seal."
Rob replied, "I know Joe, what did they do?" all the while with a look of disgust on his face.
I said, "Look ....." and I proceded to peer across the face of the pulley and show Rob what had happened.
His employee used the wrong tool to install the bearing and damaged the bearing seal. Then he did not support the pulley properly and proceeded to bend the "face" of the pulley so it was now concave. Of course the perfectly flat "hub" or "drive plate" which mates to this was slipping. It had to because it was only grabbing on the outer edges of the pulley's circumference.
So ....
Here are a few useful do's and don'ts about changing a pulley bearing.
The first rule to remember when installing a new bearing is to never put pressure on the inner race. This stresses the ball bearings and will ultimately cause the bearing to be noisy. When installing a bearing the tool must rest on the outer race so it does not put pressure on the ball bearings or the inner race. Remember, the whole assembly is held together by polished steel balls riding in a polished groove. Damage the balls or the groove and the bearing becomes noisy or, worse yet, it comes apart.
Removing the old bearing is a whole other matter. In most instances, you are forced to put pressure on the inner race to remove it. But that doesn't matter since you are changing it any way.
Above I mentioned that when installing the new bearing the tool must rest on the outer race.
Hmmmm .... this could be a problem for the DIY'er......
Well ..... not really.
Of course, you could get on line and go to your favorite Auto AC parts and supplies dealer, Polar Bear, Inc. and spend a lot of your hard earned dollars with that nice guy Joe over there. This in an of itself is always a good idea ....
but,.... if this is a once a year or once in a life time project, it kind of defeats the purpose of doing it yourself. So, consider ..... what will fit perfectly over the outer race of your new bearing?
How about the outer race of the old bearing?
Simply clean any grease or grit off your old bearing and line it's outer race up with that of the new bearing. Line both bearings up perfectly straight with the bearing housing of the pulley and use a flat piece of metal to press it in.
But .... nothing is as easy as it sounds.
You must be careful to keep everything straight. If the bearing cocks to one side it will jam and cause you problems. It might even damage the bearing or the pulley. All of which brings to mind Rob's original prob
lem ....Notice that the bearing in the pulley pictured below presses out from the rear.
You simply lay the pulley on its face and press the old bearing out of the pulley (or drive it out with a special tool and a hammer). Then wipe it clean and install the new one doing the reverse using your improvised old bearing and scrap metal tool.
Well, .... not exactly. You must be sure to support the bearing housing when you install the bearing. If you support it from the outer edges, as Rob's employee did, you will collapse the face of the pulley, making it concave and rendering it useless.
While we are at it ... A word of caution about presses.
Even the lowly manual arbor press exerts several tons of force when you use it. A hydraulic press exerts much more....* Any* hydraulic press, even the bottle jack style. When you stack objects such as these be aware they can fly out of the machine with deadly force when not perfectly straight. Never stand directly in front of the machine. Always stay to the side and try to use the frame of the press as a "shield".
So, the lesson learned here is that Rob, a seasoned pro, didn't assess the job with respect to the resources he had available. Obviously, his employee was not familiar with changing this type of bearing in this type of part. In terms of time, lost opportunity, damaged parts and wasted labor, Rob would have been better off changing the whole clutch OR, bringing it to someone who has the proper tools and fixtures to do the job.
As a DIY'er, it is critical you think this way since as a general statement, you do not have a complete shop or a network of shops you can bring your mistakes to and get professional help. When in doubt feel free to call us (1800-365-3516). We will tell you what is involved in doing the job and if you need special tools. And, when we don't know, we are not ashamed to say so. But, we will find out for you.
So, till the next time something worth discussing happens, thanks for reading this.
Joe
Change a pulley bearing on a General Motors compressor ..... piece of cake, right.
Wrong....
Rob took the bearing and gave it to one of his employees instructing him to change it. This is a relatively simple task if you know how to do it.
A few hours later Rob returned with a clutch assembly in hand and said "it worked perfect before. All we did was change the bearing and now it slips.....Can you check it out for me?"
"Sure Rob. Be happy to."
The first thing I did was check the coil with an ohm meter.
"Coils good."
Next I looked at the pulley.
The first thing I noticed was the bearing seal was damaged, obviously from the way they installed it.
"Rob, look at this."
"Whoever did this used the wrong tool. You never put pressure on the face of a bearing seal."
Rob replied, "I know Joe, what did they do?" all the while with a look of disgust on his face.
I said, "Look ....." and I proceded to peer across the face of the pulley and show Rob what had happened.
His employee used the wrong tool to install the bearing and damaged the bearing seal. Then he did not support the pulley properly and proceeded to bend the "face" of the pulley so it was now concave. Of course the perfectly flat "hub" or "drive plate" which mates to this was slipping. It had to because it was only grabbing on the outer edges of the pulley's circumference.
So ....
Here are a few useful do's and don'ts about changing a pulley bearing.
The first rule to remember when installing a new bearing is to never put pressure on the inner race. This stresses the ball bearings and will ultimately cause the bearing to be noisy. When installing a bearing the tool must rest on the outer race so it does not put pressure on the ball bearings or the inner race. Remember, the whole assembly is held together by polished steel balls riding in a polished groove. Damage the balls or the groove and the bearing becomes noisy or, worse yet, it comes apart.
Removing the old bearing is a whole other matter. In most instances, you are forced to put pressure on the inner race to remove it. But that doesn't matter since you are changing it any way.
Above I mentioned that when installing the new bearing the tool must rest on the outer race.
Hmmmm .... this could be a problem for the DIY'er......
Well ..... not really.
Of course, you could get on line and go to your favorite Auto AC parts and supplies dealer, Polar Bear, Inc. and spend a lot of your hard earned dollars with that nice guy Joe over there. This in an of itself is always a good idea ....
but,.... if this is a once a year or once in a life time project, it kind of defeats the purpose of doing it yourself. So, consider ..... what will fit perfectly over the outer race of your new bearing?
How about the outer race of the old bearing?
Simply clean any grease or grit off your old bearing and line it's outer race up with that of the new bearing. Line both bearings up perfectly straight with the bearing housing of the pulley and use a flat piece of metal to press it in.
But .... nothing is as easy as it sounds.
You must be careful to keep everything straight. If the bearing cocks to one side it will jam and cause you problems. It might even damage the bearing or the pulley. All of which brings to mind Rob's original prob
lem ....Notice that the bearing in the pulley pictured below presses out from the rear.You simply lay the pulley on its face and press the old bearing out of the pulley (or drive it out with a special tool and a hammer). Then wipe it clean and install the new one doing the reverse using your improvised old bearing and scrap metal tool.
Well, .... not exactly. You must be sure to support the bearing housing when you install the bearing. If you support it from the outer edges, as Rob's employee did, you will collapse the face of the pulley, making it concave and rendering it useless.
Keep in mind also that if you use the old bearing as a tool in order to install the new bearing you will usually have to drive part of the old bearing into the housing. It will probably get stuck. As long as it does not to go too far into the housing you can remove it by holding the pulley and tapping it with a small hammer. If the bearing sits too deeply in the housing you will either have to buy the correct tools or bring it to a properly equipped shop. Another thing to know is that most automotive bearings are secured in place by either a snap (or lock) ring OR they are staked. When working with a snap ring you simply remove and replace it. You need the appropriate snap ring pliers. When working with a bearing that is staked you will need to "re stake" (if there is such a word) the bearing. If there is no snap ring, you will notice a series of "punches", "indentations" or "dimples" on the open side of the bearing housing. These punches slightly collapse the wall of the housing over the outer race of the bearing. When you remove the bearing you expand those "collapses" (another new word) so when you replace it you must stake the bearing again. You do this with a small, very pointy punch and a hammer. Place the punch next to or on one of the original marks on the pulley and give it a sharp rap with the hammer. Do this following the old marks until you get them all and the bearing is now "staked".
While we are at it ... A word of caution about presses.
Even the lowly manual arbor press exerts several tons of force when you use it. A hydraulic press exerts much more....* Any* hydraulic press, even the bottle jack style. When you stack objects such as these be aware they can fly out of the machine with deadly force when not perfectly straight. Never stand directly in front of the machine. Always stay to the side and try to use the frame of the press as a "shield".
So, the lesson learned here is that Rob, a seasoned pro, didn't assess the job with respect to the resources he had available. Obviously, his employee was not familiar with changing this type of bearing in this type of part. In terms of time, lost opportunity, damaged parts and wasted labor, Rob would have been better off changing the whole clutch OR, bringing it to someone who has the proper tools and fixtures to do the job.
As a DIY'er, it is critical you think this way since as a general statement, you do not have a complete shop or a network of shops you can bring your mistakes to and get professional help. When in doubt feel free to call us (1800-365-3516). We will tell you what is involved in doing the job and if you need special tools. And, when we don't know, we are not ashamed to say so. But, we will find out for you.
So, till the next time something worth discussing happens, thanks for reading this.
Joe
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