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A/C Question


billys68ss's Avatar
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07-17-03, 03:33 PM   #1  
A/C Question

Hey guys,

As long as I have been here I have never asked for help. That is about to change. I had a car come into the shop today with an A/C condition that I have NEVER seen.
Here are the specifics:
1991 Mazda 626 1.6 4cyl. 5speed manual tranny. R12 sytem.
When the car came in I hooked it up to the machine and it showed low low side pressure. Which would tell me that it is low on freon. I checked and it did in fact have some freon, so the likelyhood of a leak was slim. I tried to add a little freon but it would not take it. This is against my better judgment, but it is the way they want it done where I work even though I have tried to explain that it is not the proper method. Anyway, since I couldnt get it to take any freon, I decided to evac/recharge the system. I did this and put in the proper amount of freon. When I started the car it had 0 low side pressure and around 150 high side. When I turned off the compressor the system equalized just like it should. Every time I turned on the A/C the low side pressure dropped to 0. Considering it equalizes correctly I assume there is no restriction, and the only thing I can think that would make it do this is maybe a valve or switch inside the compressor. Can anyone tell me if I am correct in my thinking as I have NEVER seen this before.
Sorry this is so long winded, but wanted to get all of the details in.
Thanks ahead of time,
Billy

 
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07-17-03, 04:25 PM   #2  
Joe_F
If you want, e-mail me with a fax # and I'll send you an exploded view of the compressor and A/C system from the Mazda parts fiche.

 
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07-17-03, 04:57 PM   #3  
Actually, I have seen this before.. The expantion valve is usually the culprit. It'll allow the compressor to suck the low side "dry", and then the system will equalize back through the compressor to the expantion valve...High pressure bleeding to the low pressure..The compressor doesn't usually block off high side from low side, so the overall system can still equalize..Same could happen if a system had a totally stopped up orifice tube..low low side, high high side, but can still equalize..

 
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07-17-03, 04:58 PM   #4  
Thanks Joe, I dont know the fax number at work, and dont have internet access there either YET! If you could send it in email that would be helpful, if not I understand.
Billy

 
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07-17-03, 05:01 PM   #5  
Msargent.... Thanks alot. That is the info I was looking for. I am still open to other suggestions cause I am really lost on this one. I will let the customer know and maybe save the day with this one.
Thanks again,
Billy

 
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07-17-03, 05:22 PM   #6  
Absolutely!! In a situation like this, any and all ideas are welcome.. I know I can sometimes get into a "mind-set", then another idea from someone else turns on the light..

Good Luck with it!

 
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07-18-03, 05:52 AM   #7  
Joe_F
Billy:

I can send it by fax . I have Mazda on microfiche only, hence I can only print out from the machine and have a hard copy.

Mazda is going to go to parts on CD-ROM, but we have not gotten it yet.

Sounds like MSA has you covered and I would surely agree .

Good job here!

 
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07-18-03, 03:21 PM   #8  
Thanks for the help guys. Turns out I didnt get to test the knowledge offered here. It is a long story, but we didnt fix the womans car. She wanted something for nothing and im the one left holding the bag. She got all of my time for free and her system diagnosed ALL FOR FREE. The only good thing is, she will have to pay someone else to diagnose and repair it if she wants her A/C to work again, cause we didnt tell her what was the problem. SOME PEOPLE!!!
Thanks again for the great responses.
Joe.... Thanks for the offer of the fax. We have Alldata (Somedata) at work, but the diagnostic in there is hokey at best for most cars.
Billy

 
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07-18-03, 04:40 PM   #9  
Joe_F
No problem. Sorry you didn't get the job!

 
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