1979 A/C issue
06-13-2017, 11:27 PM
#1
Advanced
Thread Starter
1979 A/C issue
When I bought my '79, the A/C blew cold air. Now it only blows warm air.
I went to A/C shop today after paying $200 last fall for checkout. Now car still blows warm air. Mechanic said I needed a new compressor. I vaguely understand that today's regs mandate we not use Freon. Said mechanic told me he would take the system back to "original" and fill it from his stash of Freon. He also said that the new refrigerant has "smaller molecules" than Freon and can quickly leak out of older systems which are not as "tight" as modern. He said he saw evidence that the refrigerant he put in last year had leaked out. I'm not that mechanically savvy but if he is going to install a new rebuilt compressor and fill it with Freon with its "bigger molecules ", why not use the old compressor? The number on one of the plates in the car says part number 14006785, is that the CAT number. I can't see under the number clearly on the compressor as it resides under the compressor itself.
My car has the small block and was originally purchased in California.
Questions:
This all seems like gobble-gook to me?
How do I check the existing compressor to see if it is working?
If not working, what part should I be looking for?
Should I convert to new refrigerant and what does that entail?
Should I just replace the compressor and so, with what and use which refrigerant. I'm not asking for a part supplier company name as I understand it's important that we support our contributing suppliers
I'm sorry I ask so many dumb questions. I've learned a lot about owning and buying an older Vette and would be glad to offer my opinions to anyone who asks. I'd like to give back to the Forum to help repay all the great help and advice I've gotten so far. Thank you!
I went to A/C shop today after paying $200 last fall for checkout. Now car still blows warm air. Mechanic said I needed a new compressor. I vaguely understand that today's regs mandate we not use Freon. Said mechanic told me he would take the system back to "original" and fill it from his stash of Freon. He also said that the new refrigerant has "smaller molecules" than Freon and can quickly leak out of older systems which are not as "tight" as modern. He said he saw evidence that the refrigerant he put in last year had leaked out. I'm not that mechanically savvy but if he is going to install a new rebuilt compressor and fill it with Freon with its "bigger molecules ", why not use the old compressor? The number on one of the plates in the car says part number 14006785, is that the CAT number. I can't see under the number clearly on the compressor as it resides under the compressor itself.
My car has the small block and was originally purchased in California.
Questions:
This all seems like gobble-gook to me?
How do I check the existing compressor to see if it is working?
If not working, what part should I be looking for?
Should I convert to new refrigerant and what does that entail?
Should I just replace the compressor and so, with what and use which refrigerant. I'm not asking for a part supplier company name as I understand it's important that we support our contributing suppliers
I'm sorry I ask so many dumb questions. I've learned a lot about owning and buying an older Vette and would be glad to offer my opinions to anyone who asks. I'd like to give back to the Forum to help repay all the great help and advice I've gotten so far. Thank you!
06-14-2017, 04:26 AM
#2
Melting Slicks
If you learn something from your mistakes or questions, they were not dumb. I am sure you will open a can of worms here about R 12 vs R 134. My experience has been that the mechanic is correct about leaking thru the hoses, which is why hoses today are different than the older stuff we try to keep using. If it was me, I would ask him to show you where the leaking was, usually a wet spot. Maybe even put a can of leak detector into the system, then use a black light to see where it glows. I had a leak in a car and could not find it unitl I put the detector in it. I immediately could see the glow in the condensation coming out of the car, which told me the evap coil was leaking. If the compressor is old, that could be a problem. If you switch over to R134, make sure you change out the orofice tube ( search for explaination why) and it will give you cold air, just like the old stuff. Also remember if you do all of the replacing that he suggests, and stick with the R12, you are locked into that for a long time, and while none of these products are going down in price, the R 12 is becoming more scarce and that is when the law of supply and demand take over your wallet. And maybe even get a second opinion, but I think he is correct, you just need to decide how much you want the AC and what you want to change out. Good luck.
06-14-2017, 07:08 AM
#3
Team Owner
Member Since: Jun 2000
Location: Southbound
Posts: 38,928
Likes: 0
Received 1,469 Likes
on
1,248 Posts
Cruise-In II Veteran
Your car uses the R4 GM compressor which are available rebuilt almost anywhere. R12 is still available to certified HVAC technicians. Your AC shop could replace the compressor and recharge the system with R12.
06-14-2017, 11:47 AM
#4
Former Vendor
Member Since: Aug 2006
Location: Jeffersonville Indiana 812-288-7103
Posts: 76,656
Received 1,813 Likes
on
1,458 Posts
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The best Freon for your car is R12... Expensive yes, but the best.
The only dumb questions are the questions that never get asked!
If the compressor is cooked, always replace the drier. The pieces from the compressor will end up inside it and it's always suggested to replace both when the compressor tanks.
To test the compressor to see if its working is tricky... You can test to see if the clutch engages, but that will not tell you if the compressor is working unless you have freon in the system.
To see if the compressor clutch is working, place the a/c in the on position. Then jumper the pressure switch and the clutch should engage.
- Willcox
Last edited by Willcox Corvette; 06-14-2017 at 11:47 AM.
06-16-2017, 10:43 AM
#5
Advanced
Thread Starter
this is a copy of an email I sent to Wilcox support to which I got a reply that said to post the info on the forum.
I believe we have been corresponding back and forth about my issue. When I initially test drove the car, the seller pointed out the "ice cold" A/C. Shortly thereafter, the A/C quit. On the advice of a my mechanic, I took it to a place that specialized in auto A/C. I think they filled it up with R124, perhaps did a cursory pressure test and sent me on my way. A/C quit shortly thereafter. It was coming into winter so I decided to take it back in Spring. I did so and the A/C mechanic said the compressor was toast and needed to be replaced with an overnight "vacuum test .He pointed to residue on the compressor housing and attached metal lines as evidence of leakage. He went on to illuminate me about the sizes of molecules in the different refrigerants. He said the new type (R134)has smaller molecules than the old type (R12). My regular mechanic and I followed your instructions and jumped the pressure switch and the compressor clutch engaged. We checked the green wire and it was sending 12 volts with the ac turned on. We couldn't tell if the compressor itself was actually running, However, I read elsewhere the pressure switch will not engage the clutch without sufficient pressure in the system. Since I believe there is no refrigerant in the system, I think there should be insufficient pressure for the switch to engage the compressor. Does this make sense? I'm not sure where to go from here, can you please point me in the right direction as I believe restoring the system to an R12 based one is the way to go if I can find a source if R12. I looked at rebuilt compressors and it was not obvious which to buy. The ac mechanic called his supplier who seemed to be confused which was the right compressor and threw out a range of $250 to $350 for one. That is way above what I find on the Internet for a rebuilt one. My current compressor is ACDelco P/N 14006785. Could you please tell me what I need to do at this point? As you know Corvettes run hot in the cabin and I've been boiling the last couple of days. I feel I'm being run over by the AC mechanic since I already gave him $200 on the first pass through his shop and I think he is taking advantage of me.
I believe we have been corresponding back and forth about my issue. When I initially test drove the car, the seller pointed out the "ice cold" A/C. Shortly thereafter, the A/C quit. On the advice of a my mechanic, I took it to a place that specialized in auto A/C. I think they filled it up with R124, perhaps did a cursory pressure test and sent me on my way. A/C quit shortly thereafter. It was coming into winter so I decided to take it back in Spring. I did so and the A/C mechanic said the compressor was toast and needed to be replaced with an overnight "vacuum test .He pointed to residue on the compressor housing and attached metal lines as evidence of leakage. He went on to illuminate me about the sizes of molecules in the different refrigerants. He said the new type (R134)has smaller molecules than the old type (R12). My regular mechanic and I followed your instructions and jumped the pressure switch and the compressor clutch engaged. We checked the green wire and it was sending 12 volts with the ac turned on. We couldn't tell if the compressor itself was actually running, However, I read elsewhere the pressure switch will not engage the clutch without sufficient pressure in the system. Since I believe there is no refrigerant in the system, I think there should be insufficient pressure for the switch to engage the compressor. Does this make sense? I'm not sure where to go from here, can you please point me in the right direction as I believe restoring the system to an R12 based one is the way to go if I can find a source if R12. I looked at rebuilt compressors and it was not obvious which to buy. The ac mechanic called his supplier who seemed to be confused which was the right compressor and threw out a range of $250 to $350 for one. That is way above what I find on the Internet for a rebuilt one. My current compressor is ACDelco P/N 14006785. Could you please tell me what I need to do at this point? As you know Corvettes run hot in the cabin and I've been boiling the last couple of days. I feel I'm being run over by the AC mechanic since I already gave him $200 on the first pass through his shop and I think he is taking advantage of me.
06-16-2017, 02:23 PM
#6
Former Vendor
Member Since: Aug 2006
Location: Jeffersonville Indiana 812-288-7103
Posts: 76,656
Received 1,813 Likes
on
1,458 Posts
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
First question is when you jumpered the pressure switch did the AC start to cool? If so then the issue is the pressure switch (which I doubt is the issue).
If you jumped the pressure switch and the compressor clutch engaged that means only one thing... the compressor clutch is engaging.
If your mechanic vacuumed down the system and it failed then obviously you have a leak somewhere. When ever we tear into one of these systems it's always a good idea to replace all the o-rings at each connection point. Depending on which Freon you use would determine which style o-ring you'd use.
At this point, I'd find a shop that you trust to put a set of gauges on the system to see if there is enough Freon to make the system run because my guess is that there isn't.
If they add Freon (which would be a waste if you knew the system failed the evacuation test) that still won't tell you if the compressor is bad. If the front of the compressor (R4 or radial compressor) is covered with oil, (and look at the underside of your hood). It's more than likely the front seal on the compressor is defective and a replacement is needed. We always do both the compressor and the receiver drier.
You can order one locally at your favorite parts store, the four season part number on the rebuilt unit is 57221 so any parts store should be able to cross that part number for you.
Getting one locally is the smart move because A) you'll probably get some kind of decent warranty, B) you don't have to pay shipping on the heavy compressor and C) you don't have to ship the heavy core back.
Willcox
If you jumped the pressure switch and the compressor clutch engaged that means only one thing... the compressor clutch is engaging.
If your mechanic vacuumed down the system and it failed then obviously you have a leak somewhere. When ever we tear into one of these systems it's always a good idea to replace all the o-rings at each connection point. Depending on which Freon you use would determine which style o-ring you'd use.
At this point, I'd find a shop that you trust to put a set of gauges on the system to see if there is enough Freon to make the system run because my guess is that there isn't.
If they add Freon (which would be a waste if you knew the system failed the evacuation test) that still won't tell you if the compressor is bad. If the front of the compressor (R4 or radial compressor) is covered with oil, (and look at the underside of your hood). It's more than likely the front seal on the compressor is defective and a replacement is needed. We always do both the compressor and the receiver drier.
You can order one locally at your favorite parts store, the four season part number on the rebuilt unit is 57221 so any parts store should be able to cross that part number for you.
Getting one locally is the smart move because A) you'll probably get some kind of decent warranty, B) you don't have to pay shipping on the heavy compressor and C) you don't have to ship the heavy core back.
Willcox
06-16-2017, 10:04 PM
#7
Advanced
Thread Starter
1979 A/C issue
First question is when you jumpered the pressure switch did the AC start to cool? If so then the issue is the pressure switch (which I doubt is the issue).
If you jumped the pressure switch and the compressor clutch engaged that means only one thing... the compressor clutch is engaging.
If your mechanic vacuumed down the system and it failed then obviously you have a leak somewhere. When ever we tear into one of these systems it's always a good idea to replace all the o-rings at each connection point. Depending on which Freon you use would determine which style o-ring you'd use.
At this point, I'd find a shop that you trust to put a set of gauges on the system to see if there is enough Freon to make the system run because my guess is that there isn't.
If they add Freon (which would be a waste if you knew the system failed the evacuation test) that still won't tell you if the compressor is bad. If the front of the compressor (R4 or radial compressor) is covered with oil, (and look at the underside of your hood). It's more than likely the front seal on the compressor is defective and a replacement is needed. We always do both the compressor and the receiver drier.
You can order one locally at your favorite parts store, the four season part number on the rebuilt unit is 57221 so any parts store should be able to cross that part number for you.
Getting one locally is the smart move because A) you'll probably get some kind of decent warranty, B) you don't have to pay shipping on the heavy compressor and C) you don't have to ship the heavy core back.
Willcox
If you jumped the pressure switch and the compressor clutch engaged that means only one thing... the compressor clutch is engaging.
If your mechanic vacuumed down the system and it failed then obviously you have a leak somewhere. When ever we tear into one of these systems it's always a good idea to replace all the o-rings at each connection point. Depending on which Freon you use would determine which style o-ring you'd use.
At this point, I'd find a shop that you trust to put a set of gauges on the system to see if there is enough Freon to make the system run because my guess is that there isn't.
If they add Freon (which would be a waste if you knew the system failed the evacuation test) that still won't tell you if the compressor is bad. If the front of the compressor (R4 or radial compressor) is covered with oil, (and look at the underside of your hood). It's more than likely the front seal on the compressor is defective and a replacement is needed. We always do both the compressor and the receiver drier.
You can order one locally at your favorite parts store, the four season part number on the rebuilt unit is 57221 so any parts store should be able to cross that part number for you.
Getting one locally is the smart move because A) you'll probably get some kind of decent warranty, B) you don't have to pay shipping on the heavy compressor and C) you don't have to ship the heavy core back.
Willcox
There was no cool air coming out of the vents. I have met with my regular mechanic and he agrees with you 100%. I have set up an appointment next week to bring the car in to do the work you suggested. I hope to be able to get back to you with positive news.
Phil
06-22-2017, 07:53 AM
#8
Advanced
Thread Starter
C3 A/C Issue update
Thanks Wilcox,
There was no cool air coming out of the vents. I have met with my regular mechanic and he agrees with you 100%. I have set up an appointment next week to bring the car in to do the work you suggested. I hope to be able to get back to you with positive news.
Phil
There was no cool air coming out of the vents. I have met with my regular mechanic and he agrees with you 100%. I have set up an appointment next week to bring the car in to do the work you suggested. I hope to be able to get back to you with positive news.
Phil
Phil