HVAC controller relay - AC Trouble shoot
05-14-2006, 11:20 AM
#16
Owns the Streets
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There's a sight glass for the AC.
Think It's passenger side front. Behind the headlight bar and in front of radiator.
But that won't help if AC isn't running.
Was also advised that my 134A system doesn't bubble up like R-12.
Radio Shack used to sell DPDT 5 amp mini relay.
I was able to tuck it under the HVAC control board. There's not much room where
the original relay sits.
http://www.radioshack.com/product/in...entPage=search
Ernest (NYC)
Think It's passenger side front. Behind the headlight bar and in front of radiator.
But that won't help if AC isn't running.
Was also advised that my 134A system doesn't bubble up like R-12.
Radio Shack used to sell DPDT 5 amp mini relay.
I was able to tuck it under the HVAC control board. There's not much room where
the original relay sits.
http://www.radioshack.com/product/in...entPage=search
Ernest (NYC)
05-14-2006, 12:08 PM
#17
Pro
Thread Starter
Many issues to sort out
Hi All,
I Bill, Dave, Ernest and Jeff.
I will try and clarify where I am at in the process.
The car has never had AC for me. Clutch has never engaged
I had a shop look at the AC but this was one of many jobs being done. They seemed to think that the relay was bad and had removed the controller. But I can hear it actuate. So before I replace it I was wondering if there was a way to check for continuity from outside the controller... sounds like I may be able to do this at the fuse panel?
THe valve and diaphram was replace during the stay at the shop. So the water problem has been fixed.... I had the HVAC controller unit out when I started this post... when I plugged it in yesterday all was well. ( I will edit the post above)
The fan is probably as dirty or worse than the rest of the car when I bought it so I will try and clean it. Thanks Dave.
So I will read though wally's post and look for check points.
I guess my plan is to replace and re-oring what is needed in the AC system
The car had a lot of oil on the front of the engine from a pan gasket seep. I have cleaned it all up long ago. The compressor may have leaked at somepoint because it was way dirty too...
I took it down and cleaned it up a bit but I will probably need to replace it too.
any one use the Kuehl unit from griffiths or is the nippondenso unit the best? any comments on replacement of the AC plumbing. (any comments on R134 upgrade)
Thanks for the help on this.
LO
I Bill, Dave, Ernest and Jeff.
I will try and clarify where I am at in the process.
The car has never had AC for me. Clutch has never engaged
I had a shop look at the AC but this was one of many jobs being done. They seemed to think that the relay was bad and had removed the controller. But I can hear it actuate. So before I replace it I was wondering if there was a way to check for continuity from outside the controller... sounds like I may be able to do this at the fuse panel?
THe valve and diaphram was replace during the stay at the shop. So the water problem has been fixed.... I had the HVAC controller unit out when I started this post... when I plugged it in yesterday all was well. ( I will edit the post above)
The fan is probably as dirty or worse than the rest of the car when I bought it so I will try and clean it. Thanks Dave.
So I will read though wally's post and look for check points.
I guess my plan is to replace and re-oring what is needed in the AC system
The car had a lot of oil on the front of the engine from a pan gasket seep. I have cleaned it all up long ago. The compressor may have leaked at somepoint because it was way dirty too...
I took it down and cleaned it up a bit but I will probably need to replace it too.
any one use the Kuehl unit from griffiths or is the nippondenso unit the best? any comments on replacement of the AC plumbing. (any comments on R134 upgrade)
Thanks for the help on this.
LO
05-14-2006, 12:53 PM
#19
Rennlist Member
Loren,
In order to protect the controller relay, I piggy-backed an external relay which I located near the jump post in the engine compartment. I also rigged the aux. fan to come on with the AC. After replacing a dying battery everything works great. I had recently switched to R134 and wanted to maximize the heat transfer at the condensor by revising the fan setup. Mine is an 84, yours may be different. If your have an auxilliary air valve clamped onto the cross brace, it has two wires, one a ground; the other wire goes hot when the AC clutch is engaged. It raises the RPM to compensate for the compressor load.
Here's my setup:
https://rennlist.com/forums/928-forum/270408-a-c-control-relay-modification.html
Good luck,
Dave McK.
In order to protect the controller relay, I piggy-backed an external relay which I located near the jump post in the engine compartment. I also rigged the aux. fan to come on with the AC. After replacing a dying battery everything works great. I had recently switched to R134 and wanted to maximize the heat transfer at the condensor by revising the fan setup. Mine is an 84, yours may be different. If your have an auxilliary air valve clamped onto the cross brace, it has two wires, one a ground; the other wire goes hot when the AC clutch is engaged. It raises the RPM to compensate for the compressor load.
Here's my setup:
https://rennlist.com/forums/928-forum/270408-a-c-control-relay-modification.html
Good luck,
Dave McK.
05-14-2006, 02:51 PM
#20
Rennlist Member
Loren, a quick way to check the operation of the relay with everything assembled is to look for the +12V at the freeze switch when the HVAC controller calls for AC. If you're not getting that and the fuse is good, you may have a bad relay. Assuming your wiring isn't hacked...
05-14-2006, 10:05 PM
#21
Pro
Thread Starter
still a little warmer than outside air.
So maybe I should try to get one of those manual shutoff valves or try zip tying it shut. The car is a little bit warmer then the outside air.
I have a new vacuum actuated heater valve. But it seems that even a good working one may have some leakage.
I need to clean out the vent system. it looks pretty grungy from out here.
any suggestions?
I will get a mityvac somewhere. Any suggestions on a bay area location? Or internet site?
I have a new vacuum actuated heater valve. But it seems that even a good working one may have some leakage.
I need to clean out the vent system. it looks pretty grungy from out here.
any suggestions?
I will get a mityvac somewhere. Any suggestions on a bay area location? Or internet site?
05-14-2006, 11:05 PM
#22
Burning Brakes
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Originally Posted by lorenolson888
So maybe I should try to get one of those manual shutoff valves or try zip tying it shut. The car is a little bit warmer then the outside air.
I have a new vacuum actuated heater valve. But it seems that even a good working one may have some leakage.
I need to clean out the vent system. it looks pretty grungy from out here.
any suggestions?
I will get a mityvac somewhere. Any suggestions on a bay area location? Or internet site?
I have a new vacuum actuated heater valve. But it seems that even a good working one may have some leakage.
I need to clean out the vent system. it looks pretty grungy from out here.
any suggestions?
I will get a mityvac somewhere. Any suggestions on a bay area location? Or internet site?
05-14-2006, 11:09 PM
#23
Rennlist Member
Loren,
You need to figure out if your AC is cooling at all. Feel the pipes under the windshield wipers and see if they're cold. If they are not then you are not cooling and it might not be the heater valve.
Dave McK.
You need to figure out if your AC is cooling at all. Feel the pipes under the windshield wipers and see if they're cold. If they are not then you are not cooling and it might not be the heater valve.
Dave McK.
05-14-2006, 11:20 PM
#24
Burning Brakes
Join Date: Oct 2004
Location: Suburban St. Louis in Illinois.
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Dave...if his clutch is NOT engaging....then its NOT cooling at all. The hot water issue is vaccuum related...but not the lack of compressor function. He has 2 totally different...but simultaneous problems in the same component....(and thats without ruling out defective vaccuum actuator diaphrams, which are almost a "given" on these cars...unless documented inspection and replacement/repair has already been done)... 
05-15-2006, 01:00 AM
#25
Owns the Streets
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Got my MityVac unit from 928Specialists.
About same price as Harbor Freight. And I'm supporting a 928 vendor.
Just don't like the idea that the AC has never been operational.
Who knows what the PO has done, or rather neglected to do, to the AC system.
Is there any way to check for freon leak if there's none in the system?
There are dye systems that was suggested to me.
Inject dye into the system and then trace with them funky orange glasses and blacklight.
May the fix not be a major wallet shrinking exercise.
Ernest (NYC)
About same price as Harbor Freight. And I'm supporting a 928 vendor.
Just don't like the idea that the AC has never been operational.
Who knows what the PO has done, or rather neglected to do, to the AC system.
Is there any way to check for freon leak if there's none in the system?
There are dye systems that was suggested to me.
Inject dye into the system and then trace with them funky orange glasses and blacklight.
May the fix not be a major wallet shrinking exercise.
Ernest (NYC)
05-15-2006, 02:13 AM
#26
Rennlist Member
The relay sends +12V first through the freeze switch, then to the CE panel on K21. After that it exits at M12, goes through the low pressure switch, then through the 14-pin connector to the AC clutch & air solenoid.
It sounds as if you are going in a couple different directions here. IMHO you need to settle down and attack one problem at a time.
The Refrigeration system may be completely empty. I'd say replace all the O-rings then take it to San Carlos Radiator -- Big Dave will take good care of you, he has an excellent leak detector he can use to tell you if it's leaking anywhere else, like at the compressor. You can verify whether the system is empty by lightly pressing one of the AC service valves -- they are kind of like an oversized tire valve. If you press the center on the valve and do not hear gas escaping(at least as much as you'd get from a tire) then the system is empty and you can do damage if you do run the compressor for any length of time. You could temporarily bypass the low pressure switch to verify that the rest of the electrical works, but only bypass it long enough to verify the compressor turns.
The electrical/vacuum end of the system is another issue, and there may be nothing wrong besides the relay, or maybe nothing at all.
Without the AC you will generally get warm air from the vents, especially if you are missing the seal at the rear of the engine bay that keeps hot air from being sucked up by the HVAC blower.
It sounds as if you are going in a couple different directions here. IMHO you need to settle down and attack one problem at a time.
The Refrigeration system may be completely empty. I'd say replace all the O-rings then take it to San Carlos Radiator -- Big Dave will take good care of you, he has an excellent leak detector he can use to tell you if it's leaking anywhere else, like at the compressor. You can verify whether the system is empty by lightly pressing one of the AC service valves -- they are kind of like an oversized tire valve. If you press the center on the valve and do not hear gas escaping(at least as much as you'd get from a tire) then the system is empty and you can do damage if you do run the compressor for any length of time. You could temporarily bypass the low pressure switch to verify that the rest of the electrical works, but only bypass it long enough to verify the compressor turns.
The electrical/vacuum end of the system is another issue, and there may be nothing wrong besides the relay, or maybe nothing at all.
Without the AC you will generally get warm air from the vents, especially if you are missing the seal at the rear of the engine bay that keeps hot air from being sucked up by the HVAC blower.
