TCCoA Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
166 Posts
Discussion Starter #1
a while back before i replaced my engine my a/c was working fine, then when i had it replaced it didnt work any more. I never bothered with it becuz it was cold but now its very hot out and i need the a/c to work. Does anyone have any ideas what might the shop had did to male it stop working or is there anyway for me to check it out myself without another shops help. I went to autozone and refilled the 134 in it and it was already fulled. Could it be the compressor?
 

·
Registered
Joined
·
3,178 Posts
If the R134a was fully charged and didn't leak out, then that eliminates one thing... I doubt very much that an engine swap would hurt the compressor...
Check the electrical connector to see that it's plugged in tight, maybe the compressor isn't getting the signal to turn on??
 

·
Registered
Joined
·
278 Posts
When you swap an engine, you have to purge the A/C system and disconnect the A/C lines. You probably just need some refrigerant in there

- Mark

EDIT- Ok, just read that you said it was already full. Did you swap the compressor from your old engine to the new engine? If not, its possible the compressor on your new engine is no good or perhaps the A/C system isn't pressurized correctly.
 

·
Whining Intakes Rock
Joined
·
3,645 Posts
Possibly.

Lots of components that could go wrong. First, verify if your a/c clutch is engaging. Have someone turn on the a/c, with the engine running, while you watch the compressor. If nothing happens, then one of two things: the magnetic clutch is shot or it's not getting power. You can verify with a voltmeter if it's getting power or not. If it is, verify the ground. Connect ohm meter to ground and the black wire on the connector. If it's 5 ohms or less then you have a good ground. More than that, you need to fix the open circuit. If ground and power is good the compressor may need to be replaced. If power is not there, you'll have to dig deeper. Easiest is to check fuses.

The PCM controls the clutch and can prevent the clutch from engaging at engine startup, high engine speeds, accelerating, engine is running too hot or low engine idle. Also A/C will not come on if ambient air temp is 45-50 deg. F. or below.

There is an a/c compressor cut-off switch located in the discharge line between the compressor and the condenser core. It's normally closed. It will open, shutting off your compressor if the head pressure rises to 420 psi. This same switch controls the high speed fan and is normally open unless discharge line pressure reaches 325 psi.

Next is a cyclic switch located on a schrader valve on top of the drier. Normally closed it opens when pressure drops to 22-28 psi in the drier. Ambient air temperature below 45-50 degrees F will prevent the cyclic switch from closing. The cyclic switch will send a signal to the constant control relay module (CCRM) which supplies the power to the clutch.

Properly diagnosing the A/C system requires a manifold gauge. But there are some things you can do with just a test light and ohm meter. If you have the SATC (semi-auto temperature control) I'd go get a shop manual and follow that to test your dash controls.
Using your test light or volt meter, check voltage supply at pin 2 of the dash a/c switch.
No: Check fuse 6 for power going to the switch. If that is fine, there is an open circuit between the fuse and switch.
Yes: Continue checking switch. Check pin 4 for voltage. If none, replace the switch.

Check cyclic switch: Remove cyclic switch connector. Start the engine. Put A/C to MAX A/C. Jump pin 1 of the cyclic switch connector to pin 2 at the cyclic switch. If compressor clutch engages, replace the cyclic switch. If not, check CCRM.

Checking CCRM relay: Turn engine off but leave key on. Check pin 21 for voltage. If not, find open circuit. If yes, check pin 23. If no voltage at pin 23, replace CCRM.
If there is voltage, then you need to check the power going to the compressor. Already mentioned that above.

Before you replace the compressor though, you should check your line pressures. This is where a manifold gauge comes in handy. Having too much is just as bad as having too little. You can take it to a shop and have the system evacuated and recharged to proper PSI.

There are other things to do if you have the semi-auto climate control but that will get you started.

Absolutely recommend you get a shop manual. It goes into much more detail.
 

·
Registered
Joined
·
3,178 Posts
Mark B. said:
When you swap an engine, you have to purge the A/C system and disconnect the A/C lines. You probably just need some refrigerant in there

- Mark

EDIT- Ok, just read that you said it was already full. Did you swap the compressor from your old engine to the new engine? If not, its possible the compressor on your new engine is no good or perhaps the A/C system isn't pressurized correctly.
You do?? I've pulled engines from MN12s before and never had to do this... unbolt it and slide it out of the way. No unhooking lines or any of that.
 

·
Registered
Joined
·
278 Posts
Silver95Bird said:


You do?? I've pulled engines from MN12s before and never had to do this... unbolt it and slide it out of the way. No unhooking lines or any of that.
Hmmm, go figure...Guess that was just something I had to do for my swap :)
 
1 - 7 of 7 Posts
Top