My AC compressor won't turn on. So far I checked the fuse. Fuse it fine. I checked for power on both sides of the fuse with a voltage test light and got some light so all is good there. When I turned on the AC in the car the radiator fan turns on and I hear a light clicking sound at the firewall behind the accumulator. I bridged the two points on the clip on the back of the compressor and the compressor still won't go on. I bridged the two points on the clip on the accumulator, same thing. I checked for power from both clips on the compressor and got nothing at all. No light.

So, I read some people replaced the compressor relay, where is the relay? And is there a fusible link? Is there anything else I should check?


Thanks

 

the 2 terminals on the rear of the compressor are for the 12V signal to activate the AC clutch, you should prob check to see that you getting the propper voltage if not id start tracing it back to the realy

 

need to check the charge of ac system.. im thinking low to no charge...

 

Right I checked the voltage on that terminal on the rear of the compressor, there was no power. And I didn't know where the relay was, but I found it, bought a new one this evening and that did not fix the problem.


One more note I forgot to mention. This is in my 87 Formula 305 4bbl. The engine along with the compressor was brought over from my 90 to my 87. The accumulator is the one that was already in the 87. There is currently no charge. The guy I was having charge it said the compressor was not kicking on and for me to bring it back for the charge after I got it to work. I understand that if there is too low pressure that it will not run but that I can bypass it, and I did, still nothing happened though.

So is there a fusible link?

 

there is the possibility of a fuible link, you should be checking the end of the plug not the pump, unless you have the plug connected to the comp

 

don't run the compressor with out a charge the refrigerant has oil in it to lubricate the compressor u can damage it very easily.

also the compressor clutch will not kick in unless u bypass the low pressure switch.. but it has to have a small charge

 

That just jogged my memory. My friend did put a small charge in, then we tried to turn it on and it didn't come on.

 

check the fuses?

 

Yep, in the first post.

 

Well, time to break out the diagrams and the test light and start tracing the signal.

http://www.austinthirdgen.org/mkport..._continued.gif

You can go forward or backwards, whichever you prefer. Just follow the path of the signal and try to find out where the 12V is interrupted.

Btw, according to the diagrams (which might not be 100% accurate, though), you should not have an A/C compressor relay, that was supposedly only for V6 engines. You probably have a blower relay, though. What wire colors are on that relay?

The diagram above should be very easy to read and should help you find the problem.

Let us know what you find!
Lou

 

Just a little food for thought... In order for the a/c system to actually take the charge, the compressor needs to cycle. If the pressure to too low to make the compressor kick on, it wont accept the charge, and the low side will just gain pressure.

Now...the low pressure switch, on the drier should kick the compressor on, but Ive seen it not do this. Sometimes you need to short the switch wiring, get the compressor running, then get your charge started.

If you have the a/c on, and short out that low pressure switch wiring, the compressor should run. If its not, then i would try applying 12v to the compressor clutch directly. You should see/hear a click and see the front of it move to lock up. If it doesnt, the clutch is shot. Ive seen that several times. Its just windings...they can go bad.

If the clutch is found to be working, and you still arent getting power down to the compressor with the low pressure switch wiring shorted, then Ide say you have an actual wiring issue. Broken wire, bad connection, mouse damage...

Like others have said...at that point, you'll have to start tracing back and checking everything.

J.

 

How do you apply 12v to the clutch?. Does everything need to be running, or can this be a static test. Does it require a 'hot' and 'ground' connection on the clutch terminals?.

Sara Lou

 

I had other things come up so I'll have to get back to this another time. Until then my car is sitting, I have other things to fix before I drive it more.

Thanks for the help so far. I'll post on this thread again when I get back to it.

 

Guaranteed your pressure is low. You have a low pressure shut off that is preventing the compressor from kicking over. Put in more freon, then look for leaks.

 

Well actually I have been under the impression, by many people, that if I stick a wire between the two contacts on the plug that goes into the accumulator it will bypass the low pressure and turn on whether or not there is freon in the system. I have done this and it still does not turn on. If that is the case that it should have turned on then I am convinced it its a wiring issue. I have replaced and tested just about everything else. The wiring in the car in some other areas was Micky Moused already by the previous owner so I'm sure it's wiring.
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By the way the relay I replaced earlier on was the blower relay.

 

is the compressor seized?

 

The engine, with this compressor was in my 90. The engine was pulled and put in the 87 with the compressor still on it. When it was all in the 90 it worked 100% perfect, never had a problem. When I bought the 87 the ac didn't work, the guy said it needed to be charged. But, that guy was a tard (you would have had to see the crappy repairs done before I got it) so it probably had bad wiring or something else.

You gotta understand, the previous owner ran wiring from each of the headlights to the fuse block and a toggle switch he put into the dash just because the headlight control module went bad. Then the guy put trans am tail lights on the car and screwed up the wiring there so all the lights in the car weren't working right. So those are the reasons I was looking at wiring and relays and such. I'm sure my compressor could go bad all of a sudden but I doubt it, that's too much of a coincidence.

And you're right about pinups, they're the best :-)

 

Haha yeah, pinups are great. As for the hack that had the car before you, sorry for your headache lol. In retrospect if you jumped the low pressure shutoff the right way then yeah I'd be looking at wires too.