I am no expert but first you can't run with a paperclip. The a/c compressor cycles on and off. There is a thermister that is hooked up to the ECU. I assume (based on your location) this thermistor is saying to the ECU no need to turn on as the temp is already low enough. Hopefully this is the case and you are just chasing your tail a little bit by trying to make it work in the middle of winter? Some of the techs on this forum may have some more definitive answers but I would wait til it gets warm to check it. If you put the defroster on the a/c should kick on some though. Have you tried that?

 

Thanks for the response. I've only used the AC on defrost with the heat on, and that's the problem the compressor does not come on. I'm not actually trying to use the AC to get cold air in the winter.
However it should engage when used to defrost the windows, or even just to quickly spread heat through the cabin using the panel vents, shouldn't it?
That's how I noticed the problem. Despite the AC light coming on when I select it, the compressor never engages, the engine's idle never fluctuates, and the rpms don't change either, and all that should happen if I change from the defrost settings (which automatically use AC) to a non-defrost setting and turn OFF or ON the AC.

 

check the wiring... probably a broken wire somewhere or a rusted contact.

 

I'm not an expert on this particular system but depending on the temperature outside it may or may not run the A/C.

I mean; your fridge is not continuously running the compressor to keep it cool, so if you plugged the fridge outside in the winter the frequency would decrease (if it's cold enough it wouldn't even come on). Despite the insulation.

You should not run with a jumped the relay. If you continuously run the compressor then you run the risk of damaging the A/C system. A/C systems like I mentioned before are not designed to run the compressor continuously like this: they cycle (but not short cycle).

I wouldn't bother tackling/testing this in the winter. Wait until it's warm out to see if it will kick on quickly to determine if you actually have a problem with the system.

Also I don't bother using AC with hot heat for defrost. For light moisture I use a/c on, max cold, max blower, windshield. De-humid is a/c on, max cold, vent setting: feet, forward or both and on re-circulation*.

 

could be switch or wire. Also there is a pressure switch. That is supposed to protect the compressor from running with not enough refrigerant. Another good reason not to jump the relay! Maybe low refrigerant?

 

Thanks for the responses!

Most if not all modern cars do not give you a choice about using the AC when defrosting windows. They always have the AC used in the Window defrost, and window-floor split defrost settings. FORD, Chevrolet, Honda, Subaru, and Kia all work this way and I think it's the same for all cars of the last 10 years. I assume Toyota also works this way.

The AC works to defog or defrost windows and of course it works while the temp dial is set to heat or maximum heat. I'm not trying to get the AC to run cold air in my car when it's -25 already outside.
I'm trying to get the compressor to engage like it supposed to, when I'm using the car's heat, to defrost my windows.
The system has been been checked and is not low on refrigerant, and as I stated before if it was a problem with high or low pressure sensors, it would have been them that I needed to bypass, not magnetic clutch relay, right?

 

Correct all cars made in the last 15+ years engage the AC when you use the defroster no matter the temp and you have NO control over this, because the AC system will DRY the air and thus defrost water droplets on your windows.

Now jumping the compressor just means the clutch works, Not sure how you can tell if your charge is OK because the only way to tell if you have a full charge is with the compressor running?? soooooo......

Because jumping the compressor litterally goes around ALL systems including the hi low sensors.
You may want to check them.
Then get a pin out for the relay and see if the relay is getting power.
Then jump the correct pins on the relay socket and see if it engages.

You just have to work backwards on each system to find where you loose signal.

 

I checked the charge level after bypassing the relay so the compressor would engage, and once I had the compressor going, the gauge indicated that I was low on the refrigerant. (Without the compressor running the gauge always read as the system having nominal refrigerant)
Now that I knew the system was low, I started to top it up, but as soon as I added more refrigerant (with the compressor running at max) it started escaping out the bottom of the compressor in random blasts of high pressure.
I'm assuming that means the compressor itself is shot. I don't know much about it. Does the compressor have seals that can give out, and if so can it be resealed? Or does this mean what I fear, that I need a new compressor?

 

Sounds like your compressor has a leak. This might explain why it won't come on unless you bypass the relay, because if it's low on the "freon" as the result of a leak, then it has a safety mechanism to prevent it from turning on. You can get a new Denso compressor online for so cheap, that you might as well just replace it instead of trying to fix a leak on an already used or worn compressor. Check Amazon and/or Ebay. I recommend a new, not rebuilt compressor (if that's what the problem is).

 

check the o rings on your inlets.