I drove my coupe home from work roughly two weeks ago, AC blowing cold. Went to take it for a drive today, AC compressor not engaging. I put my manifold set on and low side pressure is still 34, same as when I serviced it this spring. I cannot find anything that tells me what fuse and relay are for the compressor. I set it to defrost, still no compressor engagement. Any ideas would be greatly appreciated.

 

don't forget if you start to overheat ac is switched off.

John

 

The relay in passenger side fuse box is related.

 

If your low side is 34 without the compressor clutch engaging your system is probably way low on gas. R134 will have a much higher static pressure than 34 psi unless your outside temp is really cold.
compressor will not engage if you have a low or no r134 in system.

 

X2 on the low pressure. Without the compressor running, low side and high side should be about equal, and about the same pressure as ambient temp.

 

Why not try the system self test. All the necessary detail is here, starting at page 11.

https://redirect.viglink.com/?format...iagnostics.pdf

 

I did the self test and got codes 14&23. I getting no temperature input on my ELM327 dongle when running. I have no clue where the temperature sensor is, as for the gauge, it reads consistently. I'm going to attempt putting more R134A in the system and see what happens. Should the pressure cycling switch be jumpered?
Thank you,
Chip

 

It won't take any refrigerant, I got to the pressure cycling switch, unplugged it and the inside is oily. I'm going to try jumpering it this next weekend.

 

I think that if the temp sensor is faulty the compressor clutch will not engage.

 

For getting freon in where the compressor is not triggering, I put the refrigerant can in a tub of hot water after piercing, bottom down in the water. The hot water raises the pressure inside the can, and helps it overcome the pressure in the system. This is especially useful if the ambient temp is hot. That might be enough pressure difference to get most of a can in, and by then you might have enough pressure in the system to trigger the compressor. I use this trick for all my AC work here in Vegas. You'll need a fresh pot of water for every can of freon, as the gas transfer cools the can and the water. Really hot tap water will suffice.

 

Thank you, I'll try and give that a shot, possibly this evening if I get the primer work done on another car.

 

Welp, looks like the alternator is the priority on it in the near future. Had to stop at storage to rob the battery for my TR6 to make it home. Both batteries are on chargers and I'll check possibly tomorrow evening to see if the alternator is kaput. No shop therapy this evening.

 

STOP
If you are reading 32 without the compressor turning YOU HAVE A LEAK and theres not enough pressure to engage the clutch. Jumping the clutch will only burn out your compressor as YOU ARE LOW ON REFRIGERANT!

Look for the leak. there should be oil at the leaky spot. fix the leak. You may be low on oil to since the oil is carried by the refrigerant. So find out how much oil you need and add it. Change your filter/drier/desicant bag or whatever you have as you may have moisture in the system. Prob not if there was till some pressure

Once the leak is fixed and you added some oil if needed, do a good long vacuum (an hour or more) then hook up a can of refrigerant. The can will be pressurized to 70psi or so so it WILL FLOW INTO THE SYSTEM and the clutch should engage one theres enough residual pressure to trip the pressure switch

 

It was a serious case of stupid, I was so aggravated, I didn't open the low pressure quick connect, it was still showing pressure in the manifold set lines from the car I messed with over the weekend. Pulling the alternator was a bust tonight, someone has been in there before and rounded off the head of the top bolt. I get to go tool shopping tomorrow for whatever tool appears to might be able to do what I need.

 

lol. Btdt! Ok good. Whew! Ok. Rounded bolt first. Then on to the AC! I just fixed the AC in my S type R a weekend or so ago and its blasting cold air so when you hey back to it, I can help possibly!

 

Thanks! The alternator is kaput, not rebuildable. I've ordered a new one, now to wait. I've got plenty other projects in the meantime. AARCuda? 340, 4 speed and exhaust exits in front of the rear tires?

 

yup. Heres mine.

 

That's awesome! I can't say the last time I seen one, especially that color.