Just finish an install changing out compressor, condenser, and expansion valve. It is 65 degrees and my pressures are 20 low side (with fluctuations down to 12) and 90 on high side. It's blowing ice cold as it should but clutch and fan stays engaged while the a/c is on.

This is a dumb question but on the 04 is the clutch supposed to stay engaged? It's puzzling me because I put 19 oz in and the install when good. No leaks or anything.

Initially I changed the original compressor because it was leaking so the owner wanted to change it all out. The only thing I didn't change was the switch because the owner forgot to get one, which now I think I should of took my lazy *** down to the store and picked one up. Now I'm thinking this was the initial issue in the first place which caused the original compressor to go bad. Thoughts?

Car has 106k on it but looks like hell with a lot of oil leaks.

 

I once had a 2003 4-cyl and the AC compressor cycled on & off just like you'd expect. I don't imagine the 2004 is any different as far as that goes. I no longer have the shop manual for that generation.

IIRC there's more than one "switch". Which were you referring to? There's pressure switches to prevent the compressor running when the refrigerant pressure is too low or too high. Those aren't responsible for the normal compressor cycling - pretty sure that is done by a temperature measurement in the evaporator.

Have you checked whether the clutch is just seized? Backprobe the connector for the clutch to see if it's getting "commands" to cycle (in the form of getting battery voltage then not).

 

I'm assuming the pressure switch on the condenser is what tells the pcm to ground. As of now it seems like there's constant ground and it's not the compressor because I tested it before installing to make sure it was good. I guess tomorrow I'll install a new switch and start testing from the PCM.

 

I don't know how the PCM is programmed to work the a/c compressor. I'll assume the a/c pressure switch and the evaporator temperatures will dictate if the compressor needs to be shut off. Outside of those inputs, the 04 may not cycle the compressor. I know in Houston, the weather is usually so hot, my compressor doesn't shut off on my 05 TSX.

The a/c pressure switch will open circuit when the pressure is below 28 psi or above 455 psi. The pressure switch is on the high pressure line, so the pressure switch may be working properly. The red/blu wire should have greater than 5V. The switch itself should have continuity across the pins when the a/c pressure is between 28 and 455 psi. The pins should be an open circuit outside of those pressures. The pressure switch sends 5V to the HVAC unit when pressures are normal, and doesn't send 5V when the pressures are outside the operating range.

I don't know what temperatures (high or low) on the evaporator temperature sensor will cause the compressor to shut off, if any.

You may want to check the HVAC for codes. I have a writeup in that common diy thread on how to do this.

 

I've been doing some testing and the voltage is correct. I think nothing is wrong with the system unless the clutch is suppose to cycle. I forgot I dropped the manifold I'm using doing my last job so that is why my pressures are off. Hooked up my other set and pressures are normal. I'm just lost as to why it's not cycling. I haven't worked on a system that doesn't especially Honda.

Now I'm planning on getting a replacement compressor in the morning to see if it does the same thing.

 

To close this out. Decided not to get another compressor and double checked the PCM (supplies ground to relay) and checked thermistor. Both checked out ok. I went to the junk yard and got a thermistor just to see if anything changes. Installed it and after sitting idle for around 45 mins the compressor clutch started to cycle. So it was either impatience on my part or thermistor was actually bad after it checked out good on the ohm meter.

This confused me because I just changed out my 07 accord ac system and it started cycling immediately like all the other cars I work on.