'98 A/C Compressor on 24/7 - Thoughts

[juniorwatson]

Guys,
I just finished doing an A/C system service by replacing the condenser, orifice valve, accumulator, low pressure switch, compressor and O-rings & PAG46 oil. I flushed the system, and then used a vacuum pump for an hour. The system then held -30 pounds for an hour.

I started off with one can, charging with the liquid 'till empty. I then started the engine, and the compressor clutch was engaged. I then finished adding the second can. I noticed that the compressor clutch never kicked in our out.

I then pulled the low pressure switch on the accumulator, and the clutch stays engaged. The head unit on the dash has the A/C button OUT/OFF. The blower motor is OFF.

I pulled the connector from the compressor receptacle, and it's got voltage.

I can pull the relay, and the clutch will disengage.

I have no idea why the compressor is getting the signal to engage the clutch 24/7.

Thoughts? I have absolutely no idea on this on. - TIA!

 

[east302]

Have you tried a new relay?

It looks like the VCM provides a ground to energize and switch the relay based on several inputs.






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[juniorwatson]

Have you tried a new relay?

It looks like the VCM provides a ground to energize and switch the relay based on several inputs.

Yes, I should have noted that before, I have swapped relays out, and no change. For some reason the relay is getting a GND signal to be energized and provide voltage to the compressor.

Any more ideas? The only other note is that the truck is got a current draw on the cable to the fender mounted fuse box. I'm wondering if something could have shorted in that fusebox?

Thx!

 

[juniorwatson]

Yes, I should have noted that before, I have swapped relays out, and no change. For some reason the relay is getting a GND signal to be energized and provide voltage to the compressor.

Any more ideas? The only other note is that the truck is got a current draw on the cable to the fender mounted fuse box. I'm wondering if something could have shorted in that fusebox?

Thx!

Well as a follow-up, I've fixed the problem.

I'm not sure what it was in the PCM, but I flashed the PCM with a few different programs, and now everything is working properly.

I haven't yet seen the clutch disengage while I had it sitting in the driveway, but the HVAC control engage/disengage the clutch as it should.

I can't explain that one....

 

[east302]

Glad it got sorted out, thanks for the update.


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[liquify33]

Question for you, I’m looking at the same work, after we move houses...

If I replace condenser, compressor, drier and orifice tube, do I need to add additional oil?
I’m going with a Sanden replacement compressor (prefilled w/oil) not sure how much ATM.

The system calls for 8oz.

 

[willxfs]

Yes. Glad you got it fixed up. I had a relay weld up inside causing a permanent connection one time. The compressor would never turn off and freeze up the system. Recently, I had a bad switch on the accumulator causing the system to freeze up.

 

[east302]

Question for you, I’m looking at the same work, after we move houses...

If I replace condenser, compressor, drier and orifice tube, do I need to add additional oil?
I’m going with a Sanden replacement compressor (prefilled w/oil) not sure how much ATM.

The system calls for 8oz.

The spec says that 3 oz is added for evaporator replacement, so if you’re replacing the hoses and everything but the evaporator then (by my math) you would add 5 oz to the system for an 8 oz total (no rear air). You would drain the compressor oil first, they usually include instructions for doing this with the compressor.








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[liquify33]

My compressor is the belly leaker type and on its way out.
I am not sure how reliable any measurement of oil will be when I drain it.

 

[96-2D-Hoe]

My compressor is the belly leaker type and on its way out.
I am not sure how reliable any measurement of oil will be when I drain it.

Get yourself a flush kit and flush the evaporator and lines. Drain the compressor and add the full 8 oz.
Edit.
But as you're changing the compressor... You should check what oil it uses and add that.

PS.
I was interested in the Sanden and I'd be curious to know how yours turns out. FYI I noticed there's a lot of 'Sanden' type knockoff's around and a genuine compressor made by Sanden is a fair bit more expensive. But probably worth it as they are a reputable company.