A/C blows warm at idle

[armandodiaz]

Any ideas?
I have replaced the compressor because of a leaking front seal. I have fully evacuated the system for an hour but it blows warm until I get it up to 3500RPM then it starts to cool.

[AaronM]

Originally posted by armandodiaz
Any ideas?
I have replaced the compressor because of a leaking front seal. I have fully evacuated the system for an hour but it blows warm until I get it up to 3500RPM then it starts to cool.

What's the charge level of the refrigerant? What's your low-side PSI at idle?

[armandodiaz]

I don't remember the pressures off-hand. I am wondering if I put too much oil in when I installed the new compressor. Is there anyway to tell? If I remember correctly I put 8oz in the compressor and about 1 oz in the dryer.

[bearone2]

check the hi and lo pressures when running and the fan on 4.

[armandodiaz]

Did some diagnosing this weekend.
The pressures are at 80 low 90 high. When I rev it up the pressure goes 40/120.
There seems to be knocking at the compressor (reman compressor, 2 months old).
The oil that came out when I took my hoses off, was black.

[AaronM]

Holy crap! 80PSI low side?! You're about 55PSI over-charged.

[armandodiaz]

I had that on my mind, until I heard the compressor knocking. Where is the expansion valve located?

[bazar01]

When idling, low/high side should be about 40/150 psi with compressor engaged and cooling fans running.
When reved, low/high should be about 30/200 psi.

Your compressor is shot! might as well replace txv and drier and flush system before installing new components.

[armandodiaz]

R134a

[bazar01]

Location of components:

Expansion valve in front under the fresh air blower below the windshield.
Not sure if you can pull the expansion valve sensing bulb which is clipped to the coil return line.

[armandodiaz]

So how do I get to it?
Do I get it from under the hood or under the dash?
BTW I don't think it matters but I didn't mention that it's an 87na.

[armandodiaz]

The rebuilder is exchanging the compressor, but I'm not taking any chances and also replacing the ex-valve and dryer. I'm also going to try and clean the system with brake cleaner and an air compressor.

[schmedes1]

That's a good move. Anytime the compressor gets changed, the rcvr/dryer (accumulator) and exp-valve (o-tube) should also be replaced for sure. I would suggest you find a proper a/c flush that is compatible with the refrigerant you intend to fill with and blow it through the pipes while the compressor and R/D are out. Brake stuff is very harsh and could hurt your o-ring/seals, creating a micro crack and a mystery leak somewhere down the road.

[armandodiaz]

Thanks for the advise I'll stop by the local parts place and see what they have.
So, nobody has told me where to locate the exp-valve? From the pic it looks like I should go from under the hood.
Last night I took my glove box off and all I could see was the heater core.

[schmedes1]

I have never had to replace mine (yet). BTW, the evaporator is always outside of the heater core from the perspective of the passenger compartment. You were probably looing at the evaporator, meaning that the exp-valve is to the right & slightly above. The most direct way to get to the exp-valve is from the cowl of the engine compartment. It is on the left (passenger side) of the blower/evaporator assembly. Of course, that is a lot more work and disassembly. Hopefully someone with more practice can fill in the blanks.

[bazar01]

The pic is looking from the engine compartment plastic cowl just below the windshield beside the battery..
You may need some crawfoot wrenches to get it out.

[bazar01]

You can also buy flushing solvents and kits from an air-conditioning supply house like CC Dickson or at auto air-conditioning shops.