NEED HELP Oil Pressure Drop Concurrent with A/C Disengagement

[therealsethallen]

So, here's a weird one.
I've been driving the Volvo for the best part of the month and the truck has been parked for at least a week and a half. I got in the truck today, went to get a cold drink up the street. I shut the air conditioning off to talk to a friend in the parking lot at idle. Idle dropped considerably, and the Oil Pressure Gauge dipped, and recovered. I did this again when I got home to see if it was a pattern thing, or intermittent. It did it two out of the three times I tried it. Took the truck for a drive with the A/C off, and it didn't drop once.

I did clean the throttle body last weekend, and run half a can of SeaFoam through the fuel system.

One thing I will say, is that even properly charged, the A/C has always been sub par in this truck. I'm curious if it's just the compressor locking itself up.

See, video for the exact issue.

 

[Tiggerr]

I'm sure there's prob 100 threads about this out there... seems to be a quirk of these trucks..

my Rainier will do that on occasion... usually when it's really hot out...

the oil pressure drop is from the drop in RPM at idle...not anything mechanical...

I've have yet to see a real solution for this... usual things like cleaning the TB resetting PCM...etc seem to have no effect...
my better halfs old 04 Malibu used to do it too... never could find out why...even when it was under warranty Chevy dealer could never figure it out either...

 

[therealsethallen]

I have a feeling this year will be the last running this A/C compressor. It's marginal at best, and I've leak checked the system twice no no avail. The compressor is the last part that isn't new. Guess I'll just live with it for the summer and pray I make it into winter.

 

[Mooseman]

It could also mean the throttle needs cleaning but I'm sure you knew that.

Don't mind the oil pressure gauge. It's fake. If you don't get a warning on the DIC, don't worry about it.

Some do it, some don't. Just the nature of the beast. Or possibly the compressor has an excessive resistance and needs more power to run, possibly due to age or overcharge.

 

[therealsethallen]

I had problems with A/C over-cycling all last summer. At this point I feel stupid if I don't believe it's the compressor. I dumped $150 into the A/C last summer for lukewarm cooling.

 

[Tiggerr]

Idk your AC should cool fine if the charge was done right...and all else is well.. idk what all you replaced....I've never had a compressor be "weak" they're usually good or not

I had the usual clutch cutout when in the 80's or better, pulled the Shim out of the clutch and that stopped..

I've had my Rainier for 4 1/2 yrs and never touched the AC so far other than the clutch shim...and with 176K on it it blows ice cold..

 

[Mooseman]

Come to think of it, you're right. Our compressors are the screw type. I was thinking of the old piston type. However, it may be possible that if it's overcharged that it's loading down the compressor more.

 

[JerryIrons]

I'm in the same camp in regards to the oil pressure light...doesn't mean anything to me, could even be crappy gauge, wiring etc. Engine codes are more important. Also your compressor, have you put a manifold gauge set on it, and made notes of the pressures? They are pretty good indicator of how things are running...and if the specs are out of desired range you have some troubleshooting steps to narrow things down. I've had to change out 2 compressors in my 256k 06 4.2 ext, first one the compressor died, 2nd one the front clutch got so bad I had to hit it with a piece of wood to start the compressor running.