Couple Questions

Hey guys,
Not sure if this first question is electrical or not, but the oil pressure gauge in my cluster has decided to go all the way to the right at anything other than idle, and then at maybe 15 or so at idle. The aftermarket one that is hooked up reads about 25 at idle and 50-55 under load.
What could be going on with it?

Second question, my truck has A/C, I can see the compressor attached to the engine, and the HVAC control has the A/C, not sure if that matters, but the A/C will not do anything.
When the truck starts, the A/C light flashes for a couple minutes, then quits, if I push the button for A/C, the light flashes for awhile, but nothing happens, no cold air, no RPM drop, nothing.
Any ideas on this?

This is a 1993 K1500 with a 350.

Your controller head could be going out. Do you get fan and heat ? Also verify it has a good ground, especially if stereo has recently been changed. You also may want to check the connection at the compressor where the pressure valve hooks up. My connector occasionally pops loose on my 88.

You have a low charge in the a/c. Too low of a charge and it doesn't activate the low pressure switch.

Your oil pressure sending unit is taking a dump. Pretty common.

joep88cheyenne said:

Your controller head could be going out. Do you get fan and heat ? Also verify it has a good ground, especially if stereo has recently been changed. You also may want to check the connection at the compressor where the pressure valve hooks up. My connector occasionally pops loose on my 88.

Click to expand...

I have tried replacing the head unit already, no luck.
I have fan and heat/outside air.
Tho it does struggle with blending, i.e. when on defrost, it still comes out the regular vents.

skylark said:

You have a low charge in the a/c. Too low of a charge and it doesn't activate the low pressure switch.

Your oil pressure sending unit is taking a dump. Pretty common.

Click to expand...

Oh, good, why would the aftermarket unit be fine? Different reading?

un4givn85 said:

I have tried replacing the head unit already, no luck.
I have fan and heat/outside air.
Tho it does struggle with blending, i.e. when on defrost, it still comes out the regular vents.

Oh, good, why would the aftermarket unit be fine? Different reading?

Click to expand...

It is using a different sending unit.

I figured your aftermarket gauge was different sending unit. and I agree either oem sending unit going out or gauge is flaky, leaning towards the gauge.

Yeah need to check the charge in the ac system. and also the compressor clutch when ac is turned on to make sure it is locking into the compressor. if not the low pressure sender on back or near the compressor is not kicking in, keeping the ac from running.

I'll just ignore the factory gauge then.

Is the A/C charge easy to check, or is there a special tool?
As I mentioned earlier, the clutch isn't engaging when the head unit tells it to.

joep88cheyenne said:

Your controller head could be going out. Do you get fan and heat ? Also verify it has a good ground, especially if stereo has recently been changed. You also may want to check the connection at the compressor where the pressure valve hooks up. My connector occasionally pops loose on my 88.

Click to expand...

i have had that happen to me with the connector.