Background:

I have a 1994 V6 4x4 P/U. I recently got the AC working again, but during my repair I found that the PO removed quite a bit of the components. This includes the idle up VSV, thermistor, and AC amplifier. I have it wired now so that when the AC is turned on a thermostat makes sure it's not too cold and the AC pressure switch controls a relay that won't kick the compressor on unless there is enough pressure. Good enough right? Well, I am having idle issues, namely the truck nearly dies when the AC is on at idle. Today I acquired a used idle up VSV and plan to get it back in the system.

FSM schematic: http://personal.utulsa.edu/~nathan-b.../2aircondi.pdf

Questions:

The AC VSV appears to interact with the Engine Control Computer. Does anyone know what it tells the computer and can I bypass the wiring harness and just run 12v to the VSV when the AC is on?

The VSV goes to the harness at H and K1, is H +12v and K1 ground?

Thank you for any help.

 

OK, after checking the connections at the electrical connector on the VSV K1 is +12v whether the AC is on or off and H is not helpful because it is not connected to anything. It looks like I have to ground out H to turn on the VSV and that should have the desired effect (whatever it might be) with the Engine Control Computer. Thoughts?

 

You can ground it but it will turn the VSV and AC on all the time the engine is running.

The H wire (black and red) is ECU controlled and grounds both the VSV and the Pin 9 (H1) of the AC amplifier (wire is White and red)
The K1, Is B+ wire at the AC VSV is from IGN1 (key switch).

It does this for engine control eg. idle, decel, engine temp.

The H or H1 connects to the ECU at pin 24 of the C connector marked ACV (V6).

Also check the AC idle control speed knob on the AC element unit behind the glovebox, If its set to high your AC will never turn on unless the engine is revved real high or wont shut off at all during idle.

 

Thanks Punchy. I don't have an AC amplifier, so there is no AC idle control knob. I'm hoping to control the idle only with the VSV -- I guess we'll see. I think I will wire up the VSV to ground and splice into the +12v wire to the AC compressor. That way the VSV only comes on when the AC is on. I was just worried about the connection to the Engine Control Computer.

 

I hooked the VSV up to the +12v to the magnetic clutch and just grounded the other end. I can hold an idle of 1000RPM, which is better than a drop of about 400RPM when the AC is on. I have it set for 800RPM idle with no AC and 1000RPM with the AC on. I would like a few more thousand RPM when the AC is on, but oh well it works.