More HeVAC Problems

96 RR 4.0se

The HeVAC Module constantly cuts the compressor on and off. I traced
the problem back to the AirCon Request and Grant signals to the BeCM.

My request goes from 12v to .6v and just constantly fluctuates when I
get over 15mph. When it goes high, it kills the compresser, when it
goes back to low, it cuts on. The HeVAC just constantly toggles
between turning it on and off.

If I accelerate or rapidly increase my RPM's, the HeVAC will keep the
AC on, but as soon as my RPM's get under 1500 rpm's, it goes back to
the oscillations.

The compresser will stay on if the RR is under 15 mph.

I have replaced the clutch, all pressure switches, and tried to verify
the output of the various sensors.

Any idea's?

davebl @ mac . com

Ok, I have a quasi-update:

I went to check the evaporater temp sensor and mine is somewhat
different from the service book's.

Instead of a long rod type deal, mine was simply clamped on one of the
pipes going to the evaporater. Is this normal or could that be a
problem?

dave




[email protected] (David Blasingame) wrote in message news:<[email protected]>...
> 96 RR 4.0se
>
> The HeVAC Module constantly cuts the compressor on and off. I traced
> the problem back to the AirCon Request and Grant signals to the BeCM.
>
> My request goes from 12v to .6v and just constantly fluctuates when I
> get over 15mph. When it goes high, it kills the compresser, when it
> goes back to low, it cuts on. The HeVAC just constantly toggles
> between turning it on and off.
>
> If I accelerate or rapidly increase my RPM's, the HeVAC will keep the
> AC on, but as soon as my RPM's get under 1500 rpm's, it goes back to
> the oscillations.
>
> The compresser will stay on if the RR is under 15 mph.
>
> I have replaced the clutch, all pressure switches, and tried to verify
> the output of the various sensors.
>
> Any idea's?
>
> davebl @ mac . com