"dprkk" > wrote in message
ps.com...
> After living with lukewarm heater performance for too long with my 91
> GC, I decided to get to the bottom of the problem. I found no vacuum
> to the heater core control valve. The vacuum line goes into the
> firewall to the under side of the dash somewhere. What is the
> suggested way to start troubleshooting and taking things apart under
> the dash? TIA.
>

With a 15 year old vehicle you might consider bypass rather than
repair. For little money you could run a vacuum line from manifold
to a vacuum valve you just mount under the dash and manually
operate. Run a line from the valve to the heater core control valve.

Taking the dash apart is a very complex operation. The first step
is getting the factory service manual and studying the procedures.

Ted