Automatic Tempature Control (ATC)

[dwyczalek]

I have a 1987 Mrecury GM with the 5.0 liter engine I took it to a mechanic today to see if he could find a vacuum leak he couldn't find it he said he would have remove intire instrument panel to find it, maybe somebody here might know an easier way to find it.

What it does is when you are on an incline or under load the A/C switches over to heat on level ground or not under load works fine. Does anyone know where a good place to start would be without removing IP I have already replace the ATC control (blue in color above the glove box approx. $70.00) and (also replaced the ATC servo also behind the glove box approx. $100.00)
Any help would be a great help.