Pete 387 AC cab controller

[Sergiu]

I don't know where to start.. thing is that I'm still searching for the reason of my AC problems, the blower motor runs on 2nd speed continuously even I've changed the thermo-resistor, blower motor, thermostat and have put in a new speed switch (bought it from grainger for 10$) and just soldered the wires to it.
I'd like to share my discoveries. AC controller module is not a cheap part on these trucks got two of them blown in one year. Please see attached pictures. I think the reasons are moisture and cheap parts used in this controller. So my advice when you put in a new one, take it apart and spray it with silicone spray or dielectric grease only between contacts. The distance between them is so small that a small condensation on one contact can easily reach it's neighbor and now your blower runs at two speeds at the same time.