Pete 387 AC cab controller

[Rawze]

(07-04-2017 )Sergiu Wrote:  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.
P.S. Happy 4th of July The land of free and brave!!!

Good info. thanks for sharing this. It looks to me form the pictures that something is drawing too much current through the controller. I would look hard at what that thing is attached to and point my finger there as well. Moisture alone will not usually cause that much current draw, there is more to that story I would think and it will burn out again.

Just my own thoughts on it, I have not seen it first hand.

If it is in fact simply poorly designed and unable to handle the current to the device it controls, then I would consider building a relay-module or other device and have that switch control low-amperage to drive the relays instead of the motor circuit directly. - Just some speculation there.