ardakota Posted June 25, 2016 Share Posted June 25, 2016 I have an 04 mack ch model and the wiring to the heater fan switch gets hot and burns the switch out in a short period of time it only really gets real hot when you run it on high and the next notch lower it just gets a little warm. Has anyone got a fix for this. Thanks Dave Quote Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/ Share on other sites More sharing options...
41chevy Posted June 25, 2016 Share Posted June 25, 2016 IMO I'd look fora dirty/loose ground on the blower motor circuit, assuming this is a recent occurrence. Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/#findComment-337530 Share on other sites More sharing options...
turckster Posted June 26, 2016 Share Posted June 26, 2016 I'd make sure each one of the terminals in the switch connector are clean and have a good amount of drag when sliding a terminal in/out. Quote Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/#findComment-337578 Share on other sites More sharing options...
ardakota Posted June 30, 2016 Author Share Posted June 30, 2016 terminals clean and actually ran a ground in addition to the one thats factory still getting hot on high the fan is new switch is new the only thing in this ac system that hasnt been changed is the thermostat and the resistor. Im at a loss on what to do next. Quote Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/#findComment-337992 Share on other sites More sharing options...
tjc transport Posted June 30, 2016 Share Posted June 30, 2016 put an amp gauge in the circuit and see what amps it is drawing. then remove the resister from the circuit and wire motor direct to switch. i bet you will see higher amps with resister in line, telling you the resister is bad. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/#findComment-337997 Share on other sites More sharing options...
41chevy Posted June 30, 2016 Share Posted June 30, 2016 1 minute ago, tjc transport said: put an amp gauge in the circuit and see what amps it is drawing. then remove the resister from the circuit and wire motor direct to switch. i bet you will see higher amps with resister in line, telling you the resister is bad. Ya beat me as I was typing that.. Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/#findComment-337998 Share on other sites More sharing options...
mrgumby Posted July 1, 2016 Share Posted July 1, 2016 (edited) where did you put the ground? try runnin a temporary ground directly to the battery ..you may have a band ground in the cab and maybe creating a ground loop..check all grounds to cab..seen bad grounds cause many hot wires Edited July 1, 2016 by mrgumby Quote Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/#findComment-338002 Share on other sites More sharing options...
MHfred Posted July 1, 2016 Share Posted July 1, 2016 I would replace the wire that is getting hot. Make sure you have good connections on both ends. Quote Link to comment https://www.bigmacktrucks.com/topic/45785-04-mack-heater-fan-switch-wiring-getting-hot/#findComment-338014 Share on other sites More sharing options...
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