control head and blower resistor front

[Douglas Friedberg]

Resistor module shorted and always ran even with key off. Shorted SCR in the module
But now that I replaced module another problem came about. At times I have no blower at all now control head does show operation. Does this blower resistor shorting by the way system did blow 40 amp fuse in circuit in the process. Backfire and ruin the control head circuitry as well in cases??? Seems after power recycling then blower circuit comes back on again. I see no indications of blower itself being in trouble but shorting the scr and blowing the main fuse could be its indication. I just don’t like being anparts changer. Maybe amp draw test of blower draw Any thoughts. 2006 260,000 miles.
Thank you. Doug

 

[corvette744]

Yes when the wires to and or the plug melt they say its high resistance on the blower motor.I dont know the specs but i would check it.Before you recycle the head unit do you have power at the resistor and or blower.If you do then its not the head unit.

 

[Douglas Friedberg]

Yes when the wires to and or the plug melt they say its high resistance on the blower motor.I dont know the specs but i would check it.Before you recycle the head unit do you have power at the resistor and or blower.If you do then its not the head unit.

Connectors are fine. Previous owners must have changed that as it was in nice shapes.
No I didnot check for signal from head at time of not operating. Was my next step but just wanted to know wheather resistor assy can destroy head electronics.

 

[Fless]

You generally won't find amp draw specs on the blower motors, but you can measure it -- and test it for function -- directly using a 12v (fused) source. It shouldn't be more than about half of the correct fuse value for the high fan speed circuit.

I'm pretty sure that the high fan speed on these has its own fuse direct from the fusebox, since the lower speeds go through the resistor chain. So look for multiple fuses.

 

[MassHoe04]

The Jeep TJ forums were often mentioning issues with blown out blower resistor modules (on 01-06 models especially).

This may have nothing to do with Chevy issues (I am still new to GM), but worth a mention just in case there is any correlation...

It seemed a common thread among many of the people with blown resistors only used Low (#1) fan setting. Using low setting, thinking they would prolong the life of the blower, when the exact opposite might have been the case.

I was told the resistors burn out after holding back the full current constantly and the heat created resisting that current is what killed it.

I don't know if that is proven, but I never ran my manual fan on low all the time as a precaution. I had no issues on original blower motor control in my three years and that was a 2005 original.

Just out of curiosity... Are our GM people blowing resistors also people who have manual fan controls or are people with automatic HVAC controls also plagued with blower motor resistor failures?

 

[Douglas Friedberg]

Back in the day actual resistors where used in blower circuits just like a real resistor was used in spark ignition points systems starts on 12 runs on 6 Vdc. Chrysler on firer wall GM used a long resistive wire special for circuit. Most other resistors were wire wound with crimped ends generally last a life time. Mostly switches melted and connectors melted from the heat and cheap wire sizes. Today really it’s not a resistor but a so called SCR. Silicone Controlled Rectifier A voltage is applied to a gate so called and that voltage is controlled by control head that scr is ampere rated and a 2.00 cost item or less built into the so called resistor module. That scr csrries all the current to the blower and fails from heat build up. Is why they have a big heat sink attached directly to that scr and use special heat sink compound to help transfer the heat to the heat sink. Cost is the brink of failure the next size up scr is more money. God forbid save them Pennie’s. Connector failure is still showing its ugly Face can’t handle the heat cheap plastic as well. And yes as blower gets old excess bearing clearence in cage rotor starts hitting inside windings bearings lose there LUBE gets hard to turn amps go up beyond SCRs rating **** it’s gone.
On my unit blowing out main fuse 40 amps and then shorting out SCR (resistor) module gone but something also happened to control head it’s goofy now as well.
Blower just goes off as its running controls don’t respond and turning control head on/off doesn’t help. But what does make it come back on is cycling the ign switch on/off so something is fishy with circuit still that resulted from blowing 40 amp fuse. Well lights in panel are 50% gone so time for a newer updated unit I guess 160.00 new I’ve found.