heater motor wiil not shut off

[nobbs]

First post. 04 silverado 2500HD w/climate control. Its been a cold winter. Of course this happened just out of warranty. The heater motor stays on all the time, with ignition off . I am able to adjust the temp, but not the speed. the only way to turn on or shut off the blower is to pull the fuse under the hood. Any insight on this would be appreciated.

[jveik]

so i take it that when the ignition is on, the fan is designed to run all the time? if so, there must be a solenoid or some type of device that cuts the power to the fan when the ignition is turned off, and it is malfunctioning.

other than that, if it has a fan speed swich with an "off" option, there could be a short which would explain why the fan speed cannot be adjusted, basically the short is bypassing the fan speed selector switch in your dash and the fan is running as fast as the current of the short wants it to run... and i reckon that the fuse doesnt blow because the short isn't supplying enough current to blow the fuse? that's my two cents... i will hopefully know a lot more in a couple years when im in the IBEW apprenticeship and electricity will be my carreer lol so if you still have the problem then, i can help a little better than now :-)

[MT-2500]

Check for a stuck relay or the fan control module.
Also check the body/heater computer for codes.
MT

[nobbs]

thanks for the info guys. Yea, I really dont get it. It acts like a short, but doesnt pop the fuse. Yes, there is a separate off switch. Does this even have a resister card with the digital fan speed control? I will start on this this weekend

[MT-2500]

Originally Posted by nobbs

thanks for the info guys. Yea, I really dont get it. It acts like a short, but doesnt pop the fuse. Yes, there is a separate off switch. Does this even have a resister card with the digital fan speed control? I will start on this this weekend

The fan and fan speed is controled by the HVAC control module.
You really need a HVAC/body capable scanner to do any testing on it.
The fan speed is controlled by a digital signal from the module.
You will need a lab scope to read a digital signal.
I would check and look for codes past and present.
Also will the fan stop if you pull HAVC fuse 1.
The fuse should have no power with key off.
If the fuse has no power key off and fan keeps running the problem may be a HAVC control module.
If any codes post back codes.

For more info on testing and how the system works and a wiring diagram and repair flow charts.
I would suggest a all data online sub.
http://www.alldata.com/products/diy/index.html

Good Luck and
Let us know how it goes.
MT

[redlinefidelity9]

i second the above.. ive seen a small handful of failed hvac modules between 99 and 05 trucks come in the shop.
chris

[nobbs]

Its been a while, but I thought I'd post the results while I'm thinking of it for others. Yes it did turn out to be the hvac control module. Its down under the dash on the passenger side. The chev dealer wanted like $130 for the part. Bought it online for half that. 15 minute install.

[MT-2500]

Originally Posted by nobbs

Its been a while, but I thought I'd post the results while I'm thinking of it for others. Yes it did turn out to be the hvac control module. Its down under the dash on the passenger side. The chev dealer wanted like $130 for the part. Bought it online for half that. 15 minute install.

Yes it has been year and half.
How did you figure it out?
Thanks for posting back how it went.
GOOD lUCK

[nobbs]

MT-2500. After checking all the usual "easy" suspects, it came down to either the control module, grounding problem, or a short in the wiring. I took the easy route and threw a part at it. Fortunate for me it was the correct decision.

[MT-2500]

Originally Posted by nobbs

MT-2500. After checking all the usual "easy" suspects, it came down to either the control module, grounding problem, or a short in the wiring. I took the easy route and threw a part at it. Fortunate for me it was the correct decision.

Thanks for the info and fix.

[semisendiz]

Would this module (Resistor assembly-blower motor, p/n/ 15305077) be to blame as well for my blower motor NOT working on speeds 1 through 4, but works fine at speed #5...?
Does shut down when in "OFF" position....

[j cAT]

Originally Posted by semisendiz

Would this module be to blame as well for my blower motor NOT working on speeds 1 through 4, but works fine at speed #5...?
Does shut down when in "OFF" position....

If you have the MANUAL CONTROL HVAC this issue is the resistor assembly...these defective fan resistors always fail..new can be had at auto store for around 25.oo ....


the other forum member had the auto hvac system this is most always the cause for the fan to never shut down...another GM defective part ...

[semisendiz]

By manual control, you mean manual fan speed selector knob?
Would oreily's/checker/etc. Have them...?
I HAVE ORIGINAL P/N 15305077, CALLED DEALER AND THEY GAVE ME NEW P/N 89019089....

[j cAT]

Originally Posted by semisendiz

By manual control, you mean manual fan speed selector knob?
Would oreily's/checker/etc. Have them...?
I HAVE ORIGINAL P/N 15305077, CALLED DEALER AND THEY GAVE ME NEW P/N 89019089....

manual means you adjust the speed by turning the fan speed knob....not auto where the computer turns the fans on ..

most auto part stores have these .,,,since they are a defective componet they sell lots of them ! these aftermarket replacements appear more reliable ..good luck easy to replace behind glove box next to the blower motor..

[semisendiz]

Yes, thanks a mill....