1999 2DR Tahoe - Heater Board Burn

[heathtd]

All,

Just became a member of the Tahoe and 2 Door Tahoe club this past weekend. I've been going through it and fixing a few things and ran across some issues with the heating/AC controls.

Symptoms:
1) Fan only worked on hi
2) Burn marks on heater control board. Sodered 10 Ohm/2Watt resistor in place of original (assumed 1 Ohm resistor) - original was so burnt, couldnt tell
3) New 10 Ohm resistor started smoking when I changed the temp
4) Fan switch control plug was burned when I opened the dash.

Things I've done (outside of #2):
1) Changed the fan heater resistor
2) Changed fan switch
3) Sodering as desribed in #2 above.

Not sure what the next move should be to correct the problem. Was hoping someone on the forum experienced this or something similar and was able to fix it.

Any help is greatly appreciated.

 

[Gzes]

Sounds like theres a short have you checked for touching wires or connectors? Maybe the actual heat/ac switch is bad?

 

[heathtd]

I've changed the only switch that I could in the back. Also did not see any wires that were touching to cause a short.

Two things I recently came across:
Have done some research and have also read it could be the motorized air door inside of the AC unit. I heard it move when the temp changed.

Also read that hot water solenoid valve that controls the flow of hot coolant to the heater core.

 

[SunlitComet]

you should have changed that control board. it is possible for it to short out when something metal touches it.

 

[heathtd]

For those that may encounter this problem, it appears we may have found the main culprit.

Took off the blend door actuator. Popped the cover and the largest gear (attached to the metal drive socket) had a giant crack in it, which caused the gears to bind and the motor to draw excessive current.

Note: This gear cracked due to manufacturing issues because it is pressed onto the shaft which overtime will put stress in the gear. its replacement is a 1-piece plastic gear with hub combined.

While we have part of the dash apart, I'm going to toss in a new blower motor becuase those also encounter issues over time.

Once completed, I'd be glad to update. I appreciate everyone else posting information and solutions, so I'd thought I'd try to give back to the forum.

Off to pop tops and turn wrenches.

 

[SunlitComet]

you are the first to have issues with blend door gear crack actually. to me anyway. never heard anything like that happening before.

 

[heathtd]

It was definitely interesting. You could spin the gears and once it came to the crack it would bind up. All in all, replaced that part and then the blower motor. So far so good...fingers crossed...