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94 chevy truck blower fan speed problem


rajung's Avatar
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01-04-04, 05:41 PM   #1  
94 chevy truck blower fan speed problem

I have a 94 chevrolet silverado 4 wheel drive truck that has a defroster fan speed problem when cold.
Whenever the outside temp gets to around 30deg. or so the the defroster fan speed cannot be adjusted from where it was when vehicle was shut off the night before.
The settings still work such as defrost,lower floor area or dash vents.
The off button will not work nor the low , medium or high selections.
Once the truck is driven for awhile and inside temp raises a little(not sure how much) but usually around 5 minutes the buttons again seem to work fine.
Never have this problem when the temp outside is warmer.
I can tell when everything works normal that there must be a set of relays behinde the glove box area due to the clicking sound.
Thanks to anyone with ideas and help.

 
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01-04-04, 07:03 PM   #2  
Based on what you have described it could be a sticky relay due to the cold. Check the relay.
Hope this is helpful to ya,
Billy

 
rajung's Avatar
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01-06-04, 02:19 PM   #3  
I have all the 4 relays behinde glove box out and laying in yard-20 deg below zero w/wchill.
Hope its cold enough!
Tried blower speeds and they do not work,although the indicators still show the different levels of speed at which they should be at when clicking the adjustment buttons so I think these may not be the problem since when the blower doesnt change speed as posted above the indicaters do not change also,just stays were it was last set on.
Starting to think it may be the whole control pad behinde buttons.
Any suggestions from here?
Thanks again.

 
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01-06-04, 02:27 PM   #4  
Do you have power at the blower motor on the affected positions when it's cold out?

 
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01-06-04, 04:44 PM   #5  
yes.
If I shut the truck off for awhile and restart or just turn ignition to run position the fan /blower will run at the last setting it was at ,not good on a cold day.
The button that operates the location such as defrost,vent or floor area still works and it does change settings but the speed and off do not.
Do you know if the 3 buttuns that change this-L-M-h or off are like vcr remote or telephone buttons?
They feel the same as in spongy (normal) not a hard click like a on off switch ,I know that those type of buttons( a large pad with molded buttons) have something like a carbon/rubber or some material that seem to get greasy easy and dont like to work sometimes.
All in all not a do or die situation but its the only thing that doesnt work or look like it should so its bugging me now.
Thank you.

 
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01-06-04, 05:38 PM   #6  
The problem almost has to be in the switch/hvac control head I believe it's one piece but it's been a while.

 
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01-10-04, 05:42 AM   #7  
Well I think I have it done.
I remove the control unit,took it apart and slide out the circuit board,all one piece except for the actual buttons you push.
The touch pads are the rubber contact types and it is one piece with a plastic cover melted in place over them.
Used a fine thin knife( my Wife always thanks me for this)to pry away a little and spray some circuit board cleaner on them and the rest of the board.
Seems to work fine now for 3 days.
Just hope the buttons / pads dont swell like eggs now.
Thanks for all your replys.

 
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