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No Heat, fan only on high, no mode select. 95 Silverado
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Normk1
Novice
Jan 24, 2009, 7:42 PM
Post #1 of 8
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No Heat, fan only on high, no mode select. 95 Silverado
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Hi
I just bought a 1995 Chevy Silverado Ext cab 2wd. 5.7l V8. Auto trans.
Odometer says 194k. Engine and tranny work great as do most all other things, except the A/C and heater controls....
Here are my problems.
1) No heat.
2) Fan only blows in high.
3) Mode select is intermittent and sometimes not at all.
Actions taken on problem #1: (No heat or hot air)
Changed thermostat. Old one was stuck open. Gauge goes up to about 190 now. before it would not. No vacuum valves located under hood. Both sides of heater hoses feel hot as if coolant is flowing. Suspect temperature door motor, but have yet to locate it.
I still have no heat.
Actions taken on problem #2: (fan or blower only blows on HI)
Replaced blower speed switch. Still no blower except on HI. Tested switch with ohm meter and it checks good. Bought blower resistor. I have not located or replaced it yet.
I still have fan only on HI.
Actions taken on problem #3: (no or partial mode control)
Seems to be stuck primarily in the defrost mode, but have occasionally gotten air from the heater or floor vents. Suspect the mode door motor, but have not located it.
I still have improper mode control.
Has anyone run into these problems before? Any help would be greatly appreciated.
Thanks.
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zmame
Veteran
/ Moderator
Jan 24, 2009, 9:48 PM
Post #2 of 8
(11303 views)
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Re: No Heat, fan only on high, no mode select. 95 Silverado
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blower motor resistor is located back of the glove compartment, once you remove the glove compartment you will see it right back of the three connector.
Not to sure about your heat selection switch, but if it's stuck on defrost then you have a vacuum leak.. if its like the fords they run selector door runs off vacuum they they would leak there the lines go through the firewall and since there no vac cause it to go back to defrost.. im not sure if heater door runs off vac or not on chevs someone here should know.
I would listen and try to find vac leak maybe kill 2 birds with 1 stone
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 25, 2009, 12:46 AM
Post #3 of 8
(11301 views)
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Re: No Heat, fan only on high, no mode select. 95 Silverado
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Pretty sure actuators are all electric. It's curious that all three knobs have a fault at the same time, selection, temp, and fan speed. Resistor is behind glove box as said on top of blower + distrubution box.
Has dash been removed or any work done lately that could have left things disconnnected in this? That's three faults if I'm reading this right.
Actuator for "defrost, panel, mix and floor" is over gas pedal but if this has airbags and remote locks is behind a plate to really see it work. Rods have cheap plastic clips and springs that come undone if disturbed and you might see them just swinging around or not moving at all with requests. Two rods leave that one actuator,
T
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Normk1
Novice
Jan 25, 2009, 5:42 AM
Post #4 of 8
(11292 views)
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Re: No Heat, fan only on high, no mode select. 95 Silverado
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Thank you very much for the hints, suggestions and where to look.
I am about to go out there an start looking. My truck has electric controls for these things. I do not belive vacuum is involved.
Thanks again and I will post what I find.
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Normk1
Novice
Jan 25, 2009, 5:47 AM
Post #5 of 8
(11288 views)
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Re: No Heat, fan only on high, no mode select. 95 Silverado
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Pretty sure actuators are all electric. It's curious that all three knobs have a fault at the same time, selection, temp, and fan speed. Resistor is behind glove box as said on top of blower + distrubution box.
Has dash been removed or any work done lately that could have left things disconnnected in this? That's three faults if I'm reading this right.
Actuator for "defrost, panel, mix and floor" is over gas pedal but if this has airbags and remote locks is behind a plate to really see it work. Rods have cheap plastic clips and springs that come undone if disturbed and you might see them just swinging around or not moving at all with requests. Two rods leave that one actuator,
You bring up an interesting point about all three having problems. I am going to check some fuses. Than check power supply to control circuit board. Thanks. As far as dash being removed, not that I know of. I rather doubt it. Truck has airbag in steering wheel, but not over glove box. The locations for these things and what they look like are a big help. I am about to go outside and start checking things. I will let you know what I find. Thanks a million! Norm
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Normk1
Novice
Jan 25, 2009, 8:00 AM
Post #6 of 8
(11282 views)
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Re: No Heat, fan only on high, no mode select. 95 Silverado
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PROBLEMS FOUND AND SOLVED!
I will start with the fans speed problem, as I fixed it first...
On top of the housing for the evaporator core, heater core and blower motor it an assmbley with 4 or 5 wire resistors and a thermal fuse. The resitors for of various values to ger different fan speeds. They mount in the air box for cooling. The thermal fuse was open. I replaced the assembly and restored proper blower operation. It was hard to get the old blower resistor assembly in and out, but it can be done without taking the dash apart. You will need to remove the glove box to get to it.
On the no heat or hot air issue. It turned out to be a wire was off or unplugged from the PC board that the controls for the temperature and mode selection are mounted. I re-connected this wire and proper operation was restored.
Now, I am going to have to replace the assembly because the plastic that holds everything together is very brittle and has pretty much fallen apart.
Any good sources for these besides Chevy dealer. They are over $200 there...
Thanks again for all the help!
Norm
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 25, 2009, 8:49 AM
Post #7 of 8
(11281 views)
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Re: No Heat, fan only on high, no mode select. 95 Silverado
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Sounds great so far:
Re: The broken plastic assy: What exactly broke and do you have all the peices? It might be glueable with the right products and tricks,
T
Ps: Finding something unplugged DOES suggest something has been done it there before....
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