HVAC System Fails to Operate in any mode

Tiny
CIP
  • MEMBER
  • 2002 BUICK RENDEZVOUS
  • 76,000 MILES
While driving the HVAC system suddenly quit while operating in cooling mode; no fan on any speed or in any vent position and the AC/Recirc lights went out. The two fuses in the passenger foot well related to HVAC operations (10A and 25A) are intact visually.
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Sunday, October 2nd, 2011 AT 3:41 PM

6 Replies

Tiny
CARADIODOC
  • EXPERT
The HVAC Computer is a high-failure item. Too bad the insane engineers turned a once simple mechanical system of levers and ****s into a Rube Goldberg system of complicated, unreliable electronics.

You can start by flexing the electrical connector on the computer just a little. If the computer turns back on and starts working, there may just be broken solder connections on the connector pins inside the module. Those can be resoldered after the covers have been removed. You can also remove and reinstall the connectors. If there's a light film of corrosion on the pins, the scratching action of sliding the connectors off and back on will create a clean shiny spot for it to work for a while.
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Sunday, October 2nd, 2011 AT 6:43 PM
Tiny
HMAC300
  • EXPERT
I'm sendign a pic of fuses in center console. They need to be physically removed and looked at tosee if they are blown. Tehre is also oa relay on the hvac unit by the blower, that may be burnt out. If not you'll have to have your control unit belwo the radio checked for operation.
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Sunday, October 2nd, 2011 AT 6:44 PM
Tiny
REBEKAHOMAS
  • MEMBER
I also had the same thing happen, but the fan selector **** was acting strange for sometime before it went out completely. The fan only worked on levels 2 and 3. What part needs to be repaired or replaced now? Also, the computer wires to wiggle around, are those in the floor console on the drivers side?
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Friday, October 7th, 2011 AT 9:55 PM
Tiny
HMAC300
  • EXPERT
The computer is the part that turns the heater on an doff
if you only have 2 speeds thenit can be what is called the resistor which is by the motor as well as the relay. The relay controls high speed
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Friday, October 7th, 2011 AT 10:06 PM
Tiny
REBEKAHOMAS
  • MEMBER
I had two speeds, now nothing. The dial from hot to cold still works, it just won't blow. Did the resistor fail completely and needs to be replaced? I noticed the price of a resistor is much cheeper than the computer heater selector switch. How will I know which of the two it is?
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Friday, October 7th, 2011 AT 10:15 PM
Tiny
HMAC300
  • EXPERT
See if the resistor is getting power or not if it'snot then your control unit is shot
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Friday, October 7th, 2011 AT 10:17 PM

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