Question about 1993 Buick Roadmaster

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HVAC performs normally until the car begins to move forward

1993 Buick Roadmaster with automatic HVAC system. System works fine with engine idling and car not moving. When the car begins moving in normal traffic the HVAC controls become inoperative, disabling the compressor, and will not accept manual input at the control unit on the dash. When the car is stopped,.such as at a traffic light, the HVAC controls again function normally, accepting manual inputs and permitting the compressor to operate. As soon as the car begins to move forward the HVAC disengages the compressor and refuses to accept manual inputs. All sensors are functioning per specifications. Help! This one has stumped everyone.

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  • rsimpson38 Feb 13, 2009

    Vacuum actuators are used to open and close the air valves in the air distribution duct, but everything else is electronic. I have narrowed the problem to an intermittend electrical connection but am unable to determine if it is in the wiring or in the dash-mounted control unit.

  • Mike Butler
    Mike Butler May 11, 2010

    I haven't got reference material in front of me, but obviously you've confirmed that there is no part of that system that uses vacuum correct?



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Not roadmaster but should be quite similar, if not same. (schematics) just in case this helps.

Posted on Feb 13, 2009


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I hate to be the bearer of bad tidings, BUT... it\'s obvious that these corrections you\'ve made [lots of $$$$$] have nothing to do with your problem.

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