Instrument cluster gauges not working. on 1998 Dodge Caravan

I changed a faulty heater control module (the controls under the radio), and when I plug that in, my gauges quit working. They work fine if I leave the wiring unplugged on the heater controls.I left the controls on heat and defrost and I do have the fan control plugged in for defrosting and heat for cold mornings. But doing so, I do not have control over temperature or control for rear window functions now (defrost, wipers, etc). Could problem be in wiring itself or with the cluster, or perhaps the used heater control module I put in. The self diagnostic on the heater control module ends up with no fault codes, but with the heater control wiring plugged in, I cant even get the self dianostic on the cluster to activate until I unplug it from the back of the heater control.

by in Brooklyn, NY on October 13, 2012
1 answer 1 comment
ANSWER by on October 13, 2012
used unit??? first mistake. you should always use new on these electronics. was the cluster working ok with the bad module?? Roy
COMMENT by on October 13, 2012
Both the cluster gauges and heater control module were giving me problems. The module finally quit. I noticed today while driving (I still have the heater module wire harness unplugged) that the gauges quit and when I thumped the top of the dash, they came back on. I may have more than one problem here. Also, the plastic plug end of the wiring harness that goes into the heater module has some signs of excessive heat or shorting. The plastic is slightly melted and dark at the left pin holes (when looking at it from the driver's seat). Thinking I will try to change the harness and repair any cluster solder joints that look bad.
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