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89 Jimmy heater

Omega's Avatar
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08-15-03, 09:26 PM   #1  
89 Jimmy heater

89 GMC Jimmy S15 4x4 V6 4.3

It has a multitude of problems, but let's just start with the most annoying (in August).
The heater blows constantly regardless of temperature control setting or whether it's on defrost/heat/ac or whatever. The rotary switch seems to be ok. It appears to be missing one of the small vacuum tubes, but I can't find it. Would it have an unused hole? Similarly, the wiring harness has five receptacles but only four wires leading into it (two of which lead into the same receptacle). Should there be an extra wire somewhere?
The blower only works on high or off, but I assume this is a separate problem.
I've tried Chilton's and alldataDIY but haven't been able to find much info.
Thanks in advance.

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08-16-03, 05:16 AM   #2  
Sounds like a failed blower resistor on the blower problem.

As for only hot air, check the operation of the vent door cable from the control to the door. Move it back and forth while watching the cable and door. Make sure nothing fell down there (leaves, pencils, debris, etc).

As for the vacuum lines---time for an Alldata.com subscription. It should be included with all the wiring and vacuum diagrams they'd provide.

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