Cherokee_Mike

I recently fitted the upgraded resistor unit in my 2000 WJ - chilly morning today so turned the heat up to HIGH but even with the engine hot it is just blowing cool air
The upgraded unit has a heatsink which is about 5 times the size of the old one - does the system need to be recalibrated or reset and if so, how do you do it ?
Or do I have to get one of the old style units which lasts only around a year ?
I removed the fan to check for debris etc... and it spun fine by turning it by hand so I don't think excess current draw is the problem, just a poor design on the connector - which keeps melting
Anyone else had this problem ?

dave1123

Okay. melting of the connector is a sure sign of excess current draw.

Your cold air, to me, says the heater core is plugged or your heater doors are not functioning. (stuck on A/C positioning) Jeeps have a "full-flow" heating system in that coolant flows thru the core at all times. As you know, jeeps have a blend door problem. Backpressure from a malfunctioning door can cause excessive current draw as well.

My WJ's blend door still functions, but it doesn't seal well so I get heat drifting out from it even in the summer! AND, of course, the A/C doesn't work. I have to do a leak dye check of the A/C unit to know if I have to replace the evaporator before I rip the dash apart to fix it. If I do, then I'll fix the heater door as well.

Cherokee_Mike

It was all working fine before the old resistor pack stopped working so I don't think the heater core or blend doors are the problem.


I might just get a used standard type resistor unit & swap it back in to see if that improves things.


My feeling is that with the larger heatsink the airflow is overcooling it and giving the sensors a false temperature reading ???

dave1123

I don't think so, but go ahead. We don't know nothing.

Cherokee_Mike

Update : Now resolved.


It was a broken blend door causing the problem.
Cut a hole in the heater box with a fine tipped soldering iron & got hold of a blend door repair kit - now all working fine with no fault codes showing.