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bad heater control unit??

I

Irbys19

NAXJA Forum User
Location
Murfreesboro TN
I pulled the heater control unit out today thinking i had a possible vacuum leak and much to my amazement i still had vacuum to the heater control unit, BUT it is not sending out any vacuum to anything else that it should. So my thoughts are This must be a bad unit right???? And the pics below show the connectors on the back of it. I guess it shorted out the unit even though it still will power on but only in the high position
jeep1.jpg

jeep.jpg
 
With a vacuum diagram and a piece of vacuum hose you could bypass the controls to see if the actuators/doors work. The melting/hot switch and connector could be a poor connection at the switch (loose terminals), bad switch, or blower motor that's drawing too much current.
 
I found that my wiring harness was brittle and melty, and not salvageable, so I bought a 35 amp 2 position toggle, and a fuse and some butt connectors but I need a diagram to know which spade is which on the back of the old switch so I can wire up 2 speeds. also does anyone think it will be a problem if i wire up one to high and one to m1? low doesnt do much anyways and m2 isnt much different than high. Or should I leave high off and use m1 and m2 instead. I just need a pic identifying the spade connectors if anyone knows what I mean.
 
gushaman said:
I found that my wiring harness was brittle and melty, and not salvageable, so I bought a 35 amp 2 position toggle, and a fuse and some butt connectors but I need a diagram to know which spade is which on the back of the old switch so I can wire up 2 speeds. also does anyone think it will be a problem if i wire up one to high and one to m1? low doesnt do much anyways and m2 isnt much different than high. Or should I leave high off and use m1 and m2 instead. I just need a pic identifying the spade connectors if anyone knows what I mean.
Click to expand...

Keep one wired up to high, because that bypasses the resistor completely. Resistor burns out (not uncommon), you still get blower.

For wiring help, you need the MODEL YEAR for sure.
 
MJR said:
With a vacuum diagram and a piece of vacuum hose you could bypass the controls to see if the actuators/doors work. The melting/hot switch and connector could be a poor connection at the switch (loose terminals), bad switch, or blower motor that's drawing too much current.
Click to expand...

Blower only works on high is usually resistor burnt out. You can check that out with your ohmeter. Your motor is likely drawing too much current too. So you probably need motor, resistor and switch.
 
winterbeater said:
You didn't tell me this before I bought my XJ. I should have just put Dana 60's on my CrownVic.

:sure:
Click to expand...

D60s on a Crown Vic--I like it! party1:
 
winterbeater said:
Keep one wired up to high, because that bypasses the resistor completely. Resistor burns out (not uncommon), you still get blower.

For wiring help, you need the MODEL YEAR for sure.
Click to expand...

My bad its a 95 se 4 cyl part time. I have the chilton SUCKS i just need to know which is high and which is m1 or m2, mine looks like the pick at the top of this thread.
 
I am becoming a pro at replacing the resistors.

Had one go this morning, had 2 spares. Popped old one out, looked at it looked normal but was only working on high fan. Maybe resistor blew internally, i dont know.

The reason it went was because I was extending wires on back of stereo. No big deal.
 
The resistor can look fine, but the thermal fuse melts inside. You can solder in a new one from radio shack to save the resistor if the coils look OK. Check with an ohmeter and you will see the fuse has melted, and you can verify that the coils are really still good.
 
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