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Posted: 1/23/2009 10:59:45 AM EDT
So I am out in the mountains of Colorado on an elk hunt and my heater stops working.  I narrow the problem down to the switch and say I will fix it when I get back home.

Here is what I find when I pull the dash off later.



It completely melted the plastic connector and wires.  Fried the back of the dash panel as well.

Any suggestions?  Any ideas how this happened?

Update:

I spent a couple more hours researching this and found this thread at jeepforum.com

It seems Chrysler used wire too small to handle the load when the motor starts to wear out and increase the amp draw.  A lack of relays in the circuit further compunds the issue and has led to vehicle fires.  Way to go, Chrysler.

It explains everything.  Thanks for the help guys, I am going to rewire the entire thing with larger wire.
Link Posted: 1/23/2009 11:14:19 AM EDT
You won't find one in a junkyard.

That's a very common problem, my buddy's switch was burnt up on his trail rig and when we went to the yard, all 4 of the cherokees we pulled had the same switch burnt up.

Couldn't tell you how to fix it, try looking at JeepForum that's where he found an answer.
Link Posted: 1/23/2009 11:24:58 AM EDT
Wow, I hate to hear that it is common.

Thanks for the reply.

Poor Cherokee is turning into a money pit.
Link Posted: 1/23/2009 11:27:18 AM EDT
Quoted:
Wow, I hate to hear that it is common.

Thanks for the reply.

Poor Cherokee is turning into a money pit.


Possibly blower motor drawing too many amps - let me check Identifix for you real quick. brb
Link Posted: 1/23/2009 11:28:05 AM EDT
Quoted:
Quoted:
Wow, I hate to hear that it is common.

Thanks for the reply.

Poor Cherokee is turning into a money pit.


Possibly blower motor drawing too many amps - let me check Identifix for you real quick. brb


Oh yeah - I need year, engine, and is it a Cherokee or Grand Cherokee?
Link Posted: 1/23/2009 11:41:27 AM EDT
'94 cherokee sport .  Inline 6.
Link Posted: 1/23/2009 12:00:34 PM EDT
Quoted:
'94 cherokee sport .  Inline 6.


OK disregard the fact that this is a 96 model, as it is still the same as your system.  The problem appears to be from a defective switch and associated ground.  This repair trac I'm posting gives you wire colors to trace to check the ground - check with Jeep about the switch connector.

1996 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6  

Mileage: Unknown

Customer Concern:
Blower motor is inoperative.


Tests/Procedures:
1. Check for a ground on the Dark Green wire at the A/C controller. The Dark Green wire changes wire color at the C206 connector, becomes a Black wire, that goes to the C160 connector near the blower motor.

2. If the Black wire is grounded at the C160 connector but not at the C206 connector, find and repair the open or run a new wire.


Potential Causes:
Wiring

** Confirmed Fix **
Wiring melted behind the heater control panel


Tech Tips:
The blower switch controls the ground side of the blower motor.


Diagnostic Codes:
None
Link Posted: 1/23/2009 12:04:44 PM EDT
Quoted:
Quoted:
'94 cherokee sport .  Inline 6.


OK disregard the fact that this is a 96 model, as it is still the same as your system.  The problem appears to be from a defective switch and associated ground.  This repair trac I'm posting gives you wire colors to trace to check the ground - check with Jeep about the switch connector.

1996 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6  

Mileage: Unknown

Customer Concern:
Blower motor is inoperative.


Tests/Procedures:
1. Check for a ground on the Dark Green wire at the A/C controller. The Dark Green wire changes wire color at the C206 connector, becomes a Black wire, that goes to the C160 connector near the blower motor.

2. If the Black wire is grounded at the C160 connector but not at the C206 connector, find and repair the open or run a new wire.


Potential Causes:
Wiring

** Confirmed Fix **
Wiring melted behind the heater control panel


Tech Tips:
The blower switch controls the ground side of the blower motor.


Diagnostic Codes:
None


Awesome, thanks a bunch.  I am going to go check the ground and will write up the results later.
Link Posted: 1/23/2009 12:06:39 PM EDT
Good luck Sapper - that repair trac didn't reveal any ground breaking new to you, but it does indicate that you likely don't need to invest in a blower motor as well as the burned switch & connector.  LMK if I can be of any more help to you.
Link Posted: 1/23/2009 12:07:21 PM EDT
Not sure if it's the same issue, I had a 98 TJ for about 10 years.
The resistor module (unit, thingy, etc.) for the blower motor would burn out all the settings except for full blast (which had no resistor).
They put the damn thing in vent under the glove box.  So leaves, moisture and other crap would get filtered down there from the fresh air intake and just sort of rots on top of it.  I had several of those replaced while it was under warranty, then just learned to live with full blast or off until I went to sell the Jeep and I replaced it.
Link Posted: 1/23/2009 12:09:04 PM EDT
Quoted:
Not sure if it's the same issue, I had a 98 TJ for about 10 years.
The resistor module (unit, thingy, etc.) for the blower motor would burn out all the settings except for full blast (which had no resistor).
They put the damn thing in vent under the glove box.  So leaves, moisture and other crap would get filtered down there from the fresh air intake and just sort of rots on top of it.  I had several of those replaced while it was under warranty, then just learned to live with full blast or off until I went to sell the Jeep and I replaced it.


Yeah - we sell a LOT of blower motor resistors - but the OP has an issue in another area of the same circuit.
Link Posted: 1/23/2009 6:13:44 PM EDT
They put the resistors in there to help cool them....they run pretty hot......
Link Posted: 1/24/2009 6:20:33 AM EDT
I have the same issue on my 2000 Jeep Wrangler. I've replaced 2 switches. Guess I need to rewire too.
Link Posted: 1/31/2009 10:44:38 AM EDT
Quoted:
They put the resistors in there to help cool them....they run pretty hot......


No - the blower motor resistor controls the fan speed.
Link Posted: 2/1/2009 3:51:59 PM EDT
My 2000 Wrangler has a similar problem, but it's the connector at the blower motor resistor that's melted. When I fix it I'm going to run the wires from the switch to relays (at least for the 2 highest speeds), which will then let battery voltage through to the resistor and take the load off the switch & its pigtail. It'll probably be overkill but electrical fires ain't no joke.
Link Posted: 2/14/2009 11:53:26 PM EDT
Quoted:
My 2000 Wrangler has a similar problem, but it's the connector at the blower motor resistor that's melted. When I fix it I'm going to run the wires from the switch to relays (at least for the 2 highest speeds), which will then let battery voltage through to the resistor and take the load off the switch & its pigtail. It'll probably be overkill but electrical fires ain't no joke.


Since the melting happened at your resistor, it might have messed the resistor up.

If your fan only works on the high setting, than the thermal fuse on the blower resistor is blown.  Instead of spending $40 for a new resistor, you can go to Radioshack and buy a 128c thermal protection fuse, cut the old one off the resistor, and solder the new one on.  That way you can save $38.  There is a guide on jeepforum.  Anyone needs the link can IM me.
Link Posted: 2/15/2009 12:17:44 AM EDT
Quoted:


Since the melting happened at your resistor, it might have messed the resistor up.

If your fan only works on the high setting, than the thermal fuse on the blower resistor is blown.  Instead of spending $40 for a new resistor, you can go to Radioshack and buy a 128c thermal protection fuse, cut the old one off the resistor, and solder the new one on.  That way you can save $38.  There is a guide on jeepforum.  Anyone needs the link can IM me.



I needed a new resistor anyway, because the pins actually melted down to the flange on the resistor. The plug itself is melted so hopefully I can either find the parts to repair it at the dealer or get a good pigtail from a salvage yard.
Link Posted: 2/15/2009 9:43:27 AM EDT
OK, I found the link.

thermal fuse

Save some $$
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