Vermonster00

My 2000 Cherokee has finally started to have electrical issues. Currently, my blower does not work for heat and AC. This happened today. Not good in a northeast winter. My AC has never been cold but that's besides the issue. Also, my rear wiper stopped working around the same time the blower quit yesterday. A few weeks ago my radio would not turn on all day and then it magically came back on. My LED light bar also decides when it wants to randomly not work. Depends on the day I guess. That could be unrelated since it's a cheap eBay bar. Also, when I went through the car wash a week ago, my battery gauge wasn't working but came back on within minutes. My main concern is the blower. The fuse is fine. Speed setting #3 never worked, only 1, 2, and 4, now nothing. This sounds like a grounding issue or something because of all the other small issues. I really appreciate the feedback, so I do not go wasting my time without first getting the expert opinions!

Redfire585

Check your blower resistor or the relay, both of which are located under the glove box, mine went out late last year and that was my problem.

BlueRidgeMark

Grounds are always a good place to start, but blowers? That's very often the blower resistor. Not expensive. Do a search on Youtube for how to replace it.

Vermonster00

So I started digging today and this is what I found..


I cleaned this a little, believe it or not, it was worse. Looked like a mouse died in there.







I'm wondering if the plug shorted out and blew the fuse. I haven't checked the fuse yet since I'm at work but I did check continuity between the pins on the resistor and there is surely a poor connection from the corrosion. I did get them to read between 1 and 3 ohms however but I have no idea what resistance they should have. Then I saw the plug was all melted and pretty much shot. So I'm assuming I'll need a new resistor, plug and maybe a fuse. Some more info would surely help if anyone has been here. Thanks.

Vermonster00

Well I lied. I just checked the fuse and it is still good. Now I'm thinking the short in the blower motor resistor connector is shorting my other connections such as my rear wiper blade? Anyways, I guess I'll replace the resistor and connector harness.

BlueRidgeMark

Yeah, that may not be a gun, but it's smoking. Yes, replace it and see where that gets you.

moparado

Those connectors are toasted no pun intended.
Yeah as mentioned, replace them, the relay and resistor module.
And start out fresh before condemning the blower motor but keep a close eye out.

The resistor module has a safety internal thermal fuse, surprised it didn't open circuit.
The burnt connectors could also be caused by a faulty high impedance contact in the connector creating heat. Once that happens if hot enough the heat can turn plastic into carbon which can conduct current further melting the plastic.

Its also possible the blower motor is shot or clogged up with debris causing it to draw more amperage than intended. After changing out all the above hardware and still have a problem, measure the current draw from the blower motor with an amp meter.

Changing the blower motor on a 2000 is no fun with AC. Been there done that.

nujeepguy

often the heat melts connectors, the resistors are ok. hummer had a recall on the harness, same problem,conn, rarely the resistor assm

moparado

In the OP'ers case, IMO that rusted to hell resistor module needs to be replaced along with the relay. Hate to see what the relay contacts look like. They're not that expensive and a good PM practice.
The resistor coil leads are crimped on. Corrosion at the crimps can cause arcing thus creating heat related or intermittent issues...same with loose or corroded connector contacts.
Not saying this caused the melted connector.
By the pictures, 'looks' like an over current condition at the black wire. But we might never know the root cause.

Leaving the blower on the lower speed settings utilizes most or all of the resistors creating the most heat in the resistor module. Some of the resistor coils glow red hot.

Also if the motor is running at then abruptly shut off, the inductance of the motor's winding's stored electrical energy tries to keep the current flow going anyway it can from its source. One of the prime reasons relay and on/off switch contacts fail in motor circuits.

This phenomena is called an inductive arc which can reach very very high but short lived voltages across relay contacts. Voltages high enough in some cases to create carbon tracks in or around plastic connectors or degrade relay contacts. Once a carbon track in plastic its there forever.
Again not saying this is the root cause in the OPers case.

I also have a 2000 xj and went through all that with no melted or burnt connectors in the blower circuitry, just a bad relay with toasted contacts and a bad blower motor. The resistor module tested ok but replaced anyway.

Vermonster00

So I replaced the resistor and relay and nothing is working. Yesterday, when I had the resistor unplugged I turned the blower on for ****s and giggles. The high speed worked and I turned it off quickly fearing I might blow the motor somehow. Well now that I installed a new relay and a new resistor, nothing works on any speed. So I guess now I should check my blower motor to make sure that is still working? How do I get to that and check it? Also, what else should I check now that I've narrowed it down. This is getting very frustrating since tomorrow will be 5 degrees.

Vermonster00

Anybody have any insight into what it probably is and how I can check ?

moparado

Did you replace that toasted connector?

Remove the heater/ac/blower control panel under the radio and visually check for toasted connectors and wires there. Easy to remove.
Based on that toasted connector either the connectors or one of the control panel switch's could also be toasted. Not all that uncommon.

Note:
When the blower is switched to hi speed, all the resistors are by-passed by the speed switch allowing full battery voltage to the motor via the relay.
According to the Haynes schematic, it 'looks' like the hi-speed current path to the motor is through the resistor module suggesting the motor shouldn't of run with the resistor module unplugged.
But these Haynes schematics are generic and in some cases over simplified. So i can't say for sure why the motor ran with the resistors unplugged or if its normal or a short circuit somewhere.

After checking the control panel and it visually looks ok, turn the blower on medium then go under the hood and jiggle the connector at the motor and also tap the motor.
The motor connector could be bad or the motor brushes could be shot if the motor starts. If it starts, its either the motor or motor connector.
These blower motors are notorious for intermittent problems.

After all that and still an issue, then you're gonna have to get the schematic and a multi-meter and trace the entire circuit out.
I'd start by measuring the voltage at the motor connector and trace back from there.

Vermonster00

I did replace the connector that plugs into the resistor. The connectors behind the switches by the radio do not look damaged but I could barely see since I cannot pull the entire switch plate out because the wires are too short I did try wiggling the motor connector while the Jeep was on and it did nothing. It looks like I'll need to unbolt some parts to get to the motor? I'll have to check YouTube I guess because I don't know how to get to the motor.

CCKen

You said you checked the 'fuse'. Which fuse? F25 in the JB or the HVAC Blower fuse in the PDC, or both.


Here's a schematic for the blower circuit.



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The JB, showing F25.



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The PDC showing the location of the HVAC Blower fuse.



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Vermonster00

I checked Blower fuse in the PDC. I have not checked the F25 fuse.