Good morning folks,

I picked up my Cherokee about a month ago now, and after a couple weeks actually got it running reasonably well.

Well, as I have been getting things together on it I have been amking a list of broken things as I find them. Yesterdays project was a blower motor that was not working.

Not an "I only have high speed" issue like I had with my Comanche, which turned out to be the resistor. But not working at all.

Since the switch in the dash was froze in one place I figured that was a good place to start looking.

Anyhow, once I got the dash apart I found the selector switch was scorched and melted. I removed it, and checked the wires for power. Yep, it was there, right where it should have been.

Decided to check to see if I could just wire around the selector switch to get high speed only, managed to get nothing from the motor. (was hoping to have at least high for defrosters till the weekend)

What it boils down to is I know my switch is shot, as is the connector that went to it. (everything is now rubber taped under the dash and turned off to prevent further damage). Both will be getting replaced as soon as I make it to the JY to get parts, probably this weekend.

In addition I am pretty sure my blower motor is shot, though I may have tested it improperly.

I was thinking of replacing both the motor and the resistor at the same time I do the switch.

My questions are:

Is there a better way to test the motor itself?
Is there a way to test the resistor?
Is there something else I may be overlooking?

Thanks,
Brad

 

One thing to look at is why the switch melted and didnt blow the fuse. Sounds like PO had a problem with the blower blowing fuses and just put a larger fuse in it (too large). Just my $.02. If it were me I would go ahead like planned just replace everything.

 

Don't count on finding a switch at the junkyard ... all the ones I found were melted as well.


More likely this is the scenario ...

First you have to understand how the switch is constructed. The terminal lugs are RIVETED on the back of the switch.

Every bad switch I looked at had LOOSE RIVETS , this makes for a poor electrical connection.

The connection is weak and over time it will heat up, the effect of the heat is cumulative over time even though the circuit is below the current threshold to blow the fuse it will still heat up.

I've looked at the switches of over 14 jeeps XJ's in junk yards and always found those rivets to be loose.

My entire life has been spent working in electronics and that experience has led me to the conclusion that either .....
1) Poor switch design. ( I wonder if soldering the rivet to the terminal lug on the back of the switch might help prolong their life )
OR
2) Stress on the switch from an improperly secured wiring harness
... is what leads to the failure of the switch without blowing a fuse. ( or a combination of the two )

Not saying that a PO did not up the fuse, because he could have but I have seen enough melted connectors on those switches and the vehicles had the proper fuse.

Because of this, both of my XJ;s got BRAND NEW switches within a month of purchase. Spare switches are in hand as well, and you can be sure I will be checking those switched regularly.

 

Motor test - should be able to disconnect fan, and apply 12VDC to it to test operation.

Resistor Test - remove it and do a visual inspection - it is a open wire wound resistor and if bad you will see breaks in the coiled wire.

Overlooking anything else?

I don't think so ..... switch - resistor - motor .... make up the entire system except for wiring harness and connectors.

 

Alrighty, I had some time to check it out yesterday.

Pulled the motor, it checks out fine. Awesome, $28 I don't have to spend.

The resistor looked fine, but for $6 I just tossed a new one at it.

Pulled the remains of the switch out and replaced.

That leaves me with one issue before I can test it, the plastic housing for the wires was damaged and cracked away. The wires and the female connectors appear fine, I simply have no reference to which blade on the switch each one should be plugged in to.

Anyone have a picture of the back of thier switch, or of the pigtail that goes to it, so that I can tell what goes where by color code?

 

If you can find someone with a 1995 Factory Service Manual the wiring diagram for the Heat/AC fan is in there.

It is wiring diagram 8W - 42 - 3

 

I found someone with a copy of the '94 FSM and got the pinout info from that.

It's all back together now and working for the time being.

I will still be buying that pigtail next time at the JY to fix it right, but heat shrinking the female connectors and plugging them into the switch is working for now.