Blower Motor Speed Issues

Still having an issue with the a/c blower on my '93 XJ. When I flip it on to high (at startup), it will only run at high for about 15 seconds, then it kicks down to medium speed on its own. Sometimes it will surge back and forth from medium to high (a "wah, wah, wah" noise). The blower switch was just replaced with no change at all, the blower motor is only about two months old, and I can't see how the resistor pack would be involved (or could it?).
The symptoms seem like some type of electrical connection getting hot or a relay getting weak and not passing full current? Any ideas on where to look next? Thanks in advance, 'cause it's HOT down here in Texas!

Well (a very deep subject for my shallow mind), if the resistor pack was failing it should default to high.

Could it be something with the air doors--possibly a vacuum source or door vacuum motor or are you certain its the motor's speed?

The HVAC switch connectors like to melt. Pull it and take a look at the back side.

Good luck.

Some of my thoughts exactly. The connector to the fan speed switch was a little toasty, but I tightened the actual spade connectors inside (the platic plug is just a shell that holds female spades). The blower motor is only two months old, and when I checked the fresh air recirc door for opening/closing (right floorboard under the dash), I put my ear down and could definitely hear the fan slow down from H to M. THAT is the real mystery, the fan SLOWING DOWN instead of defaulting to High. I'm headed out right now to pull the resistor pack and see if anything looks weird about it and do a multimeter check.

Today's lesson learned is: "Don't think that a part CAN'T be the problem just because it's new (or almost new)". Started troubleshooting my problem this morning by looking at the resistor pack (which checked out OK). I finally stumbled upon the idea that I should have tried FIRST. I hooked the blower motor to a jumper wire with DIRECT battery current, bypassing the entire ignition system and control circuits. The blower ran normally for about 5 minutes, then slowed, just like it's been doing. So, after a new blower motor installed (the old one was only seven months old), it looks like I'm good! Now to top off the freon level and actually get COLD air!

Glad you found it and got it fixed!

Don't catch frostbite.

joe_peters said:

The HVAC switch connectors like to melt. Pull it and take a look at the back side.

Good luck.

Click to expand...

So what is the fix for that? I pulled the dash apart to find the wiring completely melted at the back of the switch. Near as I can tell, I need to replace the wiring, relay and the switch. Does this sound about right? Is the dealership the only/best place to get these parts? Is the wiring difficult to trace?

Thanks,
Mike

http://www.jeepforum.com/forum/f11/...blown-melted-resistor-switch-wire-fix-580627/


I've not had the need to do it yet, but I'm on borrowed time in the '88-- it looks fairly straight forward once you dig into it.

Shorty said:

http://www.jeepforum.com/forum/f11/...blown-melted-resistor-switch-wire-fix-580627/


I've not had the need to do it yet, but I'm on borrowed time in the '88-- it looks fairly straight forward once you dig into it.

Click to expand...

Yep, same article I was going to refer to.