Blowers, resistors, wookies and Texas heat

First, I'm melting. Please help.

I've got a bad AC blower AND resistor. The blower started moaning a while back, but a few jiggles of the fan speed switch would usually fix it ...so i ignored it. Now, it's only working on high. I assume the evil (probably just off-balance or dirty) fan is the culprit for the dead resistor. The whole AC system has been due for a leak check and recharge since i bought the Jeep, but I'm only just now getting around to it. Before i go spending money i don't really have, I've got a question or two for you guys:

1. Is there a better than OEM replacement option for my '94? As in, can i possibly cram a blower and resistor from a 96+ into my dash without major modification?

2. Would this be a worthwhile upgrade?

3. Where can i find these parts for CHEAP? Local retail is about $60 for both parts. Are junkyard parts worth a shot? If so, any insight as to faults to watch out for?


That's all i've got at the moment. Any help would be greatly appreciated.
Thanks for looking.

Great forum by the way.

First, just replace the blower motor resistor pack. The default mode is "High" only when the pack is burnt out.

As for upgrades I don't know. The fan switch is also a known weak part.

Your blower motor is probably Ok.

It also sounds like your blower motor switch is on it's last legs. If you dig around, you can find where people have put relays in to take the current load away from the switch, which is a known weak spot. You say your blower motor is "moaning". This would also be a sign that it may be drawing excessive current. Normal procedure is to just replace the resistor and wait to see if it blows again. The resistor is a excellent junk yard part if you just take an ohmmeter to make sure that the thermal fuse isn't blown and the resistor doesn't look burnt. They don't wear out like mechanical parts. The motor is a different story, but you could hook one up to a battery and make sure it doesn't "moan".

Around 101* here officially today (just north of Houston) -- not a time to be messing about w/o AC in Texas. Probably hotter in DFW.

Your blower motor is likely the culprit and it is probably the bearings that are the problem. The motor does not have to make a lot of noise to draw excessive current and blow the thermal fuse in the resistor pack. The motor on my'93 had only the slightest squeak on occasion but after blowing a couple of thermal fuses I finally got the message. There are old threads detailing how some have drilled a hole in the face of the motor and oiled the bearing. I do not know what long term success they have had but you could always try it.

You can also save some bucks by replacing just the thermal fuse. These are available from Radio Shack for ~$2.00. Once you have the resistor pack out, replacing the fuse is simple provided you have a modicum of soldering ability. I've always soldered mine but you might get away with a careful crimp, particularly to determine that the problem is indeed the motor. Note the orientation of the old fuse before snipping it out. Also note that the fuse may not appear "blown" in the sense that it is "open", but it is bad if it shows any resistance over 0.0 ohms. I don't know what your soldering IQ is, but best to place some kind of heat sink on the fuse leads before applying heat.

You mention a motor for 96+? The same motor applies at least for '93 through '96. Not sure about newer models. AZ and O'Reilly locally have the same unit -- a Continental/VDO/Siemens PM272. O'Reilly is a bit cheaper (~$40.00?). When I did my '93 a couple years ago I also got the blower wheel for, I believe, $15. You probably won't need the wheel provided you can get the old one off without breaking it.

You may already know this, but you don't really get into the dash; the motor is not in the air stream and you replace the motor/wheel assembly from the engine side of the firewall. The job can vary from just a few minutes to a bit longer depending on what is in the way. On the '93 the only thing in the way (at least on mine) is the radiator overflow bottle which took a bit to get loose with some rusted screws. I think some model years have an AC component in the way.

The switch may be bad but I've never had a problem with one over 24 years of XJ ownership. Anecdotal as always. Jiggling the switch may have just altered the current to the blower motor enough to cause it to quiet for a period. At least you can hope this is the case!

As respects an upgrade, I don't know what all will fit, but I wouldn't even consider a new OEM unit -- Siemens/VDO are, as far as I know, still top quality components (if such a thing actually exists anymore).

Good luck. Get back if anything isn't clear.

Thanks for all the info. I think I might like this place...

I assumed the blower motor was on it's way out because of the moaning. I didn't realize that a bad resistor could be the cause the noise. I was thinking it was the other way around.

I'll give it a try with a bypass straight to the batt. Hopefully it's just be the resistor.

Would you guys happen to know what the resistance should be for these resistor packs? Or is that even a factor? From what you guys are saying, it sounds like the fuse should pop long before the coils give out.

@Pelican
-Do you have the specs or part # for that thermal fuse handy? My soldering abilities should be up to the task (insert caveat here).

Thanks again for the input, guys. I really appreciate it.

First let me say that a brief glance under the hood will confirm that you have to move the windshield washer fluid reservoir -- not the overflow bottle -- to get to the blower motor.

Second, the motor is usually the cause of the thermal fuse failure as you assumed. As the motor draws excessive current, it causes the resistor to overheat and the thermal fuse blows to protect the components from melting.

When you remove the resistor pack, you will see that there are three open wire wound resistors. If they are intact, e.g. not rusted through, they are probably okay. Use your meter to confirm continuity.

I happened to keep one empty package from Radio Shack: part no. 270-1320 for a 291.2* F (144*C) fuse. They come in various ratings and I got several different ones that were closest to the one in the resistor pack. An exact match is not that important.

They have a cabinet with a bunch of drawers, probably with one marked "Fuses", and look for a bin with Thermal fuses.

I wanted to add one thing. After replacing the thermal fuse the first time the fan worked properly on all speeds for a period of time, perhaps a week, before it blew again. This may or may not be typical but thought I would mention it.

I have no experience with junkyard parts such as the motor (no yards locally) but I assume you have little to lose by trying them. I don't know what the typical life of these motors might be, but the one in my '85 lasted for 23 years.

Let us know how it goes.

Insist on trying the motor at the JY wiring to a 12 V source. You should be able to tell if it works smoothly and quietly. Some motors last decades, while others go bad in months (even when new).

I sincerely appreciate all the info, fellas. I've been putting this off for so long now, mostly because I had the feeling it was going to be a never ending series of trips to Napa (and a few to AZ *cringe* for afterhours whatnots).

Once it drops out of the triple digits tonight, I'll go give this a look. I'm keeping my fingers crossed, hoping it's just the fuse. I'll still be a ways away from having AC, but at least one part of the system will be working. Once I get the leak(s) detected/fixed and recharge, I should be ok. ...of course, it'll probably be November by then, but ...yeah.

Oh and thanks again, Pelican. Hopefully, I'll be making a trip to the ol' radio shed later tonight. My XJ does seem to have that magic touch as far as consumable parts go. Her last brake pads on lasted 9 yrs! W@@t!

Thanks again, all. I'll keep y'all posted and I'll take some pics if i come across anything spooky.

Here's an update:

I've pulled the resistor and the thermal fuse is indeed bad. No continuity.

With this much oxidation, is it even worth trying to salvage the assembly, or should i go ahead and hit the junkyard? Is this the average condition of these things?

Good, bad, or just ugly?

Resistor pack is cheap at the dealer, and probably your main problem, they get wet, red hot, wet..... and rust away over the years. Fan switch in the dash could be bad too, they are frequent sources of fan speed failure. I would pull the resistor pack, 5 minute job, and inspect it first for burned out wire coil resistors, or thermal fuse. A non running, or slow running (bad bearing, or trash in the housing) blower could trip the thermal fuse!

Could be trash, leaves, in the blower housing.

So what about the wookies?

Probably typical. Doesn't look too bad to me. I would clean up the plug contacts a bit and check for continuity with the coil leads.

Playing with things electrical is a lifelong hobby for me and I tend to be very conservative when it comes wiring and components. In a case like this, though, pretty much the worst thing that could happen if one of the contacts does eventually corrode through is loss of a fan speed and a few minutes replacing the pack. Just my thought for what it's worth....

Of course if you are out at the JY looking for a motor and come by a good looking one you can always grab it.

Ecomike posted while I was composing.

Hey Mike, that's what he did -- you're looking at the result. The Chronicle keeps talking about us having a heat wave and drought like 1980. I don't remember the temperature so much but do remember the lakes drying up. In any event, I'm trying to save 13phix a trip to the yard since I've gotten old and don't really like to think about going out and rummaging through a bunch of old motor vehicles in this heat.

Pelican said:

Ecomike posted while I was composing.

Hey Mike, that's what he did -- you're looking at the result. The Chronicle keeps talking about us having a heat wave and drought like 1980. I don't remember the temperature so much but do remember the lakes drying up. In any event, I'm trying to save 13phix a trip to the yard since I've gotten old and don't really like to think about going out and rummaging through a bunch of old motor vehicles in this heat.

Click to expand...

I heard we have set something like 5 days of record temperatures here in Houston, going back to the oldest records in 1900. And yet many here still don't believe in global warming. But getting back on topic, I hear ya, I spent all day out in the sun on concrete last week helping a friend swap 4.0 engines. Nearly killed this old man.

I have never seen temps here over 100 in all my 54 years, and the ones I did see were in August, not JUNE!

I agree his resistor pack does not look bad. If it were me I would hot wire the blower for a test. Then pull the dash fan switch for inspection next.

I actually have my 85 Jeep blower hot wired to a 30 amp toggle switch under the hood. Been like that for 4 years now, never got around to fixing it right.

Pelican said:

Probably typical. Doesn't look too bad to me. ...

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Right on. I'll give it a once over with some deoxit and wire brush. Now i just gotta muster up the cojones to brave the trip to radio shack. Thermo on my front porch is reading 101.7 at the moment ...and that's in the shade. :wierd:

I keep hearing people comparing this heat to "that wave back in '80..." too. I wasn't born 'til '81 so i guess i should appreciate having missed that one. I can't even imagine what it must feel like down y'all's way. Last time i was in Houston i remember feeling like i needed a machete to cut through the humidity. I feel for you guys.

Ecomike said:

...
So what about the wookies?

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No sign of wookie activity yet. I ran the fan for a few minutes when i pulled the resistor pack and it seems to have taken care of it, though i could only test it on high and Chewy tends to make his appearance on low/med.

13Phix said:

Right on. I'll give it a once over with some deoxit and wire brush. Now i just gotta muster up the cojones to brave the trip to radio shack. Thermo on my front porch is reading 101.7 at the moment ...and that's in the shade. :wierd:

I keep hearing people comparing this heat to "that wave back in '80..." too. I wasn't born 'til '81 so i guess i should appreciate having missed that one. I can't even imagine what it must feel like down y'all's way. Last time i was in Houston i remember feeling like i needed a machete to cut through the humidity. I feel for you guys.

Click to expand...

I have been here since 55, I have never seen these temps before, and certainly not in June!