ljamison2000

Hello! I recently purchased my 1999 XJ and fell in love. All was good until the cold Minnesota winter started. At first, the heater/blower would only work on a start where the car was completely cold. Now, it won't turn on at all, but when on high will push a little heat out (but with no fan or force). Someone help as it's sub-zero here and I cant see a thing out the windshield driving!! I understand it could be a fuse, the switch, or the relay: but I'm just not sure which. Since I know the fan works I have somewhat eliminated it as a problem. ANY help is appreciated.

PatHenry

A fuse should be very easy to check - if you don't have a reference for the fuse block near the fuses just Google it and go through each fuse.

The other thing you should always do is clean and tighten all your grounds just to eliminate it as a cause.

How do you know the fan works? "Somewhat eliminated"... either the fan spins strong and balanced when it gets power or it doesn't..

PatHenry

Another thing to check is the wiring around the blower motor resistor.
If they used the same components in the XJ as they did in the TJ (which hopefully they didn't) then there is a common problem with the wires/connector melting.

I was sorely disappointed with the heat/ac components in my old TJ.. the controls were poor quality, the resistor constantly failed.. etc etc.

​​​​​​​I remember coming out of hockey on a cold New England winter night and turning the dial and having it practically fall off in my hand.

ljamison2000

PatHenry,

fan works when the car is cold, but now it won't work at all. I have taken it out before to work on my engine and saw nothing wrong with it.

PatHenry

I'd check the fuses, though obviously a bad fuse will result in zero operation, so that's unlikely.
The relay is easy enough to test as well using a multi-meter or you can just replace it since it's cheap.

Clearly if the fan works when it's cold and not when you're at normal operating temp, something is getting hot and malfunctioning, so I'd go for a drive then immediately test the relay.

It's weird that temperature is an issue..

ljamison2000

Update:

PatHenry

If you haven't done so already, make sure all the grounds are clean and tight.

The next thing I would do is check that the fan is working strong and balanced when direct power is applied. I know you've said it's good - I'm just saying what I would do in your situation. I'd leave the fan installed and just pull the plug and run wires straight off the battery. It should kick on with force (since it's getting un-resisted current). I wouldn't run it for any amount of time, just verify it kicks on.

If the fan runs, I'd break out the electrical test tools and while I've got the plug out of the fan, check that the connector is not putting out power when the key is on and the fan controls are on high... obviously it SHOULD have power once your problem is resolved, but I like sanity checks.

KenR

LJamison,
If the blower motor spins even a little bit when cold, that is a clue. My Dodge did this. In my case, the blower motor was toast. This is how I tested it.
First, disconnect the blower motor pigtail from the connector.

Second, connect your multi-meter or test light to the harness side of the connector, key on-engine not running, blower on HIGH. Do not touch the two leads to each other. If the test light is really bright/multi-meter reads about 12.5 volts, you have good power to the fan motor. Dim light/low voltage, you most likely need the resistor. More on that later.

Third, With jumper wires, add power and ground from the battery to the fan side of that connector. Do not touch the two wires together. Did the fan spin like crazy? Yes? Fan is good. No? fan is toast or your wires became disconnected and need to be reconnected. Test again.

Fourth, If the resistor is the issue, replace it AND the fan motor at the same time. Fans are cheap and DO go bad, even if they spin fairly fast. My Dodge did this exact thing, and I had to do double the work, as I replaced the pieces at two different times only 2 weeks apart.

My two cents.

KenR

PatHenry

Ken's advice is sound - do the testing as he described.

If the XJ resistor was the same part/design as the TJ of the same year, the blower motor resistor is a piece of junk. They constantly fail (the classic symptom of this is that the fan only runs on high) and just plain suck.
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caged

if it's the same as my 99 xj, i had to keep tugging and moving the wire harness under the hood at the blower motor in the firewall. move it a little and it gets connection. i know i should have just went ahead and fixed my problem, but this at least got it working.

and i agree on the 99 TJ wiring. i had that happen with mine a few times, burned up a few control heads and wiring harnesses. i learned to grab any that was being parted out to keep on my shelf as i know one day i will have to change it again. the first one, i bought brand new from the dealer. don't want to have to do that again.

but i don't think the xj and tj shares the same problem.

Waynerd

The reason the resistor would keep failing is because the fan motor is worn and requiring more current to operate. There's a very high probability that if the resistor fails then the blower is wearing down. It's always a good idea to replace the blower also.

Sometimes it could also be the back of the control **** where the connector plugs in that's been melted from the extra current draw. That could also cause only high to work or to not work at all. I would check both connectors first. The one at the resistor and at the control.