Small electrical problem

1990 ,4.0 , no AC

The interior fan won't work, as in it's dead quiet when i turn the vent or
anything else for that matter (heat, defrost, etc.) on. it's not the actual selection on where the air will go thats the problem but rather the fan blowing the air, so i suspect a electrical issue.I have checked the fuse
( i think its the "blower" one) and its good....... what's my next step????

Also i saw a nifty diagram of the fuse box for the pre '97 XJ's does anyone know a link to that?

First check to make sure the blower does not work at any speeds. If it turns out to work at high speed only, the problem is in the resistor pack, which is found in the heater box, down near the passenger's feet. You'll see a little plastic cover, with wires disappearing into it. There's a diode in the resistor pack that sometimes blows, and I think if you search you might find someone's post on fixing that with a Radio Shack part. Otherwise of course you can also simply replace the component.

If it does not work at any speed, you can test the blower itself and the wiring to it if you have a test light or meter. First unplug the blower motor in the engine compartment, probe the connector from the vehicle with a test light and see if you get a light. If you do, then you know the motor is getting power. If you don't, you'll need to trace the problem back. The switch can sometimes melt, so that's a good thing to check first. The motor is easy to get out. I think on a pre-91 you'll have to move the coolant tank. The blower attaches with 3 screws and pulls right off.

Unfortunately, the motor is held together not by bolts but rivets, and this means that it is not designed to be serviced. I have had some success in getting one apart to lube the bearings, but it's very easy to break the hub of the plastic fan trying to get it off the rusty shaft, and the bearing fix only lasted a couple of years.

Matthew Currie said:

First check to make sure the blower does not work at any speeds. If it turns out to work at high speed only, the problem is in the resistor pack, which is found in the heater box, down near the passenger's feet.

Click to expand...

http://www.geocities.com/chmwatson/FAQs/Jeep/HVAC-fuselink_fix.html

Check to see if the blower motor itself works. Use a volt meter or test light to probe for 12v at the connector to the motor, or just run a good 12v source to the motor itself directly and see if the motor runs.

If the motor is bad, you want to make sure it didn't go bad because of water inside the heater box. Make sure it's dry and there's no rust on the motor when you remove it.

If you find that the blower does work, check the vacuum lines. I found 2 broken lines. They were behind the passenger side taillight in the engine compartment, below the battery. The vacuum lines run from the bottle located behind the bumper.

Before, when I turned my A/C on, it did absolutely nothing. A quick trace of the vacuum lines(had to remove the battery from the vehicle to get to the cracked hoses i found) turned up my problem, I cut the plastic vac line in half and slipped some rubber tubing over it, recharged the compressor(it all leaked out =[) and turned it on...problem solved.

UPDATE


thank you all for your useful info the motor problem has been solved but a new problem has occurred ......it is vacuum ,it only blows in defrost

so i have to find a break in the vacuum line what is the best was of doing this?? and how do i "recharge the compressor"?

Samman said:

UPDATE


thank you all for your useful info the motor problem has been solved but a new problem has occurred ......it is vacuum ,it only blows in defrost

so i have to find a break in the vacuum line what is the best was of doing this?? and how do i "recharge the compressor"?

Click to expand...

According to your first post, you don't have A/C, so recharging the system means nothing to you. You don't have a compressor.

There's a thin black vacuum line on the passenger side of the engine compartment, runs from the firewall down past the ignition module area and into the vacuum canister in the bumper. You've gotta find that line and make sure it's intact, chances are it's broken. If it is intact, keep following vacuum lines to and from the canister, if everything is OK, the problem is inside and you're gonna have to take the dash apart to fix it.

First, I followed my vacuum lines listening for a whooshing of air, that's how I found the first one...then I ran my hand down the lines and I felt the air on the second one, that's probly the easiest way of finding your leak(assuming you have one)...

as far as the fact that it only blows in defrost, it is MOST LIKELY a vacuum problem. I had the exact same problem, defrost only. that's what led me to tracing the lines.

The first place you need to check is the vacuum bottle, make sure that there are no hoses that are not attached here. 2nd, check the line(s) below the coolant bottle, I've seen several cases of breaks here. 3rd, and the biggest PIA in my opinion, is deep in the front passenger corner of the engine compartment. I had to remove my battery to get down to the lines. If you find no leaks there, go ahead and just run your hand down the lines and see if you turn up anything. if you find nothing, grab some tools and head for the dash =(

since you don't have A/C don't worry bout the compressor thing, I apparently didn't read your first post thoroughly

Thank you all again for your knowlage, followed the advice for checking lines and there was a small leak near the collant bottle .....good to wheel again !!!!

Congratulations! Ain't it sweet not havin to tear the dash apart? lol