[Nof-z]

Hello all! I have had a problem with my heater blower motor that's a little odd... so the blower only works every once in a while, and continues to work until I forget to turn it off before I turn the jeep off, otherwise it does't work for a week or so, the decides to turn on. all of the other dials still work (temperature and blower speed) and let air into the vehicle when they are on, regardless of if the blower direction knob is working or not. Any ideas? Its already winter here in montana and I kind of need my defogger. Thanks!

Basic jeep info:
2002 tj, 4.0, no A/C, all fuses good, haven't checked relays, temp knob works, wind speed knob works (in that it at least lets air in when I turn it,) on/off/direction knob works intermittently.

 

[BM3]

Might need to check the connections behind the HVAC control box. I know some have had problems with melted/damaged connector. This link might have some good info in it for you
https://www.jeepforum.com/forum/f9/tj-hvac-melting-solved-2970721/

 

[jtec]

agree the wiring overheats at rear of HVAC module.

link should help you remove - to check electrical.. We could get a diagram and check wiring if you are comfortable with diagram and a test light.

 

[jtec]

attachment

 

[Nof-z]

excellent, thank you! I will check that and see if that's it!

 

[Nof-z]

alright, I pulled it apart and there is no sign of melting or burning. Is there any other things inside of the unit that would make this happen?

 

[mukluk]

If you're having problems with the mode selector not making the air come out of the appropriate vents, then you aren't having a blower motor problem, you have a vacuum switch problem. All the mode doors are controlled via vacuum, not electrically. The default position with absolutely no vacuum applied is to have air coming out of the defrost vent and nowhere else -- if this isn't your case, you are getting vacuum to the mode switch and to the door actuators, but it's going to the wrong place.

 

[Nof-z]

the problem isn't that where the air come out (that works fine, I can tell through forced induction) the problem is that the blower motor only works intermittently

 

[Stumptown]

So you have an intermittently working blower motor? Can you thump the motor with something to see if that gets it to work?

When it isn't working, do you have power at the speed switch? This will tell us if the issue is upstream of the switch or downstream.

Anything else not working or working poorly? This would tell us if there is an issue upstream like an ignition switch, or possible issues in the PDM.

 

[Nof-z]

no, nothing else is working poorly, at least as far as I can tell... My multi-meter chose today to die, so I have to buy a new one. I'll let you all know what happens with it tomorrow, when I can drive to the city to get one.

 

[Nof-z]

Alright, I got a multimeter onto it all, and the mode selector and heat stitch gets power, but the air speed knob isn't getting power. Any ideas?

 

[Rubi4MyMrs]

I'm not sure how you are testing the circuit with your meter. If you are using a voltage scale you will likely get false & confusing results. This circuit controls the fan on-off & speed functions through the ground side of the overall circuit with 12v power only going to the blower motor.

If you test the ground side with a volt meter you can get "false" 12v reading if the actual ground is bad. That is because the meter's circuitry becomes the grounding path & the meter (falsely) reads voltage. What you really need at the speed & mode switches is continuity to ground, not voltage.


Use the circuit diagram posted above. The A wire on the blower motor needs 12v, the B wire needs ground which must pass through the speed (5-8) & mode (1-4) switches to get to the ground point at G-202.


The first thing to test when the failure is intermittent is to wiggle the connector to the motor (when it is not working) to be sure you do not have a loose connection there. If you have 12v at that connector & a good connection when plugged in you then need to check the ground wire there using the ohm scale on your meter & check for continuity to ground. If you have a good ground reading but the motor does not run, the motor is bad. If you do not have a good ground (no continuity) here is a link with a troubleshooting procedure for the grounding circuit. After following it you may want to read through the rest of the thread for more info if needed.


http://www.wranglerforum.com/f210/t...arding-the-blower-fan-28486.html#post15939209

 

[jtec]

jeep blowers work a little different, the blower motor is HOT in run,
And is looking for a ground - either Hi speed which is blower direct to ground OR blower thru the resistors to ground.


this diagram is circuit BEFORE the above attachment for blower resistors.

 

[Nof-z]

okay cool, I will check those out. I did replace the blower motor, though for other reasons, as it go flooded when I got stuck in some deep mud... bad ground does sound like something that would make sense. would this be caused by a bad resistor?

 

[Nof-z]

update time! I went through all the wiring and nothing was clearly burned or dislocated, so I turned the jeep on and fiddled with all the wiring to see if there was a short. about ten seconds after start up, right as i touched the blower motor connector, the thing started up! so I wiggled that wire a fair bit to see if it turned off, and it stayed on. thinking I was an idiot who just had a bad plug connection for the past two months on both the old and new blower, tried all the control knobs. they all worked except the fan speed controller. as soon as I messed with that the whole hvac system stopped blowing. now I am more concerned than ever...

 

[cvariaex2]

Blower Motor Resistor helped me. Dorman 973-025 Blower Motor Resistor for Jeep Liberty/Wrangler https://www.amazon.com/dp/B003YLMPPA/ref=cm_sw_r_cp_apa_i_R7rRDbK2HX0RH

 

[Nof-z]

cool, I'll try that. I can't exactly afford to take this into someone, so is there a way if it doesn't work that I can just temporarily hard wire the blower on, maybe through a separate switch so I can at least have my defroster? Also, What does the resistor actually do? I'm terrible with the electronic side of cars...

 

[Rubi4MyMrs]

The resistor controls the blower speed but is bypassed for high speed so if the blower is not working on high, the problem in not the resistor.

Did you run the procedure in the link I posted? Your description now sounds like the problem might be at the speed switch, the connector may be bad (loose or overheated) or the switch may be bad. That is covered in the link.

Part of the procedure linked involves grounding various wires at the speed switch for testing. If nothing else, if grounding the high speed (or any speed) wire there gets it going you can leave it grounded (or add a switch) to have it working that way until you get it figured out.

 

[Nof-z]

yes I did, the motor gets power, however I cant find a good place to use as a ground to test the fan speed wires... either that or they are all bad

 

[Rubi4MyMrs]

OK, got it.Try this...


Once you have the panel out you can unplug the wire connector at the mode selector & find the black wire in that connector. That should be grounded so see if you have continuity between that wire & the grounding bolt behind & maybe slightly below the dash speaker, I think there is one on each side, for sure on the driver's side. If that is good use that black wire for your ground. Be sure the key is on & this is when the blower is not otherwise working (since it can be intermittent & you need to test when not working). Then unplug the speed switch connector & with a jumper wire jump from that black wire to each of the 4 wires, not including the dark green one, one at a time to see if you get each of the 4 speeds.

If good there, then remove the jumper wire from the black wire & connect it to the dark green wire in the speed switch connector, make sure the mode switch is now plugged into its connector & is in any position except off. Now jumping to each of the other 4 wires of the speed switch connector should also get each of the 4 fans speeds. If not, the mode selector switch is bad or you have a bad connection (loose or overheated) at the mode switch connector.

If you still have trouble getting a good ground you can run a long wire directly to the battery negative (-) post to get the best possibly ground point.

If none of this grounding works I would say you have a bad ground at the blower motor connection even though it seemed to be affected by turning the speed switch. Ultimately you need a good ground (and 12v power) to the motor for it to run. And that ground path runs through the speed & mode switches (as well as the resistor for speeds 1-3).



And with that, of course, you need a good motor.