my heater fan comes off and on intermittently.it will do it when hitting bumps or slamming car door and just at idle.i replaced the switch some time back becaused it fried.so i tore into the dash and wiggled all the wires all the way down to the resisitor and nothing made it go off. could the actual heater control box be bad?
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intermittent heater fan?
- Thread starter mudrat
- Start date
JWheeler
NAXJA Forum User
- Location
- Washington
Why wiring and controls? Have you replaced the blower motor?
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
I would put my money on an intermittent open circuit--might even be internal to the motor.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
An open circuity could happen anywhere--a loose connection, busted soldered joint, etc.
This is one of things that is hard to locate until it stops working completely.
Davinator61
NAXJA Forum User
- Location
- Kent, Washington
Sorry about giving this thread a Necro-Rez, but I've been having the dreaded "Intermittent Heater-Blower-Fan Syndrome" for about a year, on my 1991 XJ Laredo(4.0L, AW4 auto-trans, NP242 xfer-case, D30-front, D35-rear, etc., etc., etc.), and found, in my case, it was just the connectors to the blower fan motor & resistor pack that were either dirty, mildly corroded, or 6-of-1, 1/2-dozen of the other. A few shots of Amsoil MP, from a can I've had sitting around a few years, and unplugging, and replugging in, each connector a few times, seemed to do the trick of both cleaning off the dirt and/or corrosion from the contacts, 'cause now the fan comes right on when I set the Function Selector to Heater, Vent, or Defrost(no A/C though, as the A/C system's components have been completely removed from my "HEEP"), as it used to take a few seconds for it to come on before, whenever it chose to work. If the problem comes back, I'll likely re-check those connectors, as well as the multi-function switch & the blower fan speed control rocker switch connectors as well. If I've gotta replace anything, I'll start with the resistor pack, as they do get really nasty after a few years of doing their job. After that, time, and further testing, will tell. Hope this helps, maybe...
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Necro-Resurrection Pt.2 :
( '94 XJ ) Heater Fan doesn't turn on at all (any speed), then suddenly starts one day - ALL speeds.
Now, back to no start.
So before ordering the cheap Amazon motor, tried banging it & slamming doors, etc, but won't start. ( Vacuum continues to be fine, since it still makes that "exhale" sound, when sliding setting to Heat ).
1 very old post suggested maybe it's the Switch ? Anyone determined what the fix actually is ?
( '94 XJ ) Heater Fan doesn't turn on at all (any speed), then suddenly starts one day - ALL speeds.
Now, back to no start.
So before ordering the cheap Amazon motor, tried banging it & slamming doors, etc, but won't start. ( Vacuum continues to be fine, since it still makes that "exhale" sound, when sliding setting to Heat ).
1 very old post suggested maybe it's the Switch ? Anyone determined what the fix actually is ?
- Location
- In a strange land
Have you pulled the dash bezel and the heater control to take a look at the connector on the back side of the fan speed switch?
Have you taken out the resistor and inspected it?
If you have not yet done either of those things then that is where I would start.
If both of those are good I would then check grounds.
My next suspect after those three would be the fan motor itself, but I think that is an unlikely culprit. The previous items are more likely to be the problem.
Have you taken out the resistor and inspected it?
If you have not yet done either of those things then that is where I would start.
If both of those are good I would then check grounds.
My next suspect after those three would be the fan motor itself, but I think that is an unlikely culprit. The previous items are more likely to be the problem.
NOTNSUV
You Guys ROCK!
- Location
- Spring Creek, NV
Nope
Nope
Resurection. Just experienced complete failure (even on High) of fan after years of intermittent. YouTube search led me to the relay behind the glovebox (99) which I replaced to no avail. I'll run down the list above. I've checked the 15a fuse under the dash and the 40a under the hood, both are good. My understanding is the fan should operate on High if the resistor is the culprit.. makes perfect sense.
I have zero from the heat/ac. No compressor powered, no fan at any setting, zip/nada. I'm leaning toward the control panel so will dig into that.
Long time since I've posted here; I've been off in TJUR land and the XJ just keeps plugging along as my winter DD and the rig I hammer.
Unclewolverine
NAXJA Forum User
- Location
- Kansas
I mean, it's a really simple system. Just follow the 12v path. Pull the controls, test for 12v at the switch. If it's not there then your problem is at the fuse box. Follow the flow of power from there, my guess is either your switch or the switch plug is bad. I've seen it before on mopars. But xjs are getting to the age where we are getting wire failures from cracks, fatigue, and rub through.
