Help me with this blower problem

Ive been searching and searching but just want a few opinions before i start tearing into my dash and buying potentially needless parts.


'88 4.0 - Heres what happens...90% of the time my blower will not work at all. I can hear the climate control unit switching and stuff when i go from a/c to vent to heat to defrost, so it seems to be working. Occasionally I will start it up and the blower will work just fine, at all speeds. At first I though it might be a bad ground or a a few wires that have stripped themselves over the last 20 years touching each other. But it does not cut in or out wile driving like a loose wire would cause it to do. I'm thinking maybe the ignition switch is bad? But then again everything else works, all interior lights and radio work. Anyone had a similiar problem? What could cause it to work sporatically like this?


Help its starting to get cold and I need my defrost/heat


Thanks, Dan

the fan switch maybe?

id think a meter would narrow it down for ya if its calling for fan and ya got 12v at the motor and no fan ya need a mtr

kennzz05 said:

id think a meter would narrow it down for ya if its calling for fan and ya got 12v at the motor and no fan ya need a mtr

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same method can be used to check the switch and all other parts. If theres power goin in and none comin out (of the switch) you've found your problem. I have run into this before and it was the fan switch sticking. Not sayin thats definitely it but its definitely worth checking.

Sounds like the blower motor resistor is going bad.
A quick search listed all these threads. Replace the resistor, it's fairly quick and easy.

MT Mike said:

Sounds like the blower motor resistor is going bad.
A quick search listed all these threads. Replace the resistor, it's fairly quick and easy.

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Usually when the resistor goes, you lose some, not all, of the speeds. And if it does fail once, its burned out and won't start working again on all speeds just to quit again completely like the op said. I'd be looking for a loose wire/short or a bad connection somewhere else. Could be the motor too though. Just use a meter or even a test light to check all of the components

BudgetXJ said:

Usually when the resistor goes, you lose some, not all, of the speeds. And if it does fail once, its burned out and won't start working again on all speeds just to quit again completely like the op said. I'd be looking for a loose wire/short or a bad connection somewhere else. Could be the motor too though. Just use a meter or even a test light to check all of the components

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Not true. Key word is usually. I've seen a few Dodges that the fan would intermittantly work on, a new resistor solved the problem.

I'm not telling him not to bother checking power in and out of the switch, just suggesting that if he finds that he has both of those to try the replacing the resistor. It is a fairly inexpensive and easy part to replace.

fair enough. I would recommend checking for power in and out of the resistor before simply replacing it though. Not that I think you wouldn't. I'm just saying always take the time to check something for faultyness before assuming its at fault. Even if its the last part of the system. I've been bit by throwing parts at a vehicle in the past and therefore wouldn't recommend it.

A quick check to see if it may be a 'dead spot' in the fan motor---
turn the fan on, roll up the windows and slam the back hatch...hard...

the resulting pressurizing of the cabin area can move the fan motor off of the dead spot (this dead spot is usually caused be one coil going bad)

Well thanks everyone so far....guess i'll bust out the multi-meter tomorrow and check for power going into/out of the blower switch, as well as the blower resistor. Still baffling as to why the whole thing works fine sometimes and not at all other times, seems like a little troll lives in my dash and every time I start the XJ up he decides if I have a blower or not:dunno:

My Dodge Ram had a similar issue. The fan would not work on high most of the time. It turned out that the switch setting for high had become very corroded. the increased resistance caused the switch to get hot and distort. the stealership quoted me an unGodly price for the new switch assy. I was able to clean the switch and make it serviceable again.

check for power before and after the switch, resistor, and motor. make sure the connections are clean. if not, clean them.

hth
stewie

The blower resistor is used for all speeds EXCEPT high.... if you have no blower operation at all, it is probably not the resistor.... Blowers carry high current and it is not uncommon for them to melt a connector.... I would check for power and ground at the blower motor first and inspect the connector for corrosion, correct terminal tension and melting..... wiggling the connector with the blower turned on might show a connection problem.....