The infamous Blower motor/Switch/Resistor problem... should be quick - JeepForum.com
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post #1 of 43 Old 03-03-2009, 07:58 PM Thread Starter
EEKizzle
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The infamous Blower motor/Switch/Resistor problem... should be quick

I'm brand new to the forums here, have an '01 Sahara and I've been searching frivolously but I couldn't find what I was looking for.

Unlike most, my 1st and 2nd speeds work fine but my 3rd and 4th speeds have failed. Upon removing the the whole AC/Heat control unit 2 of my spade connectors (this is not the first time its failed) are melted.

I'm an electrical engineering student so I'm assuming since the speeds 3 and 4 have less resistance and therefore more current (and also faster fan speed) that indicates that the blower motor is drawing more power which has made the current high enough to melt the wires.

I've read that that happens with age/dirt/wear, but I can't find more than a sentence on it.

So really I am looking for some confirmation, is it the blower motor or could it be something with the relay that I don't know about? Even if the switch has failed its definitely not the root cause and I'm fairly confident its not the resistor since lack of resistance seems to be the problem. Thanks for the help, I appreciate it!

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post #2 of 43 Old 03-03-2009, 08:06 PM
Cchandler
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My third and 4th speeds didn't work and it was just the switch. 20 bucks new at the stealership. If you take the control panel out of your center console on your dash and look at your fan speed switch most likely it will be brown on one of your contacts from where too much current was drawn through it and it will smell like it was burning. I know that's what mine looked like. You might try to tap on the switch to see if it comes on. If it does like mine, it's definitely the switch which is cheaper than the enitre new blower motor resistor. Good luck!
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post #3 of 43 Old 03-03-2009, 08:08 PM
Cchandler
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Because your high speed setting, the 4th speed doesn't use your blower motor resistor at all. So that should tell you right there it's just the switch or the wiring.
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post #4 of 43 Old 01-09-2010, 07:43 PM
lam4eks
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Hi,
I had only 3 and 4 working for the past two years. then last week only 4 worked so after much research and searching on here I found this. I got mine at NAPA auto parts for $20.00. The only thing different was i unscrewed teh little light on the bottom which made it easier to take the resistor out still connected to the wiring. Seeing the connector made it a whole lt easier to disconnect.
Thanks,
Larry
BTW this was on a 2005 Unlimited with a 6spd
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post #5 of 43 Old 01-09-2010, 08:01 PM
garbon2535
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To test the blower motor switch 1st remove the heater-A/C control unit (which you have already done). Next turn the ignition switch to the "on" position and check for battery voltage at the fused ignition switch output circuit cavity of the heater-A/C mode control switch wire harness connector. If not OK then you will need to repair the open circuit to the fuseblock module. If OK then goto the next step.

Next step is to select any of the heater-A/C mode control positions except "off" to turn the system on. Check for battery voltage at the low blower motor driver circuit cavity of the heater-A/C mode control switch wire harness connector. If not OK then replace the switch. If OK then goto the next step.

Next step is to check for battery voltage at the low blower motor driver circuit cavity of the blower motor switch wire harness connector. If not OK then repair the open circuit to the heater-A/C mode control switch wire harnes connector. If OK then goto the next step.

Next step is to check for battery voltage at each of the remaining blower motor switch wire harness connector cavities as you move the switch to each blower motor speed position. Voltage should be present in each cavity at only one switch position. If not OK then replace the switch. If OK then move on to testing your blower motor resistor and/or relay.
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post #6 of 43 Old 01-09-2010, 08:34 PM
Djay101
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my 1998 jeep tj heater just has the 4th working on it. is it the resistor?
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post #7 of 43 Old 01-10-2010, 09:57 AM
JBTJ
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There are a couple of factors that lead up to the failure of the melting fan switch. First is the design of the circuits involved. Second would be the blower motor. After some time the motor starts to pull more current due to wear. Third would be the undersized wire used in these circuits. As this additional current flows through these items, that weren’t designed to handle the excess current, they begin to overheat at the contact points and we have switches and resistor packs failing.

A fix to this problem which also has some options, depending on how far you want to go. The circuits design has the switch controlling the blower motor speeds, which is a bad idea. Adding a relay in the circuit will allow the relay to control the blower motor and the switch simply controls the relay. So therefore the switch will no longer see the excess current, only the relay will.

The blower motor is rated at 30 amps so you would want to use a 40 amp relay. You will also need to add this relay for each fan speed. You could also upgrade the wire size in these circuits to something like 14ga.

I have done this mod on my JEEP as several others with great success. I have not replaced my blower motor yet, but others that did this mod have. I guess it would depend on how badly worn the motor is. But, you may just want to go ahead and replace the motor, switch, resistor pack and maybe the mode switch as well as I have done. If you do a search around here I posted a write up that should help you fix this problem once and for all.
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post #8 of 43 Old 01-10-2010, 10:00 AM
billymac4511
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Quote:
Originally Posted by Djay101 View Post
my 1998 jeep tj heater just has the 4th working on it. is it the resistor?
Almost definitely yes.

That's the common 'blower motor resistor' issue. Replace the resistor and things should be just fine.

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post #9 of 43 Old 01-10-2010, 11:29 AM
WILLY348
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Replace the resistor and call it a day tbh

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post #10 of 43 Old 01-23-2010, 05:28 PM
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any photos showing where it is?
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post #11 of 43 Old 02-15-2010, 07:11 PM
epeck87
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Quote:
Originally Posted by JBTJ View Post
There are a couple of factors that lead up to the failure of the melting fan switch. First is the design of the circuits involved. Second would be the blower motor. After some time the motor starts to pull more current due to wear. Third would be the undersized wire used in these circuits. As this additional current flows through these items, that weren’t designed to handle the excess current, they begin to overheat at the contact points and we have switches and resistor packs failing.

A fix to this problem which also has some options, depending on how far you want to go. The circuits design has the switch controlling the blower motor speeds, which is a bad idea. Adding a relay in the circuit will allow the relay to control the blower motor and the switch simply controls the relay. So therefore the switch will no longer see the excess current, only the relay will.

The blower motor is rated at 30 amps so you would want to use a 40 amp relay. You will also need to add this relay for each fan speed. You could also upgrade the wire size in these circuits to something like 14ga.

I have done this mod on my JEEP as several others with great success. I have not replaced my blower motor yet, but others that did this mod have. I guess it would depend on how badly worn the motor is. But, you may just want to go ahead and replace the motor, switch, resistor pack and maybe the mode switch as well as I have done. If you do a search around here I posted a write up that should help you fix this problem once and for all.
i lost all fan speeds one at a time over about a week so i bought a new resistor ($40) for mine and that didnt fix anything then i discovered my switch was melted so i ordered a new switch at the dealer today for $20 but i really dont feel like wiring up relays if i dont have to... im just lazy lol. i read in another thread on the forum that what happens is the brushes in the motor wear out and draw more current as they wear so if i just throw in a new switch is it gonna burn up immediately or can i expect to get a couple years out of it before it goes up again? if it is true that the old motor is whats causing the meltdown i might replace the motor which i hear is over $100 but if i can get another 10 years out of it it might be worth it to throw a new motor and switch at it if the worn brush theory is in fact correct. the jeep is a 2000 with just over 100,000miles.

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Last edited by epeck87; 02-15-2010 at 08:00 PM.
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post #12 of 43 Old 02-26-2010, 08:45 PM
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post #13 of 43 Old 02-27-2010, 04:34 AM
bdevr
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Quote:
Originally Posted by Djay101 View Post
any photos showing where it is?
Check this out

Jeep Articles / Technical and Installation (Blower Motor Resistor Fix) - MoabJeeper Magazine
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post #14 of 43 Old 02-27-2010, 08:43 AM
Border Dave
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And here's a link showing how to protect the switch with relays. It's been working well for me for about two years: Fried blower switch fix - JeepsUnlimited.com Forums
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post #15 of 43 Old 02-27-2010, 09:35 PM
99XombieTJ
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I have the 4, 40 amp relays, a brand new switch, a brand new blower motor-switch wiring harness, a new blower motor and a new resistor. I need a wiring diagram or photos detailed enough that an electrical idiot like me can follow. There are tons of great diagrams but I dont know how to read those darn things.
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