1. #1
    Jeeper99's Avatar
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    Iffy Blower Switch.

    I had a new issue occur with my fan control switch today. Several months back, the 3rd (or medium High) setting on my blower switch quit working. Low, Medium and High worked fine. Now today, The blower was working fine and just quit. None of the settings are working, which leaves me with no heat!

    I've read about some of the blower motor resistors and all that, but not sure what to do.

    Thanks for any help guys!!
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    Re: Iffy Blower Switch.

    no idea on what to check on those new jeeps but there has to be a resistor somewhere in it
    I love my old jeep.

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    Re: Iffy Blower Switch.

    There are a few things to check besides the resistor. Like the fuse, relay, speed select switch and wiring and lastly the motor itself. The high setting does not usually fail as it is a short with no resistance between pins.

    Pull the resistor and measure the resistance between posts. There should be some continuity. If they are blown it will show and infinite resistance. The high setting should be really low resistance.

    Failing resistors can be a sign of a dirty or failing motor should your resistor go again, I'd look closely at the motor.

    Here is a you tube video.
    http://http://www.youtube.com/watch?v=kikg3uoeNLc
    Last edited by JPNinPA; 12-18-2011 at 10:07 AM.
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    Re: Iffy Blower Switch.

    Thanks for the advice! If the resistor is bad, would it fail to work on all 4 settings, then the next day, be working again? For some reason, that' what happened. THe next several days after my initial post, all but the third setting was working again.

    But today, none are working.... For what it's worth, the temps have dropped into the low 20's here as of the past couple of days. Don't know it that would affect anything or not.

    Thanks again for the help!

    Jon
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    Re: Iffy Blower Switch.

    No the resistor is unlikely to heal itself. These are metal resistors that burn open when they fail. The highest setting is a dead short and should work given there isn't worse things going on.

    I'd look at the wiring and connectors from the switch to resistor and motor. This is another common failure.
    Last edited by JPNinPA; 12-30-2011 at 07:08 AM.
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    Usually a resistor when failed leaves you with high speed as its a direct 12 v there's no "resistor in the circuit for high speed. I would lean more towards a motor or switch.

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    Re: Iffy Blower Switch.

    Previous Poster is correct. If the Resistor were Bad. --- ONLY the High speed position on the Switch would work. (12V is applied directly to Fan Motor). Most likely it is the Fan Motor Itself or the Switch. Easiest way to narrow it down : Pull Electrical Connector from the Fan Motor --- Useing a Couple of Jumper Wires--- Wire the 12Volts directly from the Battery to the Fan. (Observe Polarity) When you hook-it-up: Does the FAN COME ON? If it does come on --- THEN it is the Switch OR a wiring Issue -- IF it does. NOT come on (direct 12V)-- THEN IT is the Fan MOTOR. (Bad motor). Also, this Jeep is a 1999 TJ --- Correct? Strictly a Manual Temp. Control System??? Good Luck! JB

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    Re: Iffy Blower Switch.

    Thanks guys, I'm going to see if I can pinpoint the issue and I'll let you know what I find! Thanks alot for all the info! It's greatly appreciated!

    Jon
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    Re: Iffy Blower Switch.

    Quote Originally Posted by jimbob2001 View Post
    Previous Poster is correct. If the Resistor were Bad. --- ONLY the High speed position on the Switch would work. (12V is applied directly to Fan Motor). Most likely it is the Fan Motor Itself or the Switch. Easiest way to narrow it down : Pull Electrical Connector from the Fan Motor --- Useing a Couple of Jumper Wires--- Wire the 12Volts directly from the Battery to the Fan. (Observe Polarity) When you hook-it-up: Does the FAN COME ON? If it does come on --- THEN it is the Switch OR a wiring Issue -- IF it does. NOT come on (direct 12V)-- THEN IT is the Fan MOTOR. (Bad motor). Also, this Jeep is a 1999 TJ --- Correct? Strictly a Manual Temp. Control System??? Good Luck! JB
    I have the basic understanding of a resistor and the colorcodes on them ,and about electricity. but I have a question on what would make the resistor go bad,isn't it made up of carbon? Does age effect it?

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    Quote Originally Posted by gennybro
    I have the basic understanding of a resistor and the colorcodes on them ,and about electricity. but I have a question on what would make the resistor go bad,isn't it made up of carbon? Does age effect it?
    A motor going out causing excess draw will burn them up. Age. Heat. Vibration. If the motor has a tough spot or was froze at one time they will pull more current and create alot of heat. I've seen some that melted the connector to the resistor.

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    Re: Iffy Blower Switch.

    op, you said the temp dropped and it quit again? does it only give you trouble when its cold? maybe the motor is somehow freezing up?
    I love my old jeep.

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    Re: Iffy Blower Switch.

    Yes --- A Motor going OUT would DRAW excessive Current---Causing the Resistor to: Burn out. Resistors (an electronic component) are RATED by the Manufacturr in: 1. OHMS And 2. POWER Example: A Resistors Specs would be: 330 Ohms and 1 Watt. IF you EXCEED the Power Rating FOR any Length of Time--- The Resistor will OPEN. (Burn out). Resistors CAN be made of: Carbon, Wirewound, and Metal Film. (To name a few). A previous Poster raised this Issue-----Back to the - " IFFY Blower Switch". Possible Culprits: 1. Bad Blower Motor. 2. Bad Blower Switch 3. Bad Connection or Bad Wiring 4. Bad Fuse (open) 5. Bad Blower Rela. 6. Bad Resistor (but NOT if the FAN does not work in HIGH speed) Resistor By-passed in High Speed. Note: A DMM can AIDE greatly in the TROUBLESHOOTING Process! I think I have mentioned this--- It takes the Guess Work out of the Process. Gentlemen: A low cost Multimeter SHOULD be in every JEEPER's Tool Box! Thanks goes out to: Jester -- For his INSIGHTFUL POSTS! Let's KEEP on JEEP'IN -- In the NEW YEAR! Let's make 2012 -- A GREAT JEEP YEAR! Cheers! --- JB

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    Re: Iffy Blower Switch.

    *****UPDATE*****

    Well, After finally braving the cold weather, I started trying to pinpoint my Blower motor issues. I directly wired the motor to the battery and it worked fine. Then went through and checked the wiring. All was fine. Then pulled the dash and the HVAC switch controls out. The switch for the fan speed must be going bad or is bad. I messed with the wires at the connection and it started working again. Move the connector harness a little and it would stop. Also, the switch that controls the defrost, vent, floor...etc.... is bad too. It looks like it has gotten really hot and melted.

    So, I guess I am in the market for 2 new switches.

    Where would be the best place to buy them at?

    Thanks guys!
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    Re: Iffy Blower Switch.

    Well Now You KNOW your Fan Motior is Good --- And you would seem to have a Switch Issue. I would be Inclined to Replace BOTH switches --- AND. Check ALL your Wiring Connections to the Switches ( Clean and Tight ) This Should take care of the. Issue. As for WHERE to Buy the Switchs --? Take your Pick --- ANY of the On-Line Jeep guys would be OK! (Morris etc.). GUYS -- Where would you think a good place to BUY Jeep Switchs?? I'm sure these should be FAIRLY easy to obtain?? Comments? -- JB

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    Re: Iffy Blower Switch.

    Quote Originally Posted by Jeeper99 View Post
    *****UPDATE*****

    Well, After finally braving the cold weather, I started trying to pinpoint my Blower motor issues. I directly wired the motor to the battery and it worked fine. Then went through and checked the wiring. All was fine. Then pulled the dash and the HVAC switch controls out. The switch for the fan speed must be going bad or is bad. I messed with the wires at the connection and it started working again. Move the connector harness a little and it would stop. Also, the switch that controls the defrost, vent, floor...etc.... is bad too. It looks like it has gotten really hot and melted.

    So, I guess I am in the market for 2 new switches.

    Where would be the best place to buy them at?

    Thanks guys!
    Rock Auto, Quadratec & Amazon. If this problem happens again replace the motor. When motors fail it will draw more current leading to the melting wires. I don't know what the starting or running current should be so you could check how far off you are but you may be able to take a baseline now and check it again later.
    Dirt and debris along with corrosion are the most common causes for the motor failing.

    Quote Originally Posted by jimbob2001 View Post
    Well Now You KNOW your Fan Motior is Good
    All he knows is the switches and wires are causing the intermittent fan. The motor could be about to fail and drawing enough current to toast bread.

    check this out:http://www.jpmagazine.com/techarticles/electrical/154_0710_jeep_fire_prevention/index.html
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    Re: Iffy Blower Switch.

    What Intermittent FAN? I QUOTE original Poster: " Wired the motor to the Battery and it Worked FINE." End of Quote. Seems pretty CLEAR. Also, In Past Posts on this Board I have stated the Nominal Current Draw For the Blower Motor. How do we Know he did not read that Post --- and did Check out the Motor's Current Draw? We DON'T Know. And IF the Motor was drawing Such HUGE amounts of Current -- Would Not the FUSE have BLOWN First? ( Before we can Toast Bread?) He also Stated: " Then went through and checked the WIRING. All WAS FINE. End of Quote. Am I Missing something here?? If the Original Poster would Like for me to Re-state the Nominal Current for his fan Motor --- I would be glad to do so. (In-rush and steady state) Also, current draw May be measured TWO Ways: 1. Amp Clamp 2. Ammeter in Series with Fan Motor. Original Poster states: He NEEDS a Couple of switches to address this Issue. So -- what is it we are DEBATING HERE? If I may be allowed to Quote: " Never look down on ANYBODY Unless you're helping him up" -- J. Jackson. Well stated! -- JB

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    Re: Iffy Blower Switch.

    My posts are to help the OP. There is no proof the motor is fine and running at expected currents.
    Maybe you need to re read the entire thread.
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    Re: Iffy Blower Switch.

    I havn't checked the amp draw because I don't have a meter. With my busy work schedule, I havn't had time to borrow one from my uncle yet. As soon as I get a reading, I will post it up.

    Thanks again for all the help guys! It's much appreciated!
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