 Defrost fan won't turn off |
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| jmargush |
 Sep 8 2014, 07:21 PM
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#1
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Member  Group: Members Posts: 460 Joined: 8-June 04 From: Goshen, IN Member No.: 2,176  |
Got home from the autox yesterday and noticed something running when I shut the car off. Thought it might be fuel pump but it wasn't. Instead it was the defrost fan behind the fuel tank.
I tried pulling all the fuses and it never shut off. Any suggestions on where or what to look for? |
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Replies(1 - 9)
| Dave_Darling |
Sep 8 2014, 11:02 PM
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#2
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
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The relay may be stuck somehow. Certainly unplugging the relay should stop the blower.
The relay gets un-switched power on terminal #30. If the relay sticks, connecting 30 to 87, it will send power to the fan no matter if the ignition is on or not. The switching should happen when the ignition is on and when the heater lever is up all the way. The former provides power to the coil in the relay, the latter provides the ground. Even if the wire to the heater lever shorts to ground, turning the key off should still stop the relay from connecting 30 and 87. So that means either the relay is faulty, or something is connected incorrectly. Swap the relay for one of the headlight relays. If the light doesn't work (or doesn't stop going up and down!) and the blower works correctly, you've found the problem. --DD |
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| jmargush |
Sep 9 2014, 04:11 AM
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#3
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Member Group: Members Posts: 460 Joined: 8-June 04 From: Goshen, IN Member No.: 2,176 |
You mention the lever being up
Are you refering to the one on the floor? If so doesn't that just control the blower motor back in the engine compartment? |
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| BeatNavy |
Sep 9 2014, 05:01 AM
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#4
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Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region
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QUOTE(jmargush @ Sep 9 2014, 06:11 AM)  You mention the lever being up Are you refering to the one on the floor? If so doesn't that just control the blower motor back in the engine compartment? Yes, the lever on the floor. Pulling it up opens the flapper boxes to allow heat from the exchangers to pass through the longs and into the passenger compartment. As Dave said pull that lever up high enough and it grounds the blower motor circuit so the blower motor gets power and runs (assuming the relay is working correctly). |
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| jmargush |
Sep 9 2014, 05:45 AM
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#5
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Member Group: Members Posts: 460 Joined: 8-June 04 From: Goshen, IN Member No.: 2,176 |
Does that lever also control the motor up front by the gas tank? Cause that is the one that is staying on
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| bdstone914 |
Sep 9 2014, 06:03 AM
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#6
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bdstone914 Group: Members Posts: 4,537 Joined: 8-November 03 From: Riverside CA Member No.: 1,319 |
The heater lever does not control the defrost fan. It is probably the relay as suggested.
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| Dave_Darling |
Sep 9 2014, 09:23 AM
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#7
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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Shoot, you did say "behind the gas tank". I should have realized you meant the fresh air fan. My advice was all intended for the heater blower, which is what I thought of when you said "defrost fan". Sorry about that.
I'm not sure what feeds the fresh air fan, except that one of the relays on top of the fuse panel sends switched power to it. And to lots of other systems as well. If you can figure out what else gets powered from that, check if those things are on or not. --DD |
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| jmargush |
Sep 9 2014, 12:10 PM
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#8
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Member Group: Members Posts: 460 Joined: 8-June 04 From: Goshen, IN Member No.: 2,176 |
Thanks
I'll check that relay board |
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| rhodyguy |
Sep 9 2014, 03:11 PM
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#9
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,093 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
did you try moving the fresh air control sliders?
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| partwerks |
Sep 9 2014, 09:24 PM
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#10
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Senior Member Group: Members Posts: 1,593 Joined: 7-September 06 From: Grand Island, NE Member No.: 6,787 |
I'd pull the ask tray, and see what's going on with that.
On mine, somewhere in it's past, the bottom contact has gotten pushed down, and looses contact with the top one. Hard to get in there and pull it up, but may be able to do it when getting the conversion done, and get better access. |
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