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Mo*or Mo**h
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1,730 Posts
Discussion Starter · #1 ·
My FTU is faulty, I'm presuming.

Most folks have had a problem with the FTU causing the fans to run with the engine off and running the battery down.

Mine is acting differently. My issue is the Rad Fan never comes on unless the AC is turned on too. Then, both fans run properly in high/low mode as necessary.

The odd part is that the battery is being drained by this Fan activity even with the engine running. It can get to the point the car dies completely from lack of battery power, very much like when the alternator fails to recharge the battery. As long as I don't run the AC, no problem. It only does this when the AC is running.

As soon as I turn off the AC, both fans quit and the battery begins to recharge normally. It's weird. I put a meter on the battery and watched it go from 14.0V to under 12.0V while the fans ran, then turned off the AC and watched it rise back to 14.0V again, all while idling in the driveway.

I'm assuming the FTC is at fault here, but it's possible the FCU (Fan Control Unit) is the issue, or both.

Anyone seen anything like this before?
 

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489,000 km's stil going
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1,016 Posts
That sounds more like some kind of short in the AC circuit. In order to drain your battery. You could try pulling your fuse for the fan in the little black box on your drivers side fender (I think the third from the right or second one - it's written there). Then see if you get the same result - a voltage drop.

I have driven all winter with no fans at all. As long as i'm not at a dead stop for over ten minutes in heat the engine temp is fine. When I got the car the passenger fan came on at night. (That was my very first forum post here). My solution was to pull out the plug on the fan and just run with the condenser fan which worked fine for several years. Then that one failed last summer driving to the US. (Long border wait caused it to almost overheat).

I'm going to follow some of the threads in this forum this spring and fix it properly now that it's warm here. There are some really good ideas when you search that subject here.
 

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Mo*or Mo**h
Joined
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1,730 Posts
Discussion Starter · #3 ·
I have already done all the fuse testing, one at a time to isolate the voltage drain. Turned out that was the antenna motor. It had started a grinding noise as it rose (but, quiet going down) a week or so ago. Then, it just stopped going up altogether. The next day, my nearly brand new Red Top was completely dead (no instrument cluster lights even). While fixing that, I decided to do the Rad Fan (since that is typically what ends up running the battery down like that) and that's when I ran into that situation with it running the battery down only when AC ran, even with engine running.

And, have also gone most the winter without the Rad Fan working normally. Didn't need it to keep cool at all until AC season came.
 
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