Heater kills tach

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Jul 10, 2009 | 10:42 AM

kenpobuck

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Cargo Master

Joined: Mar 2006

Posts: 2,789

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From: Sand GAp, KY

Heater kills tach

It was raining this morning which always fogs up the windshield. I turned on the blower fan and my tach dropped down to about 300 rmp, no matter how much fuel I gave it it didn't move till I turned off the fan. The volt meter (after market) didn't move just the tach. No other accessory does this ( turning on the headlights moves it a little). Any help would be great. I know the body and electrical system is a Bronco but they should be almost identical to the rest of the F series.

Jul 10, 2009 | 04:41 PM

Dave Sponaugle

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Joined: Nov 2003

Posts: 21,285

Likes: 15

From: Nutter Fort, WV

Sounds like a ground issue to me.

Either the dash to body, or the body to chassis, or the body to battery.

Jul 10, 2009 | 04:52 PM

kenpobuck

Thread Starter

Cargo Master

Joined: Mar 2006

Posts: 2,789

Likes: 5

From: Sand GAp, KY

Thanks Dave, I will check all those in the morning. I hope it is that simple lol.

Jul 13, 2009 | 09:15 AM

gov2mod

Tuned

Joined: Jul 2004

Posts: 476

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From: Delaware

My 87 F250 6.9 does the same thing when I turn on the headlights. It's been like that for years.

Jul 13, 2009 | 10:58 PM

Dave Sponaugle

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Joined: Nov 2003

Posts: 21,285

Likes: 15

From: Nutter Fort, WV

On the 87 I think I would start looking at the insturment cluster plug.
My gauges were doing funny things, unplugging and replugging the insturment cluster connection fixed it.

Jul 14, 2009 | 06:23 AM

gov2mod

Tuned

Joined: Jul 2004

Posts: 476

Likes: 5

From: Delaware

I'll try it and see if it works. It's way down on my daily list of 1001 projects though which no matter how many a day I complete the quantity on that list never seems to go down. However, I'm never bored.

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