Tac, goes nuts

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Apr 14, 2006 | 07:51 AM

scurbiedog

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From: B.F.E.

Tac, goes nuts

Has anyone ever had a tac, bounce? Mine has been every now and then but , the motor does'nt rev up or anything its just the tac, any ideas?

Apr 14, 2006 | 08:07 AM

BillyBob69

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Joined: Jul 2003

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From: Wheatland, Mo

Loose connection? Usually the initial charge when power is applied makes the tach sweep. Kind of an intilization. Loose connection could be dropping for a split second causing to to lose and regain power.

Or maybe the tach itself.....or....etc.

I am sure someone else will chime in with other ideas too.

Apr 14, 2006 | 10:55 AM

AvalancheChaser

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Joined: Mar 2006

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I had that problem a few years ago, and it was the tach itself. Like bb69 said...probably bad connection or bad tach.

Apr 14, 2006 | 03:38 PM

JLMoreno911

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My tach doesnt work either...does anyone have a schematic of the wiring for the tach...

Apr 14, 2006 | 04:15 PM

greystreak92

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From: Gateway to the West

What model year truck(s) are we dealing with? The wiring for the tach changed quite a bit over the years.

Apr 14, 2006 | 04:22 PM

JLMoreno911

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I have a 1991 Bronco 351 auto, when I turn the key to on with engine still off the tach goes to about 3300 rpm, once the engine in running it stays there untill I accellerate then it may go up to 4500 depending how much gas I give it.

Also my tach goes up to 6000 rpm but does not show any red...what is the redline for a '91 bronco?

Apr 14, 2006 | 05:18 PM

greystreak92

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From: Gateway to the West

Smallblocks redline at about 4k. The wiring for your 91 is a TAN/YELLOW and a BLACK/YELLOW wire along with a power feed RED/YELLOW that is common to several other dashboard components. The TAN/YELLOW originates at the ignition module and the BLACK/YELLOW originates at the A/C clutch resistor diode. If the A/C clutch has a problem chances are the tach may be affected. (NOTE: the BLACK/YELLOW wire is NOT USED on trucks equipped with the 4.9L (300 I-6).