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?

 

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.

 

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

 

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

 

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

 

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?

 

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).

 

well my ac doesn't work, but even when my ac worked several years ago, the tach didnt...