Fuel gauge/tachometer

[Junior9009]

The fuel gauge in my 89 R model doesn't work. It's always showing empty. Also my tach will drop out from time to time then come back. Where is a good place to start looking? Where is the ground for both of these?

[alex g]

Your fuel gauge could be sending unit in tank or gauge. I'd start by checking to see if there's power at either end. As far as your tach goes it's run of a cable and the tach itself is probably wore out.

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[39 Baby Mack]

Greg

If you ground the wire on the sending unit (the one on the terminal) with the key on the fuel gauge should go all the way to full. If it does that should tell you that the gauge and wiring are allright. Also check to make sure that the ground wire to the tank is good (the wire going from the chassis to the sending unit attached to one of the mounting screws of the sender)

If all that checks out it's the sending unit.

As for the tach it could also be the cable itself. I know that sounds strange how would it work and stop and then start working again.

A lot of the original Mack cables came with different slip on ends for the drive end. This allowed them to be used as RPM cables or speedometer cables by length. All you had to do was use the right tip on the drive end. These were made to slip into the cable and the cable core was swedged sguare so the tip could drive it. I've seen them wear there and slip in the lower tip. This would cause the tach to act up.

I personally never liked them and used to make my own cables using Stewart Warner or S.S. White parts. That way both tips were swedged to the core.

Ron

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[Back In Black Pulling]

The little tab could be broke off worn on the shaft between pump and drive. had that prob yesterday , took drive apart and tack welded it.

Assuming it is same on your motor

or does it have electric tach

[Timmyb]

Are you sure it's not an electric tachometer? The one in my kw is electric and runs off the alternator. When it cuts out it usually means alternator is on its way out.

[KoryBorah]

Is the Fuel Gauge and Tachometer, both are same?

As per my knowledge the Fuel Gauge is used to measure level and the tachometer is used to measure the RPM or velocity of  a rotating part?

What application Tachometer does have and what are its specifications?

 

printed circuit board assembly

Edited March 11, 2016 by KoryBorah

[Junior9009]

My tach is electronic. I was messing with the telescopic steering wheel the other day and everytime I would push the column towards the dash with the truck idling the tach would drop out and come back. I imagine I have a short somewhere?