Tachometer Stays at 500 RPM after engine Shut Off

[DMcV]

Seasons Greetings All...

I've been watching and reading but haven't posted lately.

But I hope someone may have an answer to my problem.

Did a search but saw nothing...

2000 F350 7.3 Super Duty Dually LB 90k miles

Problem...
The tachometer will stay at 500 RPM after ignition turned off / engine off.
I am sure there is a current draw as it will jump back to zero if I turn the ignition key on but no to start.
It will start right up again...no problems.. and no erratic movement within the tach while under way.
All seems normal except the needle not returning to '0' (zero)

If left for a few days it will be a strain for the batteries to get it started....new batteries just 6 months ago.

Anyone have some input what might have brought this on or where to look?

Thanks in advance

DMcV

 

[79jasper]

With key off, doors closed, start pulling fuses one at a time and put it back in, see if/when the tach drips. You could maybe measure current draw across the terminals.

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[DMcV]

Thanks...will try that soon on a dry day

 

[79jasper]

Can't say I've heard of that either.
No other malfunctions?
Could be the gem module going bad also.
May even try swapping some of the relays around. One could be sticking a little.

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[DMcV]

It has been suggested that it may be the cluster.

However... the symptoms of a bad cluster involves way more than what I have going on.

I will keep testing and see if I find anything.

Islander

 

[OLDBULL8]

The tach is powered out of the GEM, if it has ever got wet from a windshield leak that could be the problem.