91 Hdj81 dash light issues (1 Viewer)

[ZCissner]

Hello All,
I have had an intermittent rpm issue, if I turn my high beams on, the tach goes to zero.
High beams on=no tachometer
High beams off=tachometer works fine
So the other day I went out to start the truck and both of the turbo lights and the low fluid light is staying on.i have pulled the gauge cluster, checked for loose connections and disconnected the vacuum switches for the boost lights and replaced the fusible links for the Main/Glow.
The issue still persists.
Perhaps the injection pump rpm pickup?

1991 hdj81 full time 4wd H150 5 speed

 

[IanB]

Wonky dash lights are often an early indicator of an alternator on it's way out. Other than that, I'd be checking all my grounds for issues.

 

[ZCissner]

I will check the alternator and get back to you, I replaced it 15 months ago and still have the old one on a shelf and am going to have both tested

 

[ZCissner]

Possibly the culprit, the white wire on the round plug to the alternator is not seated all the way and is broken so it can’t. Will confirm after replacing it.

 

[ZCissner]

Well both alternators tested fine....twice.
The new plug is 3 days out I will update then.

 

[ZCissner]

Well the pigtail has been replaced and no change at all.
Could it be the tachometer pickup on the injection pump? I can’t find a part # for it.
Any ideas on why both boosts lights and the low fluid light would pop on?
Thanks for any help

 

[ZCissner]

Well i unplugged all of the connections for the headlights, and now the tach works perfectly, but both turbo lights and the low oil light are still on.
any ideas?
thank you

 

[IanB]

Well i unplugged all of the connections for the headlights, and now the tach works perfectly, but both turbo lights and the low oil light are still on.
any ideas?
thank you

Wonky electrical often = bad grounds. That's where I'd be focusing my efforts.