I have a 1987 F250 Diesel N/A with a C6. When I bought the truck a few years ago and the tach never worked even though I changed the sender unit but could never find a dash with a tach. I found a dash with a tach and bought it. Now I finally can see what the engine is turning when I"m asked "how fast". The question I have is after the dash change the volt meter shows it's only charging about 12 volts and the gage shows that's all it's doing. Before the dash change the gage would show a lot more movement in the gage and when I checked with a hand held meter it shows I"m only charging 12 volts idleing or reving the engine. I thought I messed up by not unhooking the batteries so I bought another alternator, a 130 amp alternator which I"ve been running for the last 2 or 3 years.

 

Sounds like either weak as heck batteries, or a weak alternator....

 

Good morning and have a great Friday Wes. Gigger

 

You too Gig....

 

Before the dash change everything was charging fine but after the change it looks like the alternator is only putting out 12 volts. On the back of the dash there is a small, 1" by 2" ic card held on by 2 small screws. I"m wondering if it has something to do with the charging circuit.

 

Funny....Mines doing the SAME crap....

I swapped to a 94 cluster, and had to jumper the ignition/charge wires over....

Well, that worked awesome, until today....

I picked a 1993 Cluster up today, and on the way back to the house, it quit charging......

My voltmeter is only showing ~12volts while the engine is running....

Took the truck into O'Reilly's....A friend of mine works there, and we checked it with a tester....ANOTHER digital tester read ~11.67-12.3v WHILE running....

Swapped the alternators out (Tester said good diodes/low voltage regulator...

Rechecked the NEW alternator/VR....SAME EXACT NUMBERS....WTF...

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Now, I've cleared the playing field....No more of this BS....I have a 1993 Cluster, (My truck is a 1992 model....)

GOtta repin a few things, but otherwise (In a perfect world) if I repin everything correctly, then all the gauges should start working again, and the damned thing should charge correctly.....

OTOH, after I get the repinning, etc done, and it ISN'T charging...WTF could be the issue? New alternator, voltage regulator (Both were changed as of today, as one...) and the battery is ~2 months old....Otherwise, has been running, charging FINE.....

So honestly, W-T-F is left to check/change?

 

Ok, got mine fixed. I ended up pulling the tach from the newer cluster and putting it into the old cluster. The older cluster voltmeter worked fine, the newer cluster voltmeter showed close to 12 volts all the time, running down the road or idling. I now have a 100% working cluster in my 1987 F250. I also have a spare alternator ready for install when needed.