hi guys i have a 1971 ford 3/4 ton truck i just replaced the fuel sending unit in the tank and it was working the gauge and the sending unit and the temperature gauge was also working now i dont have temperature or fuel gauge working any ideas would be greatly appreciated thank you

 

The common element in your problem is the CVR- constant voltage regulator- which is a small item in the dashboard that keeps swings in alternator voltage from reaching the gauges. The guys will be in soon to tell you how to get at it for your particular truck.

 

It's probably important for you to let us know whether your dash has indicator lights or gauges.

IIRC, the CVR works with either instrument cluster, and it's the prime suspect.

Also, do you have dual tanks? If so, there's a tank selector switch that feeds the signal from either tank sender to the sole fuel gauge.

It's possible (but not likely) that you have two problems. If R&R -ing the regulator fixes both problems, you've got it licked; otherwise, you'll need to do some more sleuthing.

 

hi guys thank you for the replies i appreciate it it has the gauges in my dash

how do i test the cvr and how much is a new cvr thank you

 

You'd likely need an electronics lab to see if the thing's still in spec. Dunno if I've ever heard of a test for it.

LMCTrucks.com has it for $50. I was looking at it today... I need one too

EDIT:
Page 79, item 34 for years '67-'69 $30
Page 79, item 35 for years '71-'72 $50

That lets me out, I need the one for 1970! (sheesh!)

 

well found location of constant voltage regulator removed 1 screw holding onto the back of the instrument cluster and bingo turned the key gauges work thank you everyone for the help

 

Yeah, I pulled mine out as well. Turns out it looks like the '71-'72 part.

Had to pick my son up from High School before I could get the instrument cluster reinstalled. When he noticed the big gap in the dashboard, he said "Ok, THAT's casual!" I then explained to him that there's a lot of stuff that you don't really need in order for the truck to run.

It made me wonder - Will the new trucks run if you remove the instrument cluster, or does the computer freak out and choke up?

 

yeah you are lucky . I thought that was my problem, but none of my gauges work , so I have a big electrical headache, glad you got yours fixed.

 

I own a '67 F600 330ci and my tachometer, fuel gague, speedometer, alternator gauge and oil temp gauge all work. Unfortunately, my temp gauge is the only faulty one. Any ideas on how to troubleshoot? Thanks!

 

Remove the temp wire from it engine sending unit and touch it to ground for just a few seconds, if the dash gauge is working it will go all the way to hot
when grounded. Best to have a helper so you can watch the gauge..

So replace sender if gauge is good.
Orich