problems with my gauge

[teddyyyy]

I recently bought my 72 F250 with all the gauges non-working. but the turn signal blinkers on the dash does work.

today I tried to fix it. and found that the speedometer cable coming from the output of transmission case to the back of gauge cluster was disconnected. that's an easy job, I connected it, now the speedometer does turn, but very not accurate: it jumps sporadically across a range of about 20mph, and no matter how fast I go, it maxes out at 35mph.

I was pretty surprised to find so many cables behind the gauge, it's all crowded together, very difficult to separate out, let alone figuring out which wire is for which. in this case, what would be the best approach to diagnose and fix the gauges?

thanks!

[hazelnut]

Can't help with the other gauges but can with the speedometer. The problem is the cable is dry inside and the cable can't spin freely because of friction causeing the speedometer to jump around. If you want to fix it pull the whole cable out of the truck and then pull the cable out of the case. Rub the whole cable with graphite, Then put some inside the casing then slide the cable back inside. If the cable don't spin freely by spinning between your fingers then repeat. That should lube it up and make the speedometer work again.

[68RGR]

On the gauges - There is a small voltage regulator mounted on the rear of the dash cluster. It's on the driver's end of the back of the cluster.

The regulator supplies something around 6 volts to the gauges. Without it, the gauges won't work. Not sure if this includes the ammeter because it might not need that voltage.

Anyhow, the regulator is really more of a vibrator that makes and breaks the connection rapidly so that the effective voltage is reduced from 12 volts to around 6 volts. I think the term for it is IPVR - Or, instrument panel voltage regulator.

It might not be easy but you need to verify the operation of the regulator by checking the voltage to the gauges with the ignition switch in the "ON" position.

[hillcountryflt]

New IPVRs are available. NAPA carries them as well as on Ebay.
As to the speedo, make sure it spins free in the console as well. I purchased a used unit off of ebay as my instruments had quit working, except for the speedo. But the speedometer would not turn in the new unit. Just swapped out the one speedometer unit from my original unit to it.
While you have the console, I would suggest getting a polishing cloth (you know the stuff that comes in a can and you tear off pieces) and pull the bulbs and clean the contacts. At $1.99 each, I replaced each of my six light bulbs with new bulbs/carriers from NAPA.