So i have finally gotten all my gauges working. Issue is there arent very accurate (to be expected).

My question is how to make them "more" accurate.

Fuel gauge reads 3/4 when full and empty when about 5-6 gallons still left. Replaced sending unit. Same thing. Grounded out gauge, pegs at Full.

Temp gauge reads low. Will sit right above the L mark when fully warmed up.

Oil Pressure reads low. Will site right above the L mark all the time.

Ammeter - No Reading.

When I was rewiring the dash I replaced the stock IVR (which was destroyed) with an electronic IVR from CGFord. Could that be causing everything to read low? Or is it just crappy sending unit tech of the time?

Is there a way to manually adjust the gauges to make them more accurate? Specifically the fuel gauge.

Thanks

 

That voltage regulator will make things read incorrectly since that controls the voltage to the sending units. Low voltage, low readings.

You could adjust your float slightly on the fuel tank sending unit to help compensate. Measure the tank depth and then measure the height of the float compared to the mounting surface. Bend as needed.

 

I've tested outside the tank. Both sending units only register to 3/4.

 

The IVR must not be too far off. If you can ground the wire and it still reads full, then the resistance of the sending unit must be still be just high enough even with float all the way up to make the gauge read 3/4. A slight increase in Voltage would make it read correctly.

I wonder what the actual voltage is suppose to be? What does your read?

 

I'll check when I get home today. How would I increase the voltage? This is a electronic IVR from CG.

https://cgfordparts.com/ufolder/ford...r=C6DZ-10804-E

 

Likely no way to change the IVR itself, unless it has a location to adjust it? Small hole with screw head to turn? I'm guessing it was built for a specific voltage and you can't adjust it. Might have to look at getting a stock version to get one that is closer to correct resistance to a make gauges work correctly.

I'm curious as to what it should be and what it is.

 

I am getting 5.01v off the IVR. There is a small black screw on the back. I've messed with it in and out and it doesnt change the voltage at all.

 

Some of them are in fact adjustable with that screw, or ****. I got a bad batch from one manufacturer where most of them read 2v instead of 5-6! But after a customer called to ask about that, I was able to take them all off the shelf and adjust them at my desk with a battery, some wires and a tiny screw-driver (or was it pliers?) pretty quickly.
With yours reading 5v though, I'd say that's correct. If you were to change it to 6v though, I don't think it would do any harm. Obviously since you said turning the thingy did not change anything, then I guess that's out. But was the unit still attached to the cluster? How are they grounded on these trucks?

The fuel senders are usually "adjustable" too. More like "tweakable" instead though, since they're supposed to be set up properly at the factory and don't have simple screws or anything like that. It's all about bending the float arm and bending the stops. Not sure if yours are exactly the same as mine (what year is your truck?) but the ones in my '71 Bronco were easily tweaked to read perfectly.

First I verified that the water temp and oil press senders were working, then I measured temps and pressures with other mean, and adjusted my original electro-mechanical IVR so that those two gauges read very close to the expected readings. Then I tweaked and fiddled with the fuel sender so it read just how I wanted. Worked great after that.
And by the way, the fuel gauges never read correctly right from the factory. And the brand new-from-Ford senders I bought at the dealer read exactly the same.

To check with an ohm-meter (it's better to check with the gauge, but an ohm-meter gets you in the range) you are looking for 73 ohms empty and 10 ohms full. This puts you in the ballpark so you can mess with it on the gauge.
And since you messed with the cluster, be sure to check, re-check and re-check again that it's somehow getting a good ground bond to the rest of the vehicle.
Does your battery still ground to the body as well as to the engine? If not, you need to add that as well.

Good luck.

Paul

 

Final Update.

Called C&G who sold me the electronic IVR. The screw on the back was put there only for looks to match stock and served no purpose. Voltage was fixed. Picked up a stock non-electronic IVR and got it adjusted and got my fuel gauge working perfect!!!!

Only gauge that does nothing is my ammeter gauge.. not sure what to do about that.. but figure its worthless anyways,.

Thanks for all the help!

 

Wow, a big adjustment! If you were able to get it to go another quarter of a tank full, what did it do to the other gauges?
And the final test will be how it reads when empty. Keep track of miles driven this time. I'd hate to see you out on the road with your thumb out carrying a gas can when the gauge read half a tank!

Good luck. Glad you got it working.

Paul