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My gas gauge is pretty inaccurate on my 66 F100. I figured there's probably an issue with the constant Voltage Module.
I replaced it, but not only did it get worse, my temperature gauge started reading about 30 degrees lower. This makes no sense to me since it seems like the module only connects to the gas gauge. Also, if I pressed on one of the terminals, the temperature reading would go up.
All very odd, I figure the new module is defective, because a thermocouple at the temperature sensor location reads close to the temperature I get with the old module.
Anyone have any experience with this? I'd like to understand what is happening here.
Put your old module back on, or else an NOS one instead of the Chinese repops out there. Adjust the fuel sending unit in your tank, you should be able to find the thread on doing this via the search function.
My gas gauge is pretty inaccurate on my 66 F100. I figured there's probably an issue with the constant Voltage Module.
I replaced it, but not only did it get worse, my temperature gauge started reading about 30 degrees lower. This makes no sense to me since it seems like the module only connects to the gas gauge. Also, if I pressed on one of the terminals, the temperature reading would go up.
All very odd, I figure the new module is defective, because a thermocouple at the temperature sensor location reads close to the temperature I get with the old module.
Anyone have any experience with this? I'd like to understand what is happening here.
After going through 3 or 4 IVRs I went on Ebay and purchased a 12v-6v voltage reducer for $10. It had one hot wire(red) and one ground wire(black) in and the same going out. Attach the grounds to the brace behind the instrument cluster and the +'s and you are finished. Mine has an output of 5.9 volts. Now the gauges work as they should.
After going through 3 or 4 IVRs I went on Ebay and purchased a 12v-6v voltage reducer for $10. It had one hot wire(red) and one ground wire(black) in and the same going out. Attach the grounds to the brace behind the instrument cluster and the +'s and you are finished. Mine has an output of 5.9 volts. Now the gauges work as they should.
I'm happy that worked for you, but I'm surprised. I considered doing what you did, but I thought that if it were an option the automakers would have done it.
Eric.
So it's just a 12v to 6v converter? You can do that with an LM317 for $1
Your OE device is a electo-thermal-mechanical device, similar to a turn signal flasher, except your ivr is designed to output ~5-6V.
You can use a semiconductor device, but I would probably go for an LM338 over the LM317 for current head room.
Bills right the ICVR runs all the gauges. These King Seeley gauges are so sensitive to voltage that 1/10 of a volt will make a difference in the gauge reading. To be accurate the gauges need an input voltage as close to 5 volts as possible. A shop manual from the late 60's or early 70's will go into great detail on how to test and trouble shoot those gauges.
Here are a couple of pictures of a gas gauge. The first is a cold gauge the second is the same gauge with an ohm meter connected to it, as you can see the tiny amount of voltage applied by the ohm meter moved the needle.
I replaced it, but not only did it get worse, my temperature gauge started reading about 30 degrees lower. This makes no sense to me since it seems like the module only connects to the gas gauge. Also, if I pressed on one of the terminals, the temperature reading would go up.
When you press on the terminals will the gas gauge reading change at all? Also is the temp reading rising to the proper level when you press on it?
I bought a chinese repop for a mustang and it worked fine. Like stated above you can check the voltage output to make sure its operating correctly.
So what's the proper voltage for the gauges? 5v or 6v?
All of the King Seeley type gauges that Ford used in everything for decades are nominal 5 volts. Here are a couple of pages from the 71 shop manual.
Your system does not use a printed circuit so it won't have a radio choke or resistor in the circuit.
You can use the original electro mechanical ICVR or the solid state replacements. I prefer the solid state type because they put out a constant 5 to 5.1 volts. But they are made where English isn't their first language so test it before you install it. Most of the problems with these gauges are caused by bad senders and don't count on a new sender being any better than the old one. I have a shelf full of oil pressure senders I bought before I found one that gave the correct reading. Shop manuals are your friend you need a 50 year old book to work on a 50 year old vehicle.
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