Fuel Sending Unit
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Junior User
Joined: Mar 2012
Posts: 94
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From: North East Arkansas
Fuel Sending Unit
Fuel gauge was reading incorrect fuel levels so I replaced the fuel sending unit on my 1983 F100 Flareside with a 16 gallon tank. Fuel level is still reading wrong. Noticed Engine temp is also reading wrong. What could it possibly be? Grounded wire, bad connection?
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
D1AZ-10804-A .. ICVR ~ Instrument Cluster Voltage Regulator (Motorcraft GR-513) / Obsolete - Available NOS & from auto parts stores.
Applications: 1971/86 F100/750 & Bronco / 1971/91 Econoline / 1983/85 Ranger / 1984/85 Bronco II // Misc 1971/91 Passenger Cars.
Applications: 1971/86 F100/750 & Bronco / 1971/91 Econoline / 1983/85 Ranger / 1984/85 Bronco II // Misc 1971/91 Passenger Cars.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
I wouldn't buy one of those even if they were available cheaply. They are a poor design and are notorious for changing the voltage and, therefore, the readings for the fuel level, oil pressure, and water temp. I got tired of it and built a replacement that fixes all of the problems of the ICVR. Here's a how to in pictures, with info in the descriptions.
Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
You can buy them on Ebay for ~ $16
http://www.ebay.com/itm/REBUILD-ANY-CONSTANT-VOLTAGE-REGULATOR-DASH-INSTRUMENT-CLUSTER-INTO-SOLID-STATE-/181652658922?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a4b579aea
Jim
http://www.ebay.com/itm/REBUILD-ANY-CONSTANT-VOLTAGE-REGULATOR-DASH-INSTRUMENT-CLUSTER-INTO-SOLID-STATE-/181652658922?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a4b579aea
Jim
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Welcome. And feel free to contact me if you have any issues or questions.
Thanks, Jim. Hadn't seen that. It is a cheaper solution, for sure. But, I worry about what voltage he's setting the regulator to supply. It mentions 6 volts, so that may be the guy I had a lot of discussion with who insisted that the voltage needed to be 6.0 volts.
As you know, the original ICVR's give a pulsing waveform that varies by the load on it, so there is no way that I can imagine to actually determine the true voltage that they were to give. In fact, they weren't designed to give a voltage but wattage since the gauges work by heat. The only way I can find to determine the voltage needed is test it in a real circuit. So, that's what I did and my testing showed that 5.4 volts put all of the gauges I tested, which was several, to where the EVTM says they should be with a precision resistor as the sending unit.
I realize that our gauges don't even have numbers and the sending units appear to vary on their resistance range or calibration. But I would be afraid that the extra 10% would cause the temp gauge to run just hot enough to cause concern with a 190 'stat. And the fuel gauge might not get to E before you ran out. I'd rather have my gauges showing what Ford intended. But, if someone were to try this guy's ICVR then maybe we could discontinue making our own.
You can buy them on Ebay for ~ $16
Rebuild Any Constant Voltage Regulator Dash Instrument Cluster Into Solid State | eBay
Jim
Rebuild Any Constant Voltage Regulator Dash Instrument Cluster Into Solid State | eBay
Jim
As you know, the original ICVR's give a pulsing waveform that varies by the load on it, so there is no way that I can imagine to actually determine the true voltage that they were to give. In fact, they weren't designed to give a voltage but wattage since the gauges work by heat. The only way I can find to determine the voltage needed is test it in a real circuit. So, that's what I did and my testing showed that 5.4 volts put all of the gauges I tested, which was several, to where the EVTM says they should be with a precision resistor as the sending unit.
I realize that our gauges don't even have numbers and the sending units appear to vary on their resistance range or calibration. But I would be afraid that the extra 10% would cause the temp gauge to run just hot enough to cause concern with a 190 'stat. And the fuel gauge might not get to E before you ran out. I'd rather have my gauges showing what Ford intended. But, if someone were to try this guy's ICVR then maybe we could discontinue making our own.
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Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
I was looking at the Ebay VR to see if it had an external adjustment screw to change the output voltage. I could not tell by the photos. It looks like he will set the voltage to what you want.
It still really amazes me that the Ford idea of a variable duty cycle square wave based on load even works giving the wide resistance changes of the 3 parallel circuits down stream of the VR.
The water temp and oil press would be stable after the engine warmed up, but the fuel gauge resistance changes from 80 ohm empty tank - to 10 ohms full tank.
It would seem the circuit resistance could range from 10 ohms to say 45 ohm depending on oil press / water temp (thermostat range).
What resistor value did you use to come up with the 5.4 volts?
Jim
It still really amazes me that the Ford idea of a variable duty cycle square wave based on load even works giving the wide resistance changes of the 3 parallel circuits down stream of the VR.
The water temp and oil press would be stable after the engine warmed up, but the fuel gauge resistance changes from 80 ohm empty tank - to 10 ohms full tank.
It would seem the circuit resistance could range from 10 ohms to say 45 ohm depending on oil press / water temp (thermostat range).
What resistor value did you use to come up with the 5.4 volts?
Jim
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Brett Foote
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Yes, it is hard to believe the Ford ICVR ever worked. The key is in the fact that the gauges work from heat. But, when you throw an 8.5 ohm resistor between the ICVR and the battery and impose a changing load behind it the mind boggles mind. I'm sure someone got a huge award for figuring out how to use the temp-sensitive gauges with such a simple circuit.
As for the senders, with the range of resistance from 10 at full scale to 72 ohms at the low end the parallel resistance can range from 3.33 ohms to 24 ohms. That puts a lot of current through that 8.5 ohm resistor, so there's a fair amount of heat being generated.
My tests were documented here, but I used 10, 22, and 75 ohm wire-wound resistors to simulate the senders, which the EVTM says can range from 10 to 73 ohms. And somewhere in the Ford documentation it says 22 ohms represents mid-scale. So I tested first with a known-good ICVR and then substituted a true voltage regulator and tweaked the voltage until I got the same readings as with the EVTM. That ranged from 5.37 to 5.47 volts across several gauge sets, so I rounded that to 5.4 volts. Which is interesting since the EVTM says that the output of the ICVR is "5.0 volts average". Yeah, sure.
As for the senders, with the range of resistance from 10 at full scale to 72 ohms at the low end the parallel resistance can range from 3.33 ohms to 24 ohms. That puts a lot of current through that 8.5 ohm resistor, so there's a fair amount of heat being generated.
My tests were documented here, but I used 10, 22, and 75 ohm wire-wound resistors to simulate the senders, which the EVTM says can range from 10 to 73 ohms. And somewhere in the Ford documentation it says 22 ohms represents mid-scale. So I tested first with a known-good ICVR and then substituted a true voltage regulator and tweaked the voltage until I got the same readings as with the EVTM. That ranged from 5.37 to 5.47 volts across several gauge sets, so I rounded that to 5.4 volts. Which is interesting since the EVTM says that the output of the ICVR is "5.0 volts average". Yeah, sure.
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