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The test light on the sending unit side gave me a steady light with the test light.
I switched out the voltage regulator on the back of the speedo and I get the same reading.
(speedo was just rebuilt, I don't recall if they checked the gauges...
I did check the fuel gauge by using jumpers and it goes to full.
I did an ohm check on the sendeing unit and it reads ok.
I pulled the sender unit and tried to get the fuel gauge to react to different settings, and it stayed on full.
Is there a check I can do for the 'new voltage' regulator?
thanks,
rtc
Is there a check I can do for the voltage regulator.
First the shop manuals for middle 60's trucks are lacking in info on checking these gauges. The late 60's early 70's manuals are much more specific on how to check them.
All the gauges are essentially the same they just have different faces to depict what they are measuring. The senders do basically the same thing. All the gauges and senders work on 10 ohm high reading and 80 ohm low reading.
The way to check the ICVR and the gauge at the same time is to remove the wire from the sender and connect a 10 ohm resistor to ground, the gauge should go to the full mark. To check the low reading connect a 73 ohm resistor to ground and the gauge should read at the low mark. 75 ohm resistors are easier to find than 73's and will work just fine.
To isolate a bad ICVR from a bad gauge run that test on both gauges. If one gauge reads correctly and the other does not then you know the gauge is at fault, if they both read wrong you know the ICVR is at fault. And naturally if they both read correctly then the sender is at fault. These gauges are extremely sensitive to the voltage they are receiving from the ICVR an ICVR that is off by 1 volt will check good with a test light or a volt meter but will cause the gauges to be inaccurate. The ohm test is the only way to know for sure that gauges and ICVR are happy together.
The fuel gauge sender is the only one that can be accurately checked with an ohm meter. You have to remove it from the tank and check the resistance it should be somewhere in the range of 8-12 ohms full and 60-86 empty. The one in my truck reads 13 ohms full and 73 ohms empty. Close enough..
This is a picture of a bench test using a 10 ohm 3 watt resistor and a solid state ICVR with a fuel gauge. The solid state ICVR's put out a more constant voltage than the electro mechanical ones but the gauges will react slower with them because they don't get that 12 volt boost that they get with the mechanical one when they are energized.
First the shop manuals for middle 60's trucks are lacking in info on checking these gauges. The late 60's early 70's manuals are much more specific on how to check them.
All the gauges are essentially the same they just have different faces to depict what they are measuring. The senders do basically the same thing. All the gauges and senders work on 10 ohm high reading and 80 ohm low reading.
The way to check the ICVR and the gauge at the same time is to remove the wire from the sender and connect a 10 ohm resistor to ground, the gauge should go to the full mark. To check the low reading connect a 73 ohm resistor to ground and the gauge should read at the low mark. 75 ohm resistors are easier to find than 73's and will work just fine.
To isolate a bad ICVR from a bad gauge run that test on both gauges. If one gauge reads correctly and the other does not then you know the gauge is at fault, if they both read wrong you know the ICVR is at fault. And naturally if they both read correctly then the sender is at fault. These gauges are extremely sensitive to the voltage they are receiving from the ICVR an ICVR that is off by 1 volt will check good with a test light or a volt meter but will cause the gauges to be inaccurate. The ohm test is the only way to know for sure that gauges and ICVR are happy together.
The fuel gauge sender is the only one that can be accurately checked with an ohm meter. You have to remove it from the tank and check the resistance it should be somewhere in the range of 8-12 ohms full and 60-86 empty. The one in my truck reads 13 ohms full and 73 ohms empty. Close enough..
This is a picture of a bench test using a 10 ohm 3 watt resistor and a solid state ICVR with a fuel gauge. The solid state ICVR's put out a more constant voltage than the electro mechanical ones but the gauges will react slower with them because they don't get that 12 volt boost that they get with the mechanical one when they are energized.
Wow!
It's brain stretching time!
That's a whole new world to m, but that's what I signed up for.
#NewbieButWillingToLearn
So I haven't tried the ohm check yet...out of my experience level...but I have someone here that may help.
In the meantime...
This is what I have done:
Switched out the voltage regulator for a new one.
Grounded out the power wire from the sending unit and the fuel gauge went to full.
I did buy a new sending unit and hooked it up without putting it in the tank...the empty level read correctly and the full level read half.
I had only a few gallons left in the tank (I siphoned out approximately 15 gallons for something else I was doing, checked the fuel gauge and it still read half
At the moment I'm still trying to find resistors I can get locally.
If anything pops out... as something to try, I'd appreciate the links and hints.
Just a kind of FYI, ICVR use a mechanical form of voltage regulation, inside is a bi-metallic strip that heats up and makes and breaks contact (ON/OFF) every couple seconds or whatever. So when trying to measure output with a digital voltmeter it will just display gibberish.
The regulation will average down 12 volts nominal to maybe ~ 6 or 7 volts. The gauges are analog and damped, so are very sluggish to respond to voltage changes, they end up more or less averaged and more or less accurate when working correctly.
