Fuel and Temp Guages, Not the same old symptoms....

[imabigbangkindaguy]

OK, Last night I went for a drive in the crisp Texas evening, and discovered that my fuel and temp gauges were not working... again...

I thought I had this sorted out!! About two weeks ago I put in a new gauge cluster, and they worked just fine!!

About 5 minutes into the drive, the gauges came to life. At stop lights, i noticed that the gauge cluster bulbs would fluctuate, get dimmer, then when I would go, the bulbs would go back to a brighter normal.

This is the new symptom; My Fuel and Temp gauges were doing the same thing!! At the stop light they would die, or drop low, then when i would accelerate they would come back up. After about 20 minutes of driving around, the cruiser was warmed up, and I experienced neither symptom again.

Has anyone else with the Fuel and Temp gauge problem noticed this? Could this be an underlying issue with the generator or voltage regulator?? Or bad connections, which have been checked, re-checked, cleaned and re-cleaned.

Tell me what you think guys...

Another question is does everyone elses fuel sender wires run on the outside, underneath their cab, or is mine a hack job by a PO?

 

[bsmith123]

prob

i think this post rings a bell---can u put up a link to your past trouble that may help

took a quik look at the 76 schematic on Coolermans schematics site

Have a look at the terminal from your ignition switch into the fuse box

also

On the output side of the fuse box power for the lights come via the headlight sw

power for the gauges comes via the heater fuse

on the input side these wires become common at a splice see circled bit)

if the wire came loose at this splice it would affect both your dash back lights and the meters (maybe other things as well) and as long as the ignition wiring side of it was still good --keep running


you could try running a

 

[65swb45]

What are your idle rpms, and what is your voltage at idle?

 

[bikersmurf]

Sounds a lot like a grounding issue. Check out this thread:
https://forum.ih8mud.com/40-55-series-tech/415151-never-underestimate-importance-ground.html

I've seen gauges do weird things when the wiring harness ground under the gas tank wasn't connected.

 

[bikersmurf]

The fuel sender wires usually run across the top the top of the cover and in through a small hole in the cover.

 

[Rocky_LC]

The fuel and temp guages get power from the same source, and are linked together, IIRC.

Rocky

 

[Pin_Head]

The dash lights are on the head light fuse, while the gauges run off the heater fuse, so if they flicker in common, the problem is up stream from the fuse block. The dimming at idle is typical behavior, as the alternator cannot put out full voltage at idle. The gauges have a separate voltage regulator built in to the fuel gauge meter which is there to prevent this fluctuation at low engine speeds. Maybe it isn't working.

 

[imabigbangkindaguy]

What are your idle rpms, and what is your voltage at idle?

Warmed up, I am at about 500 RPM w/ out choke at idle. Cold, wont run, except with choke, and then about 1k. I mean it wont run this time of year, the other 10 months here in Texas, I never use the choke.

My voltage at idle stays dead middle, when warm.
Slightly toward -30 when cold, and pings toward -30 when turn signal indicators are on, warm or cold.

The fuel sender wires usually run across the top the top of the cover and in through a small hole in the cover.

Yes, that is how mine are set up currently, I have read and re-read that article... words to live by with any classic rig you work on yourself, Thanks, I will re-check all grounds this coming weekend.

The dash lights are on the head light fuse, while the gauges run off the heater fuse, so if they flicker in common, the problem is up stream from the fuse block. The dimming at idle is typical behavior, as the alternator cannot put out full voltage at idle. The gauges have a separate voltage regulator built in to the fuel gauge meter which is there to prevent this fluctuation at low engine speeds. Maybe it isn't working.

I would think this maybe, but I just want to be optomistic about the newer cluster I installed, and hope that it works. When I installed it, I tested the voltage each gauge was recieving, and all was correct as to what I have read, 12v coming into fuel gauge, fluctuating reading going from fuel to temp... and a fluctuating reading at the temp gauge.
It was my impression that the dimming lights were typical, I recall last winter, the lights doing the same thing.

i think this post rings a bell---can u put up a link to your past trouble that may help

took a quik look at the 76 schematic on Coolermans schematics site

Have a look at the terminal from your ignition switch into the fuse box

also

On the output side of the fuse box power for the lights come via the headlight sw

power for the gauges comes via the heater fuse

on the input side these wires become common at a splice see circled bit)

if the wire came loose at this splice it would affect both your dash back lights and the meters (maybe other things as well) and as long as the ignition wiring side of it was still good --keep running


you could try running a

Here is my original post,
https://forum.ih8mud.com/40-55-series-tech/403290-fuel-temp-gauge-problems.html

Great post with the wiring, that might be something to try, if all else fails.

Thanks for the responses guys, any help is appreciated!

 

[bikersmurf]

It sounds like you're talking about the amp meter when you talk about -30/+30.

To explain in simplified terms, amps = quantity of electricity moving, and volts = the pressure making them move.

A voltmeter or a multimeter with a volt setting may help to find the route of the problem.
Good luck.


You might also benefit from adjusting your idle speed up to +/- 650 rpm if the problem relates to alternator output.

 

[65swb45]

You might also benefit from adjusting your idle speed up to +/- 650 rpm if the problem relates to alternator output.

What he said .....

x2.

 

[Pin_Head]

I tested the voltage each gauge was recieving, and all was correct as to what I have read, 12v coming into fuel gauge, fluctuating reading going from fuel to temp... and a fluctuating reading at the temp gauge.

The fuel gauge has a built in voltage regulator that takes the chassis voltage that fluctuates between 12 an 14V and steps it down to a constant 10V to run the gauges so that they don't fluctuate with the chassis voltage. If your gauges move with the lights, then the gauge voltage regulator isn't working. It is a mechanical type, so chances are that the points are stuck. If the voltage is not regulated, the guages will also read high.

It is not a big deal if it doesn't work. You will get used to it.

 

[imabigbangkindaguy]

It sounds like you're talking about the amp meter when you talk about -30/+30.

To explain in simplified terms, amps = quantity of electricity moving, and volts = the pressure making them move.

A voltmeter or a multimeter with a volt setting may help to find the route of the problem.
Good luck.


You might also benefit from adjusting your idle speed up to +/- 650 rpm if the problem relates to alternator output.

What he said .....

x2.

The fuel gauge has a built in voltage regulator that takes the chassis voltage that fluctuates between 12 an 14V and steps it down to a constant 10V to run the gauges so that they don't fluctuate with the chassis voltage. If your gauges move with the lights, then the gauge voltage regulator isn't working. It is a mechanical type, so chances are that the points are stuck. If the voltage is not regulated, the guages will also read high.

It is not a big deal if it doesn't work. You will get used to it.

Okey doke, on the list for this weekend. Adjust idle.

Thanks bikersmurf, for the clarification about amps and volts, electronics are by far and away my weakest point of understanding.

What do you guys think of the upgrading to a GM alternator? I was looking as the Mean Green then I read on here that it is the GM CS 130, IIRC. Might clear up any issues with proper charging and eliminate the external voltage regulator.