Author Topic: Some helpful gauge testing tips  (Read 1127 times)

Offline HP_Cuda

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Some helpful gauge testing tips
« on: August 01, 2016 - 06:38:13 PM »

Well I have gone down the road of figuring out why my fuel gauge decided not to work.  :villagers:

Some tips I got were:
- Ground the post and provide 5V power to the other side - this should peg the gauge. (hint: don't do this for long)
     Tried this in the car with no success, so I pulled the cluster and yanked both the fuel gauge and temp gauge. Turns out the fuel gauge had a wire that was fried off one of the posts. I had a spare fuel gauge so I used it. Decided to test them out of the car. I have a power supply which I can choose either 12V power or 5V power. I took power from the 5V rail and ran that to the power post on the gauge and then ran the negative to the other post. Both gauges worked a charm and jumped up and started pegging. Don't do this for long.

- I had a spare voltage regulator so I pulled the original one and swapped it as it passed the test below.
I didn't know whether my gauge cluster voltage regulator was bad. Found this vid which was great and it shows you how to test it:
https://www.youtube.com/watch?v=0qVfKiujK5A

- Put everything back in the car and tested the fuel gauge while the cluster was grounded to the dash frame. Whoa it worked and I have less gas than I thought!!! A little less than 1/4 tank and I think when I started I had over 1/2 tank.

So it looks like not only the VR had gone bad but the fuel gauge itself was a goner. But now everything is working like a charm!

If I had to do it all over again, if the ground test doesn't work while it's in the car you will have to pull the gauges. Make sure to test them before you buy them if you can - although a visual will work if you are looking for loose wires or burnt wires which would tell you that the gauge went through a short condition and started melting down. Definitely test the gauge before you put it back in the car.

An easy way to find out if your gauge has not burned out and has a wire that is no longer attached to one of the posts. Take your multi-meter and run an ohm reading across both terminals. This will do 2 things for one it's a continuity test and the second it will tell you the resistance. I can tell you both the fuel and temp standard gauges show 12ohms whereas the one that burn out shows nada.

Hope this helps someone in the future.  :2thumbs:
1970 Cuda Clone 440 4 speed - sublime green
1970 Cuda 383 4 speed - yellow - SOLD




Offline YellowThumper

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Re: Some helpful gauge testing tips
« Reply #1 on: August 03, 2016 - 10:50:01 AM »
Good info. Thanks for taking the time to post.
Will definately add it to my archives for the future.
Also glad you got it sorted.

Mike
Removing the warning labels one at a time.
Nature will take care of the rest.

Offline HP_Cuda

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Re: Some helpful gauge testing tips
« Reply #2 on: August 03, 2016 - 12:12:21 PM »

Thanks I'm glad someone could gain from my tribulations.

One other thing to add:
Since I have built my own power supply that can output 12V and 5V and I know not everyone has that - you could also take 3 x AA batteries to test out a gauge while it's out of the car using the same method I mentioned above.

 :thumbsup:
1970 Cuda Clone 440 4 speed - sublime green
1970 Cuda 383 4 speed - yellow - SOLD