Hi guys i am having an issue with my heat and fuel gauges, at the moment they both respond but only partially. Both were working very well prior to resolving another issue, let me explain, for a while i was having and issue with my dash lights being very dim and sometimes both of my signal indicator lights would flicker even though they were not in use. I decided last season to remove the dash and do some cleaning. I removed all of the bulbs and lightly sanded the copper contact with 1000 grit sandpaper, i also cleaned all of the posts and interior of the pin connectors, also the two posts for the main feeds. After reinstalling the dash i found dash light constant and bright and no more issues with indicator lights flickering, all of the gauges and switches are working perfectly except for the fuel and heat. The fuel gauge now fluctuates at times and the heat gauge rises an 1/8 of an inch at the most. I am attaching part of the schematics and a picture of the rear posts on the fuel and heat gauge side, this is a spare i have for repair or parts. Any ideas of what to try without having to completely remove the dash again pete

 

Check to see if both gauges are sweeping all the way?
Turn the ignition key on. Ground the sending units and see if thay sweep all the way to full and hot on the gauge. If that is good? you know you have a wiring or a ground issue and not a gauge issue.

 

When i turn on the key the fuel gauge goes to full and then backs off, the heat gauge doesnt move. When you say ground the sending unit do you mean where the heat unit meets the block, .

 

I grounded the heat sensor and the gauge went to full hot, while doing this i noticed the fuel gauge fluctuated. Correct me if i am on the wrong path but i am thinking i should clean to the ground connection to the fuel tank and recheck other grounds. can a poor ground on the fuel tank affect the heat gauge ?

 

Fuel Tank Wire.... Unplug and ground
Water temp Wire at sending unit... Unplug and ground

 

Could have some feed back....
Ok. On the temp gauge.... Replace the sending unit..... But check the ground from the sending unit to the block.. if you dont have a good ground. take the sender out and clean the sender and put it back in and see if it works.. If not then the sender is bad...

On the Fuel tank sending unit.... Yes.. Clean the jumper ground that is attached to the fuel sender and to the steel fuel line. See if that fixes it....
Or if you just have a jumper wire,,,, Jump the ground side of the sending unit to a good ground on the frame and see if all is good. If so then you just need to add a good ground..
Good grounds are a mush all threw the car...

 

I cleaned partially the ground to the fuel sending unit, i will do a better job when i get it on a hoist, hard to reach with just jacks. I see an improvement so im thinking a faulty ground is my issue. I will check all ground locations when under the car. Thanks for the advice and the info on how to test the units. pete

 

Keep us posted...