52 Mercury gauges

[Kahuna]

My friend without computer needs some help with a few issues

Mercury (52) has been converted to 12 volts
Engine is a 1980 Lincoln 302

1) Gas gauge: Gauge itself is good, Sender replaced with modern unit from Concourse doesn't work.
I think he needs to have the original sender rebuilt, but not sure

2) Temperature gauge: Gauge is good, Sender used is a single contact for a 52 Merc flathead. Originally 2 were used, as I recall. I think he needs the 2 contact style, as Gauge doesn't work

Can you fellows help?
Thanks so much
Jim

[JSeery]

There is a difference between the original senders and the current ones. The latter are resistance type and the originals worked by pulsing the current. However, a resistance sender still should provide some type of reading on the gauge. The sender is providing a ground to the gauge, so to test the wiring connect the wire at the sender to ground for a short period of time and see if the gauge shows a reading. Another issue could be the sender being the wrong resistance for the gauge.

The original temp sending units were a single contact and a dual contact. The dual contact is just an on/off switch and would not be used in a non-flathead application. Again, the single contact sender is providing a variable ground to the gauge. If there is a non-conducting sealant on the sender threads it will not ground properly.

[Kahuna]

Thanks so much, J
Really appreciate the help
Jim

[flatheadmurre]

My way of testing the wires to the gauge and gauge is a simple 50ohm resistor on clip leads...one cliplead to ground and other to the wire going from sender to gauge.
That should put the needle on the gauge in the middle somewhere...indicating wiring and gauge works.
Also some of the regulators sold for converting 12v to 6v for the gauges are so poor they cant put out enough current and things like fuelgauge just ends up showing half when tank is full.

[tubman]

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Here's a tip that may be useful. You can buy very thin non-adhesive copper tape about the width of regular teflon thread sealing tape. I got some from my neighbor who is an EE about 5 years ago. I have used it instead of teflon tape since then with no problems at all . The copper is soft enough to deform and seal the threads but it doesn't interfere with the sending unit ground. I think I saw it offered on Amazon a while back.