Temperature gauge woes - 1963 Coupe

[Bruce R.]

The temperature gauge in my 1963 fuel injected coupe has started to act erratically. Sometimes the gauge works perfectly, other times the needle goes to the far right of the gauge, other times the needle goes completely underneath the gauge. Any ideas please?

[Bill Jackson]

Re: Temperature gauge woes - 1963 Coupe

Sounds like a bad wire to the sending unit. Warm the engine, shut it off, turn the key back on then have someone watch the guage while you wiggle the wire inch by inch. Pay particular attention to the sending unit clip and anywhere it passes through clips etc.Good luck.

[Jack H.]

If that doesn't get it....

remember the internal construction of the gauge is such that it's biased to read cold. With the temp sender fully disconnected, turning the ignition on will generate a constant/solid 'cold' reading. This is because there are really three connections to the temp gauge....

Power (via the ignition switch), variable resistance of the temp sender at the engine block, and GROUND REFERENCE by way of being physically screwed into the dash gauge cluster. Hence, there are TWO ways to make the temp gauge give erratic readings:

(1) The connection to the sender is intermittently doing a short circuit to ground (HOT reading) and then an open circuit (COLD reading).

(2) The reference ground at the gauge installed in the dash cluster is 'bouncing' with respect to true chassis/battery ground....

Number two is typically caused by screws fastening the temp gauge into the instrument cluster being loose, the cluster itself isn't grounded properly, or one or:

(a) one more of the radio interference capacitors are failing causing B+ to be injected into the dash cluster itself.

(b) one or more of the behind dash power lines has chaffed insulation and is intermittently touching the metal of the dash cluster pushing it off ground.

[Ray C.]

Re: Temperature gauge woes - 1963 Coupe

Hi!

Just had the same type of problem on my 65. The dark green wire connects to the interior of the car through a connector block at the firewall next to the steering column. There is a second connection point near the steering column that clips to a support brace under the dash. I disconnected both connections points and cleaned with contact cleaner. My problem was in the second wire connection.

Hope this helps!
Ray #36314