Temp gauge on zero

[dvisor]

On the bench it's simple enough.

Connect + 12 Volt to the IG terminal.
Connect - (ground) to the E terminal.

Connect about 5 - 10 ohms across the TU terminal and E terminals.

The gauge should swing accross to somewhere near maximum.
Experiment with it, different values will show different deflections.
The gauge is adequately protected and you will do no harm.

I you still get no movement then you will have to strip out the gauges.

Addendum.

As far as the resistor shown above is concerned, measure it with multimeter,
it should be 56 Ohms I think, maybe more, the case is high temp insulation
and a bit missing is not much of a problem, test it for continuity.

Thanks bongoben, this is very helpful. I'm getting 57 across the resistor (shame - I was hoping there'd be no continuity, as it would be easy to solder on a new restor). The exposed part of the resistor is within a hairswidth of the gauge casing, but I don't think it is actually touching.

I'll see if I've got any resistors knocking around to put between TU and E. If not, then I guess a low voltage cell would do the trick instead?

[bongoben]

[

I'll see if I've got any resistors knocking around to put between TU and E. If not, then I guess a low voltage cell would do the trick instead?

No don't do that, it's a Wheatstone bridge circuit and even I would
be confused by the results. It has to be a resistor, if you can't find
one you could short it out but you may bang the needle against the
stop.

While you have it in pieces, pull off the protective can and expose
the coils. Look very closely at the ends of the coils where the wires
join the terminal posts, they are very fine. If you see a broken one
then you need to clean it up, tin it, and re-solder it to the post.

If everything works fine then it has to be the sensor or the cables
which connect the TU terminal to the sensor. Measuring the
resistance of this path is slightly more difficult as you need the
PCB plugs attached. With a cold engine, TU to ground should be
around 2,000 Ohms depending on temperature. I did do a graph
at one time, If I can find it again it could be helpful.

[dvisor]

Nope - I've done the test and the needle refuses to move, so it looks like it must be the coil. There's a coil end going to the E post, which looks intact; and there appears to be two coil ends going to the unlabeled post (the post connected to the TU post via the diode). There's a loose coil end near the IG post So if I connect this up, I should be in business? Is there any reason why I shouldn't solder it directly the the leg of the 56 Ohm resistor? This is probably the most accessible part.

[mister munkey]

PM sent

[dvisor]

PM sent

Thanks Mr M. PM'd you back

[dvisor]

Thanks bongoben for all your help I now have a working temp gauge again! I didn't use a resistor between TU and E to test it in the end, I just shorted it. I cleaned off, tinned and resoldered the copper wire like you said and it seems fine now. I don't know how long it will last though - I'm not the world's greatest solderer! I just need to put it all back together again now.

[bongoben]

Should be OK, I have faith in your competence. Just make sure that when you
replace the 3 Mason wires that the large plate washers mate with the PCB
track and the Mason spade terminals are above and under the spring washer.
Best not to overtighten them, it's a common mistake.