Classic/Antique Car Repair: Non functioning instruments on TR7, curcuit board, temp gauge

Question
Hello,

First, let me thank you again for your help last fall when my 1977 TR7 exhibited the hesitation on acceleration.  That issue is finally sorted and the car is running very well.

The newest problem is with the instruments.  The clock and temperature gauge have both stopped working.  Yesterday they both worked fine, today there is no action.  I've checked the fuses and they look OK, but without a wiring diagram I can't go any further.  Hope you can point me in the right direction.


Answer
Hi Doug,

If the horn works, the power is applied to the clock via a purple wire. I have 5 TR-7 clocks and none of them work so it may have died. Try rotating the reset knob by engageing it and spinning the hands several times. The last 2 I had could be revived for a time that way.

On the temp gauge, remove the single spade terminal from the sending unit and turn the key on and see if the gauge deflects the needle, then ground the wire and see if it deflects all the way in the opposit direction. That tests the gauge and power supply. If it does that, the sending unit is bad, if not it is either a brake in that wire or a bad gauge. Or bad connection between the sending unit and the gauge which is mounted on a curcuit board. The tach and fuel gauge have the same power source as the temp gauge on the printed board.

A last possible is to remove the instrument cluster and check the tightness of the nuts on the printed curcuit board where they attach the gauge and check the plug on the cluster.

I hope this helps.
Howard