instrument panel wiring?

[tedlit]

Trying to revive my mostly-dead instrument panel.. right now, the hazard lights work, and the red IGN light comes on at the right time (ie: ignition on, engine not running).

Nothing else works - no clock, no tach, no voltmeter, nothing. Oddly, the panel lights and rheostat work fine. I've also got no heater fans.

I've checked all the fuses, rebuilt the master light and hazard light switches.. but I can't for the life of me figure out what would take out the *entire* dash.. does the dash have a ground strap somewhere?

I've been through the circuit diagrams and workshop manual.. I can't find a pinout of the instrument panel unit to test it though. Can anyone help?

[tr7jim]

Does look like the main earth connection is not connected. The cables are black and bolt to the side of passenger innner front wing by the main fuse box area. The bolt is m6 thread and 10mm spanner size.

Jim

[tedlit]

Thought as much.. how does the earth connect to the panel - is it on one of the two multiwire connectors, or is it one of the two small spade terminals?

[saabfast]

IIRC, its one of the muliplug connectors. Its a bit of a dodgy system as from the multiplug a track goes through the printed circuit to pick up the earth of all the items. It gets damaged particuarly where the illumination lamps twist in due to the heat of the lamps melting the plastic. Having fixed that, I also ran a second earth from one of the small dial holding screws (traced which connected to the earth track). I used the fuel gauge as it was slowly hunting while running and I wanted to improve the earth. I attached a copper earth strap from B&Q (a copper strip about 3" long with lots of bolt holes) to a convienient bolt into the body behind the panel and use this for any earth attachement required for accessories (like the electronic flasher unit).

Alan
Saab 9000 Stg 1
Saab 9000 2.3 FPT Auto
'81 TR7 DHC

[tedlit]

Did a bit of digging on this one today.. looks like I've got no switched live on the instrument panel - the permanent live feed to the clock is fine. If I connect +12v to the back of the volt meter, all of the panel (apart from the rev counter, for some reason) comes to life!

[bmcecosse]

Rev counters often 'stick' if not been used for a while. However it does rely on a connection from the coil, and maybe that is not present ?

[Rich in Vancouver]

The idea of bad grounding may be the answer to my problem. My temp guage is acting wiggy in spite of replacing the sender and the wiring back to the panel connector. I have been toying with the idea of adding a pair of wires going directly to the guage and bypassing the printed circuit.
I would like to be able to rewire the whole panel using conventional wire rather than the printed circuit but am not sure if that could be accomplished.

Rich

1975 TR7 ACL764U

[FI Spyder]

While the plastic circuit can break, it does keep the wiring rats nest to a minimum. When I had my instrument panel out I polished all copper contact points back to shiney copper with metal polish and covered with dielectric grease. I also cleaned every contact point including gauges and checked each bulb on ohm meter. (Some people suggest replacing all bulbs at this point but I find this a bit of over kill.) I have a completely working instrument panel with no problems as a result. The Wicked metal polish product I used has abrasive in it I wash/clean this off with contact cleaner.


TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra