1979 spyder instrument panel lights

Gotta love that wiring . . .
maxdog
Posts: 78
Joined: Thu Jul 07, 2016 11:27 pm
Your car is a: 1979 spyder 124
Location: Montreal Quebec Canada

1979 spyder instrument panel lights

Postby maxdog » Thu Nov 30, 2017 4:20 pm

I decided to replace my panel light bulbs . I'm halfway there . The center panel lights and the associated electrics all work , but I have NO instrument lights .
I have the panel connected to all the wiring, but not installed in the car. Is this the problem ? is the complete panel grounded by the four bolts which hold it in place ? I cleaned and tested the instrument rheostat ,does the power flow from the rheostat to the panel lights and then to ground , or from the lights to the rheostat and finally to ground ?is there a problem here or is it elsewhere ?
Any help would be grate fully received
Thanks
Maxdog

dinghyguy
Posts: 78
Joined: Thu Jul 20, 2017 7:41 pm
Your car is a: 1979 spider
Location: Vancouver, Canada

Re: 1979 spyder instrument panel lights

Postby dinghyguy » Thu Nov 30, 2017 8:22 pm

Hi Max dog,
No need for panel to be installed.

Power for indicator lamps (no dimming):
fuse to connector C33 - yellow black wire
C33 to C28 - yellow black wire
C28 to gauges - yellow red wire.

Power for dimming lights:
fuse to connector C33 - yellow black wire
C33 to rheostat
Rheostat to C33 and also hazard switch - white red
C33 to optical fiber light and then C28 - white red
C28 to bulbs in gauges - white red

all then go to ground after bulbs through the white black wires.

Suggest you download the information from Mirafiori.com but you have to be member. You can get all the wiring diags.

Hope that helps.
dinghyguy
1979 blue spider
2008 blue audi A3
1971 16' mirror camping dinghy (team coastal express in 2016 race to alaska)
2004 11' mirror dinghy

spider2081
Posts: 2118
Joined: Fri Jan 27, 2006 11:45 pm
Your car is a: 1981 Spider 2000
Location: Wallingford,CT
Contact:

Re: 1979 spyder instrument panel lights

Postby spider2081 » Fri Dec 01, 2017 7:52 am

Have you checked for voltage at the rheostat? If I remember correctly power for the rheostat can come from the "hot all the time" circuit when the headlight switch is in the center position and from the "hot in start and run" circuit when the headlight switch is in the "Headlights on" position which is the down position. The head light switch from the factory has 3 positions "up" is off , "center" parking and dash lights with ignition switch off and, "down" headlights, parking and dash lights with ignition switch in the on position. You should have voltage at the rheostat under both conditions.
The rheostat has an internal fuse. Have you tested for voltage at the output of the rheostat.
The instrument cluster dash light ground is made at the grounding pod above the ignition switch behind the dash.

maxdog
Posts: 78
Joined: Thu Jul 07, 2016 11:27 pm
Your car is a: 1979 spyder 124
Location: Montreal Quebec Canada

Re: 1979 spyder instrument panel lights

Postby maxdog » Sat Dec 02, 2017 11:49 am

Thanks guys
Looks as if I'm going to be spending the weekend upside down under the dashboard .I now have some idea of what to do next and a wiring diagram to help me
Cheers
Maxdog


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