fresh air light won't work, where does this ground out? Options

[bradtho]

I've got my fresh air blower working again, hopefully I'll actually be able to defrost a bit this coming winter!

anyway, I can't get the little dash light to work. I've got a solid 12v on the hot side, and it makes it through to the ground side with a bulb in, but it never lights up. I've swapped the bulb to another location so I know the bulb is fine.

that pretty much just leaves it not grounding out properly, right? the ground for the bulb runs into the dash harness. I've looked up the wiring schematics but they don't show the indicator lights (or I'm reading it wrong).

any ideas? yeah, I know it's just a stupid indicator and you can barely tell that they're on or not, but it's the principle of it all at this point.

[914Mels]

What year?

[bradtho]

late 72. I've got the updated dash with the vents at the far edges.

[Elliot Cannon]

Check for corrosion in the socket the bulb goes into. Just lately I have had two electrical problems that were easily taken care of by simply cleaning up corrosion. Clean up corrosion, and make sure you have good ground contacts.

[914Mels]

My wiring diagram shows the ground coming off the switch, the only brown wire and going to the ground connection on the body above the fuse box. It looks like from the picture that the switch is part of the ground circuit so don't rule out the actual switch as your problem. I'd jumper a ground to the original gound wire and see if the light works then. If it still doesn't work you know your switch is the problem.

[bradtho]

but if the switch wasn't grounded then the fan wouldn't work, right? the fan's blowing away. I can't find any diagrams that show the wiring for the instrument lights. does yours?

[914Mike]

but if the switch wasn't grounded then the fan wouldn't work, right? the fan's blowing away. I can't find any diagrams that show the wiring for the instrument lights. does yours?

This diagram is correct for most, if not all years:

http://www.pelicanparts.com/914/parts/Elec...lectric_74A.jpg

The switch does provide ground to the motor and the light, but on separate contacts. Under the ashtray was not a great place, a lot of them have been burned and scarred by all the hot ashes, so corrosion in the switch is not uncommon. My switch needed to be cleaned to get the light working, even though the motor did work. Also the light sockets were crusty and the lights still did not work till those were cleaned.

[Valy]

but if the switch wasn't grounded then the fan wouldn't work, right? the fan's blowing away. I can't find any diagrams that show the wiring for the instrument lights. does yours?

The light is grounded through the switch.
The fan and the light use different circuits so the fan can work and the light won't.
Take out the ashtray and look at the switch. The light contact is the one that has the smaller radius. The wire that goes to the light is the single contact on bottom side. You may be able to access it from under the dash.

Found those pictures on ebay.

http://cgi.ebay.com/ebaymotors/PORSCHE-914...e#ht_573wt_1131

[bradtho]

thanks, very helpful. I didn't have time to yank the controls from the dash tonite to try to clean them up, but that inner radius contact is all green and the outer is nice and gold looking. I've got a solid ground where the wire connects, but nothing getting to the plate on top or the wire on the bottom. looks like you found the culprit.

[tradisrad]

I dont like the current flow diagrams; here is a real diagram. #30 is the switch and #63 is the fan blower. Check for dirty contacts, broken wires; if the fan is working then the bulb should be too.

I added a light to the heater side and used the heater lever as the ground.

[bradtho]

I've distracted with other things, but got back to this one today. i cleaned up the contacts on both sides, and the voltmeter said I was good but the light still wouldn't go.

I don't know if I bent the contact cleaning it up or if it was already bent, but it wasn't touching the contact plate. When I'd put the voltmeter on it, apparently I was pushing it down enough to make contact.

Anyway, a little twisting with some needle nose pliers and we're back in business. I now have functioning blue and red lights (just like tradisrad's pic). Just in time for the change in weather.