marty964

Hi, and thank you in advance for your responses.

I have a 1990 C2 it has about 100K miles. Has been stored in a heated garage for 25+ years and driven about 20 times each year totaling about 800 per year. Haven’t had any electrical issues previously. On the same day I lost my Tachometer (it won’t move at all stuck at zero) power windows, power mirrors, all interior blower fans, windshield wipers. Car starts and idles fine. Drove it about a mile or two — haven’t driven it further as I don’t want to risk it as I don’t know what other electronics are out. Everything operates normally outside of what’s mentioned.

Headlights, power seats, radio all work fine. I checked all fuses in the luggage compartment - all are fine. I have not ordered a new DME relay, or window relay as I’m suspect they are related. I think I’ll be chasing a bad ground issue - however I think a wiring diagram could help isolate my issue. I do not have a wiring diagram.

Any and all help would be appreciated.

Thanks!

Rocket Rob

Marty - You can download the factory workshop manual in PDF here. Good luck with the repair. Have you had any work done on the car recently?

https://early911nzdownloads.yolasite...op-manuals.php

r-mm

Every ground on the car is well identified in those documents and not all that hard to access for cleaning. Get a brass bristle brush, a bottle of de-oxit and clean each and every one of those ground up, re-tighten the bolts. Do the same for the battery terminals and primary body ground at the starter motor. Replace the negative cable (cheap insurance). Check voltage while running. Report back!

Above pays so many dividends for all future trouble shooting.

Spyder_2011

In addition to above, check for mouse droppings in/around the car and any evidence of nests. If the cars been sitting a while a mouse may have nested in it and chewed up some wires. Hopefully not the case but worth ruling it out.

lfl215l

Check your ignition switch

ZG862

Once you have a copy of the wiring diagrams (and the excellent "How to dead" document that I'll add a link to when I find it), it may be a good idea to check for things in common to the failing components. Whilst a common earth is likely (& hence advice above), it is also possible that they share a common power supply bus or connector. My experience in recent weeks is that even common crimps on spade recepticles can corrode enough over the years to mean insufficient current is flowing for a component to work properly. I bought a jar of conductive paste to use in reassembly.
Fortunately, whilst tedious, the problems need not be terminal (no pun intended) so it really is worth investing the time getting familiar with those wiring diagrams!
Hope this helps - for all I know, you're a qualified electrical engineer and I'm teaching you to suck eggs; Apologies if this is the case.

Z

marty964

Rocket Rob thank you for the link to the manuals - and thank you everyone else for the responses

Wiring diagrams are not that easy to understand but at least I have found a few of the grounds. I’ve given it a few tries (lots of work, and young children make it near impossible to find the time) but I have cleaned the body grounds in the luggage compartment and the front body mounts in the fenders. Also under the seat. They all looked clean and without corrosion.

I think unrelated to the grounds cleaning, I gave the ignition switch a good jiggle) my power windows and mirrors became operational however the tachometer was still dead. This was a fleeting moment, as when I went back a few weeks later they were no longer working. Makes me think I should give the ignition switch more attention. Also I can’t confirm this was a result of the ignition switch jiggle because I also moved every fuse in the box (they are all fine)

I haven’t driven the car. There are no mice anywhere in my garage - car sits on a 4 post lift.

Appreciate the feedback and any further advice.

Porsche123]

I agree. If your main beam flash will also not work the chances are that it is the ignition switch not returning to its original set position (old lubricant eventually go solid.

The simple test is to start the car, try any of the listed "electrical faults" (I'd go for the lights - its easier to see) and gently turn the key to the off position. You will be surprised how far it can turn before the car engine turns off.

If everything then works, it is the ignition switch. My one was a from the mechanical cylinder barrel rather than the connector block. That said, swapping out the electrical element is A LOT EASIER than the alternatives. Good luck.