200Tdi Ninety

Hi

This is a new post - hoping that someone can advise me how to systematically troubleshoot a problem I am having with my 1986 200Tdi Ninety.

Following an attempt to sort out a couple of issues........

[
- trying to wire up the fog light properly. Then put back to how it was
- trying to get the instrument lights working properly. Put back to how it was, except I am using the instrument lights switch and connection
]

........behind the instrument panel (also replacing the cowl with a metal one along with the instrument panel itself) I have a situation where ground cables are being energised behind the relays

Here are some tests I have done with the relays removed. All these problems only arise when the engine is running. So it's almost as if something (that is only on when the engine is running) is causing voltage on ground.

Testing at relay sockets:

• First relay socket (Starter relay) sometimes gets volts ground side only. This leads to the starter being reenergised AFTER starting (this was my original post). I've a workaround to this using a switch to jump across the output wires. However, I don't want this workaround to be permanent.
• Second relay socket not energised on either control side (+/-). Not sure what this relay is.
• 3rd relay socket: 14v on both sides. I THINK this is the glow plug relay, but it always seems to have volts. However, I test the glow plugs at the connection on the cylinder head and there never seems to be any Voltage.
• 4th relay socket: 14v on live side only (control) - Not sure what this relay is but, when the relay is installed, it's getting warm and is energised all the time
• 5th relay not energised either side (this is the dip/hi beam relay)

One of these relays is probably the fog light, but PO has rerouted that to run directly from the switch, as far as I can work out.

So there must be a fault/short/loose ground wire or something somewhere which is causing these anomalies (ie. starter reenergising, temperature gauge and (I think) fuel gauge not working properly). ?

My question is, how do I troubleshoot this? There are quite a few earth points in the car? And obviously the main wiring loom behind the dash is not accessible.

Thanks!

There aren't that many earth points and the loom behind the dash is accessible. The dash is easy to remove and if it means getting better access to solve your problem then it's worth it. It sounds like a short to me though but it may not be behind the dash, they're very prone to chaffing inside the chassis and certainly when I removed my loom for the chassis swap there were a lot of points where the wiring was very worn.

the_wolf said:

There aren't that many earth points and the loom behind the dash is accessible. The dash is easy to remove and if it means getting better access to solve your problem then it's worth it. It sounds like a short to me though but it may not be behind the dash, they're very prone to chaffing inside the chassis and certainly when I removed my loom for the chassis swap there were a lot of points where the wiring was very worn.

Click to expand...

Thanks. I have noticed some chaffing of a white and green cable going to the fuel sensor. There is continuity between the white cable and the ground that runs alongside it. The white cable is energised when the engine is running - but not the ground interestingly.

I'd like to solve but I kind of feel a bit out of my depth! Little knowledge, dangerous thing etc. It would be great if there was a way of identifying exactly what location was causing it.

I actually had been planning to replace the chassis harness as there has been a lot of hacking about at the rear.

I'll look further behind the fuse panel as well.