Andre Roodnat

I checked some old threads on this, but couldn’t find a definite answer. Hope you can help.

I installed an amplifier, mounting it on the battery cover. I connected it directly on the battery. I lead the remote-wire and the signal wire through the interior ( next to the passenger door). I took the radio from it’s sled and plugged in the signal out cable. Sofar so good, BUT:
Board computer, odometer, fuel gauge, interior lights, left window winder (only the left), hatch release NOT WORKING.
I checked all fuses and they’re OK. When switching on/off the alarm the signal lights aren’t flashing as they are supposed to. I checked current on the interior lights and there is none. No current on the fuse (44) of the interior lights either. I took out the door switch passenger side and it had current.
Yesterday I started tidying up all cables in the centre console, checking all connections and taping them off. I think it has something to do with the alarm system or something. Some pointers would be highly appreciated.

The lady in question is a ’89 S4 928 euro 5 speed

Andre Roodnat

Oh yeah, and the digital clock is also down, but while I was driving the car (It still drives) I saw it coming back on again, only to fade away some seconds later........


later.

WallyP

The fading clock is a common sign of a short circuit to ground in the interior lamp circuit, often in the lamp over the windshield.

Andre Roodnat

Thanks Wally,

I checked all interior lights, but couldn’t find a short circuit. I measured it and it all seemed OK. When I just drove the car, the red indication lights kept lighting (brakelight check, exclamation sign, hand brake, out of fuel, overheated etc.).

There must be something I’m missing here?

Greg86andahalf

Back to basics.

Try removing the amp's lead to the battery. See if anything comes back to life. Also, how is the charging circuit when the car is running? I wonder if your suffering from a major low voltage condition?

Andre Roodnat

Thanks Greg,

I took off the batterylead a couple of times, to check and also to reset. Waited for about 20 mins. I was beginning to suspect the same as your opting about the low voltage, but the car starts OK. But measuring is knowing, so I'll check it right away. Do you know or anyone know what the relation between all the missing functions can be? I heard the link between the interior lighting and the hatch release. But the strange thing is that the left window winder doesn't work, but the right one does. That should rule out low voltage too.

Greg86andahalf

My thinking was towards low voltage and the ability of a relay to close/open.

BTW, where did you tap ground for the amp? The battery?


[quote] I took the radio from it’s sled and plugged in the signal out cable <hr></blockquote>

Can you elaborate?

Greg

Andre Roodnat

The radio was already grounded. Haven't changed it. The amp is mounted on the spare wheel cover, so I connected it directly to the battery.

Andre Roodnat

I tested all the fuses with the fuse tester on the electrical board. It has a green light which lights up when the fuse is OK. At least that is what I thought. According to the tester they all were OK. After 2 evenings of work with the electrical drawings, I started measuring at fuse 24. Secondary it measured nothing. Primary 12 V. Although I’m happy I found the problem, I’m irritated about the fact this tester is f***.
The only thing which still wasn’t working was the left window. I took out the switch and measured; not OK. I opened it and the plastic was melted by the heat of the contact, melting the contacts shut. So it continuously switched. This triggered the whole problem.

Donald

Andre'
Congratulations on finding the problem. Just FYI, that "fuse tester" relay shorted/bridged/failed on my car, and although it theoretically doesn't do anything, it shut down the fuel brain (I think it stopped a floating ground from completing). After months of frustration my mechanic was looking at the circuit board and the fuse panel, and thought 'why is that relay there?' and pulled it.
Car started. So watch that relay.
Donald

WallyP

The fuse tester is a simple add-on to the EZK (ignition) relay.

If a fuse shows green, the fuse is good. If you have no power thru a good fuse, the problem is usually a bad connection between the fuse and the fuse panel. Ocasionally an owner will use one of the chintzy add-on connectors, where the connector plugs in with the fuse leg. This will almost always cause problems.

One quick-n-dirty fix is to twist the legs of the fuse just a little - this will often increase the contact tightness enough to make the circuit work.