Strange reverse switch stalling problem

[hessiethecrab]

Howdy fellas,

My car has developed an interesting problem. I’ve had a bit of a play with it but I really don’t know what I’m doing. I wonder if any of you guys could help.

My car idles fine until I shift to reverse when it immediately stalls. If I restart it, it will stall constantly, and wont idle without a fair bit of pedal. After driving a short way it will fix itself and run fine again…. until I put it in reverse. The reverse lights don’t come on either.

Removing fuse 9 (which feeds the rev. lights) while the car is idling has the same effect: the car stalls.

With the ignition on, in neutral, there’s 160mA across this fuse. In reverse, there’s no current.

I figure the car must need 160mA across fuse 9 to run properly, and for some reason closing the reverse switch cuts this current instead of drawing extra current for the lights.

I suspect my car is late ‘76 (although it was supposed to be ’77). From the wiring chart, fuse 9 feeds the reverse lights, the horn and some (obviously important) stuff that I don’t understand like cold start thermo switches and the emissions gear (removed).

Occasionally the reverse lights do work and the car doesn’t stall, so it’s not the bulbs.
Shorting out the reverse switch doesn’t make the lights come on so I guess it's not the switch.
Also the fuse is 16A when I think it should be 8A. Maybe the previous owner changed it cos it kept blowing (or maybe not)

Any advice would be great, cheers!

[gldgti]

sounds like something is wired into the current track through that fuse that is something to do with ignition.

using the wiring diagrams, you need to trace all hte output on the fusebox (some will be on the back, some on the front) that connect to either side of that fuse. you mentioned something to do with emissions gear - well if theres a connection to the carb, it might be causing the problem. when you engage reverse, i reckon the lights are drawing too much current for your old and tired fusebox to handle, and it saturates that current track (often happes on track 15 in mk1's... things like turning on a blinker used to cause power failure to the stop solenoid on my old diesel and so the car would stall.)

once you find what it is thats connected to that same track that could be causing the car to stall, you may be able to wire it in separately.

alternately, you could pull the whole fuse box and attempt to repair the damaged track inside (can be done) or perhaps swap the whole fusebolx for another.

good luck.

[hessiethecrab]

Thanks heaps for that.

Any tips on fuse box disassembly/repair? I've starting taking it apart but it seems a bit daunting; lots of loose pins - hope I get all back together. I've only taken the first couple of layers out so far.

All the pins on track 15 seem connected ok.

There's a bit of rust in there. I'll keep digging and see how I go.

[gldgti]

loose pins are a bad sign.

basically once you have the bare fusebox, you pull all of the fuse holders off with some needle nosed pliers (they are just stuck on pins) and then use a couple of little flat screwdrivers to lever the casings off. after that your in, but you're only really able to get at the two outer layers since the ones in between the 2 PCB's arent really acessible without de-soldering the whole board.

you can however test resistance of various paths between the boards and add jumpers if you think it will help.

good luck!

[hessiethecrab]

As you said- I hit a dead end after getting the outside layers off, so I couldn't get to look at track 15.

All it's connections seem correct though, using a multimeter.

It shouldn't be too hard to to wire the reverse lights separatley through a inline fuse. I think I'll give that a crack.

Thanks.