Random electrical issues

[Alex H]

A few random things going on - the speedo just works when it wants to. Most of the time it'll be fine, but sometimes it just bounces between 0 and the speed I'm actually doing. The weird thing is I'm sure I feel the car physically hesitate when the speedo needle drops to 0, then it slightly surges when the speedo needle comes back. Very slight sensation, it's not like it's cutting out.

Also, the other day whilst reversing the reverse lights suddenly went off. Both bulbs ok, all the fuses in engine bay and dash look fine (don't know which fuse the reverse lights are on). The auto reverse rear wiper also doesn't work.

These likely to be connected? Does seem to point to the gearbox, or wiring/earth associated with the gearbox. Does anyone know exactly where the earthing points/straps are located on the 172 cup? Cheers.

 

[Alex H]

A few random things going on - the speedo just works when it wants to. Most of the time it'll be fine, but sometimes it just bounces between 0 and the speed I'm actually doing. The weird thing is I'm sure I feel the car physically hesitate when the speedo needle drops to 0, then it slightly surges when the speedo needle comes back. Very slight sensation, it's not like it's cutting out.

This is really the main problem I need some ideas on. Cheers.

 

[NorthloopCup]

Speedo drive on the gearbox is more than likely up the swanny mate to cause the speedo fault. Easy enough to replace though.

Your reverse light fault could be the switch on the gearbox, a wiring fault or a uch fault. Not 100% certain that the uch has any involvement in the reverse lights though tbh.

If you unplug the reverse light switch and bridge the wires across in the plug (use a piece of wire to complete the circuit) the lights should come on. If they don't it's a wiring issue, if they do it's a switch fault. Make sure you do the tests with the ignition on as well.
Try that to start with. If it's a wiring fault your gonna have to trace the wiring back from the plug at the gearbox and look for any damage along the way.

 

[Poopensharten]

Earth strap should be under the nearside arch liner mate! My Phase 1 was doing the same thing, replaced the earth strap and it sorted it!

 

[Lozza-p]

Mines just started doing it. It's weird cause you can actually feel the car hold back

 

[bmh.01]

If its cup then it'll 110% be the speedo sensor, ecu uses the speed feed so not surprised it gets a little confused.