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SM5 weird behaviour? - Howard Wright - 24-08-2024
Hi All
The last few trips in the van have been punctuated with the odd misfire and occasional starting problems. It culminated yesterday with an almost constant problem, with the car cutting out every few hundred yards. I discovered that the ignition switch on the SM5 switchbox could be fiddled with to help with the problem. An easy fix, or so I thought. I’ve had the box to pieces cleaned the contacts checked for continuity etc etc. But putting the box back in the car I find that …
Switching from off to summer charge moves the ammeter needle to about 2 amp discharge. That’s good!
Switching it further to full charge the ammeter needle stays at 2 amps. That’s good.
Switching it back to half charge causes the ammeter to register zero. That’s bad.
Switching it on to full charge the needle remains on zero. That is also bad.
Switching it off then back on and the ammeter registers 2 amp discharge.
The switching back from full charge to half charge almost always results in zero amps, but occasionally the needle stays on 2 amps.
I’ve a feeling that this is the cause of the misfire and cutting out but what could cause such strange behaviour. Could it be the diode cut out or is it still bad contacts in the switch box? I have a separate earth to the bolt on the starter motor housing and one to the floor pan and chassis.
Thanks in advance for any help, comments
Howard
RE: SM5 weird behaviour? - Howard Wright - 24-08-2024
Well that took some detective work!
It was the diode, or more precisely the connection to the diode.
I hide the small biscuit size diode in the fuse box on the C1 cutout. It is joined to the cable with a chocolate box connector. It is a tight fit and one of the wires had come loose and was shorting to the cover.
Cheers
Howard