Occasional stalling when flashing main beam

[TheLeeds]

This is an odd one, although I'm sure I've seen it mentioned before somewhere. My 940 2.3 lpt sometimes stalls if I flash the main beam headlights. It doesn't do it all the time, and especially not when I try to make it do it to check why.

I've checked the obvious battery connections and under bonnet earth points, and all seems ok.

Any ideas on a possible reason and / or cure ?

[Laird Scooby]

If memory serves correctly, there's a multiple earth point behind the left hand headlamp that is shared by the headlamps and the ignition module which is hidden by the air cleaner.

Could be worth checking this by removing the screw/bolt that secures it, cleaning all connections with emery cloth or similar, refitting it and then covering in silicon grease or vaseline or similar to protect it. Also check the security of any crimped connections on the wiring, an ok looking crimp might be failing/failed internally so the "tug test" comes into play - hold the terminal and tug the wire to see if there's excess movement (it could be the wire is broken inside the insulation) or if the wire comes clean out of the crimp.

Hopefully that should see you right, it sounds like a borderline eareth fault that you won't find by visual inspection alone.

[TheLeeds]

Originally Posted by Laird Scooby

.........Hopefully that should see you right, it sounds like a borderline earth fault that you won't find by visual inspection alone.

Thanks for that. I noticed a few times when it's happened, the stereo presets disappear as well, as if there's a brief but total failure of power somewhere.

[Laird Scooby]

In that case you also need to check all the connections to/from the battery including all earths as well as feeds. Don't forget the longer leads that run from the battery to the starter, battery to chassis earths and any others you can find.

[TheLeeds]

Originally Posted by Laird Scooby

In that case you also need to check all the connections to/from the battery including all earths as well as feeds. Don't forget the longer leads that run from the battery to the starter, battery to chassis earths and any others you can find.

I had a look at that and they're all fine. (I removed and cleaned them anway, just in case). I cleaned the battery terminals as well while I was there, but the problem is still there, but not all the time. Are there any earths or other major power connections inside the car that could be loose, for example, behind the dash / instrument binnacle ? I think I remember seeing some earths once when I replaced a duff speedo on an older 940, but it was a few years ago so I couldn't be sure.

Another thought I had is this. Over the winter, the battery went flat a few times, especially when I didn't use the car for more than a few days. The odd thing was, when I jump started it, the radio presets had all been lost, just like what still happens if I flash the main beams and the car stalls.
I thought I'd better ask on here first, in case anyone else has ever had this problem, and to save me having to start pulling the car to bits unnecessarily.

[Laird Scooby]

Just to clarify, are you saying when the engine stalls because you've flashed the headlights the memory for the radio is lost?

Also a diagnostic question or two :

If the headlamps are on (i.e. dipped beam) and you operate the headlight flasher, does it still stall?

Have you replaced any fuses in the fusebox at any point? I'm referring to the fusebox behind the ashtray that can be slid out for access.

Last diagnostic question, bit strange but bear with me, is the action of the flasher switch nice and positive or a bit "woolly round the edges"?