BW35 Isolator Switch Setting

keynsham1

keynsham1

Active Member
I know there have been threads here before but I am having a nightmare setting up the gearbox isolator switch. All was fine until I had the gearbox rebuilt. I assume during this, the switch was removed and replaced in the usual set position. My first problem was that the car was fine when cold but when hot the isolator stayed isolated in P and N and the car would not turn over. After 10 minutes or so however, all was back to normal. I assume it had cooled down a little and gaps may have changed with the switch. So assuming that was the case, (and after replacing the switch to no avail) I reset the position of the switch in accordance with the manual. The outcome of that was that it will now start in N but not in P!

It seems that the switch makes a connection for the reversing lights when the plunger is not pressed in and as you press it in the reversing light connection is broken and after one turn the isolator connection is made. So, I am thinking that if I screw the switch in a little further then this might help? I am a little curious as to why it will start in N but not in P though.

If anyone can shed any light on the it would be greatly appreciated!!
 
Yes, 45 degree are reversing lights, straight ones are isolator. I just looked in the manual and the plunger is operated by a detent plate so the detent for the P and N locations is different. This could explain why N works and P doesn't.
 
Before you get in too deep disconnect the rod from the selector lever and operate the lever manually and see if it works that way.
 
Do you mean that the selector rod may not be moving the detention plate in the right place and need to be adjusted?
 
There is so much scope for play in the linkage and lever, which can prevent full travel of the selector lever, so disconnecting the linkage eliminates that as a problem. Just be careful when testing.
 
Thanks Harvey, I have just checked the position of the operating rod. Basically I wired a multimeter to the two connections for the isolator on the switch. It should have shown open circuit for 1, 2, D, and R, and closed circuit for N and P. But the P position stayed open circuit. (All with the engine not running of course!!). As I pushed the selector arm upwards with my finger, the P position went from open to closed circult. So I have adjusted the length of the operating arm by screwing it in four turns which now gives me a closed circuit for P and N and open for 1, 2, D, and R. I checked the R connections with the meter too and all now seems well! I did notice that there is a fair bit of wear on the sliding block where the vertical and horizontal rods join too which doesn't help! Just a 54 year old car I guess!! Thanks everyone for the help. I am not sure I would have arrived at the rod length as being the issue!!
 
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