THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

Well no markings is a bugger. I don't know Rob not being an Auto man. In my scratching I see there is a thing called an auto adjusting inhibitor switch. Now that looks like trouble looking for a place to happen.

Thanks Glyn. The new switch does not have the terminals numbered so it is impossible to tell which is starter or reverse circuit. You can put a continuity tester across the terminals so you know when the connection is made when the plunger is pushed but not knowing which is which makes it very difficult to set up. Is the reverse light on when the plunger is fully depressed or is this the starter circuit?
I am due to fiddle more over the weekend.

A Volvo guru wrote a white paper on this issue but i can't find it on the internet. I've searched for hours. Should have saved it.

Simplified.

[attachment=0]BW35 inhibitor switch adjustment.pdf[/attachment]

Thanks Glyn.
The BW35 manual I already have but it is useless as it just says 10. Adjust the switch. 11. Check the switch for correct operation.

The Volvo manual is a lot better and describes the procedure and testing in more depth. I will print out the relevant page and save the rest in my manuals folder for future reference. I have already tried this method once and as stated I got the inhibitor part to work but could not then get the reversing light to work whilst it was in this set up. I must obviously try harder which I will do next week now as I have another wedding on Friday.

Manual BW35 ~ covers adjusting inhibitor switch.



[attachment=1]Volvo Automatic Transmission BW-35.pdf[/attachment]

[attachment=0]BW_35_manual.pdf[/attachment]

If it's any help the 35 was fitted to lots of other cars including Rover's and Ford's, have a search online for any workshop manuals that might show the switch and wiring - just thought.

I just thought I would add that there is no information regarding the setting up of the inhibitor switch on the BW35 gearbox in the S Type manual which only covers the DG250 box where the inhibitor is on the dash.
The 420 has the model 8 which is different again and although th ebw35 was used on the later 340 and 240 Mk2 all my Mk2 manuals only cover the DG250 again.
Does anyone have access to a Daimler 250V8 manual as they used the BW35 box and might shed some light.

Recently I have had an intermittent problem with starting my car a 1968 3.4S with the BW35 gearbox.

When cold whilst in PARK or NEUTRAL once the key was turned the button would ignite the engine no problem. As the engine got hotter and up to running temp then with the key turned there were several times the car would not start on the button and I would have to revert to the button on the solenoid under the bonnet to start the car.

I decided the problem was either with the solenoid or the Inhibitor switch on the side of the gearbox with the BW35. Bought both and changed the solenoid first as it is the easiest to get to but the problem continued.

To get to the inhibitor switch there is an inspection panel on the left side of the gearbox tunnel under the carpet held in place by six cross headed screws. Access is good and once the four wires are removed, making a note of where they all went, the Inhibitor switch is unscrewed from the side of the gearbox.

[attachment=2]IMG_9936.JPG[/attachment]

The electrical terminals are marked 1,2,3,4 meaning 1 and 3 are connected and 2 and 4 are connected. 1 and 2 for the ignition, 2 and 4 for the reverse light.
First thing I noticed was two opposite terminals 1 and 3 were very loose against their rivets and it only took a small twist and one of the spade connectors came away in my hand. So the problem lies in these bad connectors. I worked out that there are two terminals for the reverse lights which are opposites and two terminals for the power to the starter button which were the ones that were broken.

I had a new inhibitor switch ready to fit but when I compared the old and new they were different thread lengths and the new one had no markings to signify which terminals were for reverse or ignition button. As the old switch was broken I took it to pieces to see how it works internally. So basically there is a plunger and something inside the gear box pushes this plunger in to different depths depending on where the gear lever is. The plunger then makes an electrical connection across the terminals depending on the depth it is pushed.

[attachment=0]IMG_9940.JPG[/attachment][attachment=1]IMG_9939.JPG[/attachment]
The old switch is on top the new below. It is clear that they are different plunger lengths.

Problem is as there are no markings on the new switch to work out which terminals are 1 and 3 or 2 and 4. I can work out by putting a multi meter across the terminals and pushing the plunger which terminals work at different plunger depths but that does not help as I do not know the depth the plunger should sit at when screwed in the gearbox.

I have screwed the inhibitor switch in and have been able to set the distance so when the car is in P and N the starter button works and the car will not start in gear. Problem is at this setting the reversing lights are not working when you then put the car in R. I have tried swapping the terminals over and screwing the inhibitor switch in further so again I can start the car in P and N but still the reversing lights will not work. I know there is power there because when you jump across the terminals the reversing lights come on.

The problem lies in trying to get the inhibitor switch screwed in to the correct depth to allow the plunger to be depressed by whatever is in the gearbox to the right point that allows both the starter button and the reverse lights to work.

I gave up last week as I had a wedding the following day and as long as the car started I did not mind that the reverse lights were not working but I am going to have another go this week to set it up but would appreciate any insight or assistance.