940 m46 to m90 conversion

[Laird Scooby]

Originally Posted by knuckledragger

Thanks for the kind offer. I saw your advert, but with my box having an inoperative overdrive too, I wouldn't be improving much by swapping it for yours.

As for the fuse, I have had a quick look at wiring diagrams and am I correct in saying its fuse 12, which is also the reverse light fuse? As I understand it, with the ignition on I need to check for 12v to 15 terminal, and if ok there then 12v to the hot side of the switch?

If the tests i outlined show the solenoid is defective, you could cannabalise Lukes box for the bits to fix yours. It's easier to change a solenoid than a complete gearbox!

See my post above, i confirmed which fuse it was.

Originally Posted by knuckledragger

The light doesn't come on at all; never seen it on

You seem to have misunderstood. Make a test lamp from a 12V bulb and holder with leads on it and wire it across the solenoid and take it for a drive. Hit the overdrive switch in 4th above 50mph (i don't know the exact speed but that should be a safe bet) and see if your test lamp lights. If so, you know the electrical side is ok.

[knuckledragger]

Sorry, I meant my dash light has never worked.

[Laird Scooby]

Originally Posted by knuckledragger

Sorry, I meant my dash light has never worked.

It won't until overdrive engages. Then if the bulb happens to be blwon, it still won't light up but you'll feel the overdrive kick in and the revs will drop accordingly.

A silly thought has crossed my mind, you mentioned it had been stood for a few years, it's possible the previous owner didn't even know it had overdrive or how to use it so it might never have been used from new. As such, it might simply be complete lack of use and if you remove the solenoid and plunger, clean it as described further up, replace it and see.

[knuckledragger]

That's a good thought!! Presumably I can remove the solenoid without draining the box (I will change the oil later once I get the overdrive issue fixed, and if I decide to stick the M46)?

I also should mention I removed the positive from the gear lever switch and ran a wire directly from the battery positive to the solenoid yesterday to see if I could hear a click, but there was nothing. I did this with the car switched off, if that matters?

[Laird Scooby]

Originally Posted by knuckledragger

That's a good thought!! Presumably I can remove the solenoid without draining the box (I will change the oil later once I get the overdrive issue fixed, and if I decide to stick the M46)?

I also should mention I removed the positive from the gear lever switch and ran a wire directly from the battery positive to the solenoid yesterday to see if I could hear a click, but there was nothing. I did this with the car switched off, if that matters?

I'm fairly sure you can remove the solenoid (it unscrews from the extension housing) without draining the oil but just in case, have a washing up bowl or similar to catch any oil that spills out. Also have you checked the earth wire on the solenoid? It runs to a bolt on the back of the extension housing.

Linking the output wire from the overdrive switch direct to the battery is an inconclusive test as it still needs to go through the overdrive relay. Depending on the market the car is destined for, it may also have inputs on the relay for oil pressure (from the gearbox) and also speed (from the speedo) so without either of those conditions correct it may not work.

More importantly, with the ignition off, the relay won't do anything anyway.

To minimise any oil spillage, if you reverse the back end of the car onto a set of ramps before trying to remove the solenoid, all the oil in the box will run to the front of it, reducing any oil around the solenoid area.. Check the earth cable where it attaches to the gearbox first though. also see if you have the oil pressure switch on yours and check the wiring to that.

[knuckledragger]

Originally Posted by Laird Scooby

I'm fairly sure you can remove the solenoid (it unscrews from the extension housing) without draining the oil but just in case, have a washing up bowl or similar to catch any oil that spills out. Also have you checked the earth wire on the solenoid? It runs to a bolt on the back of the extension housing.

Linking the output wire from the overdrive switch direct to the battery is an inconclusive test as it still needs to go through the overdrive relay. Depending on the market the car is destined for, it may also have inputs on the relay for oil pressure (from the gearbox) and also speed (from the speedo) so without either of those conditions correct it may not work.

More importantly, with the ignition off, the relay won't do anything anyway.

To minimise any oil spillage, if you reverse the back end of the car onto a set of ramps before trying to remove the solenoid, all the oil in the box will run to the front of it, reducing any oil around the solenoid area.. Check the earth cable where it attaches to the gearbox first though. also see if you have the oil pressure switch on yours and check the wiring to that.

I connected the wire between the battery positive to the solenoid terminal, not the relay. And a cursory check of the solenoid earth shows its fine.

[Laird Scooby]

Originally Posted by knuckledragger

I connected the wire between the battery positive to the solenoid terminal, not the relay. And a cursory check of the solenoid earth shows its fine.

The way you phrased it in the post i quote made me think you'd run a wire fro the battery +ve to the gear lever switch, sorry.

A cursory check isn't enough with an earth, you need to inspect the wiring closely, it could be broken near one of the crimp terminals or corroded on the ring underneath the nut - if in any doubt, clean and/or renew the bits in question.

Did you get a little splash of current when you flicked the +ve wire onto the solenoid terminal?

[knuckledragger]

Originally Posted by Laird Scooby

The way you phrased it in the post i quote made me think you'd run a wire fro the battery +ve to the gear lever switch, sorry.

Did you get a little splash of current when you flicked the +ve wire onto the solenoid terminal?

I don’t think so, the positive feed seemed to do nothing. But I’ll remove it over the weekend and get it on a bench to clean and test it properly

[knuckledragger]

Spent a good few hours today trying to trace where the problem lies. I cleaned the contacts on the solenoid and replaced the spade crimps on the wires going to it. I ran a wire from the battery live directly to the terminal on the back and the solenoid is definely working, so it isn't seized.

Fuse 15 (25A) isn't blown. But changed it anyway in case it was defective.

I removed the relay and connected pins 15 and 87 via a toggle switch. Went for a drive and once at 45-50mph I flicked the switch. Still nothing. No overdrive, no dash light. So presumably this means the relay is OK? Or perhaps it is the relay and I was testing it wrong ? I've never ever heard it click.

Got underneath and had a look at the wires going to the 4th gear switch and to the connector block near the tail shaft. couldn't find any damage

Earth wire from solenoid is fine.

Gave the overdrive button on the stick a continuity check, and seems to be operating correctly.

I presume if this were a mechanical issue with the overdrive itself, I'd expect it to manifest itself with it slipping out of overdrive and/or the dash light to still illuminate. The fact its all dead as a doornail still makes me think its electrical. Could the 4th gear switch be faulty?

At wits end now, not sure whats next to test. I was going to rig up the test light as helpfully suggested by Laird Scooby, but couldn't think of a way to sensibly route the wires into the cabin.

[Laird Scooby]

Originally Posted by knuckledragger

Spent a good few hours today trying to trace where the problem lies. I cleaned the contacts on the solenoid and replaced the spade crimps on the wires going to it. I ran a wire from the battery live directly to the terminal on the back and the solenoid is definely working, so it isn't seized.

Fuse 15 (25A) isn't blown. But changed it anyway in case it was defective.

I removed the relay and connected pins 15 and 87 via a toggle switch. Went for a drive and once at 45-50mph I flicked the switch. Still nothing. No overdrive, no dash light. So presumably this means the relay is OK? Or perhaps it is the relay and I was testing it wrong ? I've never ever heard it click.

Got underneath and had a look at the wires going to the 4th gear switch and to the connector block near the tail shaft. couldn't find any damage

Earth wire from solenoid is fine.

Gave the overdrive button on the stick a continuity check, and seems to be operating correctly.

I presume if this were a mechanical issue with the overdrive itself, I'd expect it to manifest itself with it slipping out of overdrive and/or the dash light to still illuminate. The fact its all dead as a doornail still makes me think its electrical. Could the 4th gear switch be faulty?

At wits end now, not sure whats next to test. I was going to rig up the test light as helpfully suggested by Laird Scooby, but couldn't think of a way to sensibly route the wires into the cabin.

Have you checked the oil level???????????????