Amazon: M41 Reverse Light Switch

[gothamus]

I have searched the manuals, forums, inter-webs for a few days. Looking for how to fit reverse light switch to the m41 on my Amazon. I have the old one off and new one in hand. It doesn't twist in and it doesn't seem like the rubber pushes over some lip inside. Indeed, I can just set it on top of the hole with no resistance which makes me think it is just superglued on to the case.

Accessing from gear lever hole after removing the lever. Read a post about heating switch in boiling water, pressing on with 4mm socket extension (bit small). Otherwise, plug hole and install manual reverse switch to dash. The inner stem on old switch was missing. Wonder where it went

[142 Guy]

Are you talking about this miserable little thing?

https://www.cvi-automotive.se/en/art...switch-on-gbox

If so, I have replaced it on my 140. I can't speak to the Amazon; but, on a 140 I don't think getting access to the pressed metal housing on the back of the gearbox through the gear lever hole is ever going to happen. When I replaced my switch I had to raise the front of the car on blocks to allow me to get under the transmission. Laying on my back I reached my hands up to the top of the transmission and used a mini ratchet with a Philips head (#2 as I recall) to remove the two screws holding the brake light switch housing in place. My mini ratchet was about 50 mm long, something like this

https://www.amazon.ca/Neiko-03044A-M...ag=googcana-20

Removal and replacement of the reverse light switch housing is all done blind and there is not a lot of room to work - hence the need for the mini ratchet. Even with the housing off it was a bit of a push to get the switch in so that the rubber retaining lip on the switch was completely engaged with the hole. A little silicone lube facilitated the installation. I don't think I would have had the strength in my hand to get the switch fully into the hole with the housing still in place on the transmission.

[Ron Kwas]

Gotham;

Warming the polymer support of that (spring) contact is definitely recommended before trying to insert it into the mount...and I hope the replacement you got is new production, and not NOS where a lot of the plasticizer has left the material during its time in storage...in that case, installation is going to be quite difficult, so I recommend removing the alu cup from the Gearbox, supporting the area around the hole very well before attempting to push it in...lest you dimple the can with the force required to install...it would be a bear to do with gearbox installed in the car...

If I needed to replace/install a working Reverse Light Control Switch, I probably would have drilled the cover and installed the other style switch...

"inner stem on old switch was missing. Wonder where it went "...if that contact was not controlling the minuscule coil current of a Relay (none is shown in the 1800 Wiring Diagram, and I expect an 1800 is where your M41/OD likely came from), then it was subjected to the full Lighting current (which is not a real lot, but if there was ever an overload, it would have been subjected to that also, and that could have deteriorated it heavily, until it finally fused open, and "disappeared"). Your 122 should have a Relay for the Reverse Lights (this was standard in a 122 Wiring Diagram), but I recommend also adding a snubber diode (1n4004) to quench the arc and plasma occurring at the switch contact. This will give the new switch its best operating condition for a long service life.

Ref for Snubber Diode: https://www.sw-em.com/Ignition_Slave...erminal_relays

Cheers

[gothamus]

Thanks for the info 142 Guy, Ron!
I made one embarrassing error- I have a m40 - no overdrive. Sorry for my error.

My picture shows the view through the gear lever hole. Angle, reach etc mean I will jack car again and reach around from below. It may only be to put a grommet over the hole.

Switch is new from CVI- Volvo certified baggie. Matches the one removed and what 142 Guy posted. The wire from the switch runs up to the relay in the engine compartment. Wiring matches diagrams for amazon. Relay is tested.

If I were to press the switch into that hole I would succeed in pushing the entire switch into the gearbox. I was thinking the stub the spring is on would squeeze through an inner hole and be supported. I don't see that here. I am pretty sure nothing else came off with the old switch. I had a sheet under the car and when I took it up I did it in a way that anything on it would be found.

The aluminum housing has 3 screw into the gearbox. Not hard to remove, but I am unclear what else the housing is covering and possibly supporting. If it is only a cover and not integral to anything in the gearbox, removal won't be so bad. But I need to be absolutely sure about that first.

Those diagrams all cut off the side of box where the switch is located. I don't see further parts listed in the catalogue diagrams. I do have a hole in my dash for a little switch anyway...

[Ron Kwas]

Gotham;

That alu can simply covers the three Gear Selector Rods, no big deal...and it positions the spring contact to be grounded by the Reverse Gear Selector Rod when the gear is engaged. If you have access and can simply remove the can by unscrewing the two securing screws, I would recommend it...then the work can take place somewhere infinitely more comfortable than on your back under the car (if it was possible there at all!)

Cheers

[142 Guy]

As Ron notes, there are no 'parts' inside the cover so nothing to fall out on removal. Your cover is slightly different than on the M41 on my 1971 B20E in that the hole for the switch is on the top of the cover rather than on the side; but, the cover is in the same location on the M41.

The 140 parts manual indicates that there were at least 4 versions of that cover used between 1966 and 1972. All of them are retained by two long screws going through the back of the cover. This picture (lower left) from Skandix shows the top mount variant that you have which is retained by two screws and that 380360 is the correct (as in only) part for use with that cover.

https://www.skandix.de/en/spare-part...light/1012676/

Looking at your photo the hole looks pretty much as expected except I don't recall that little keyway that shows up in your photo. In the photo there is a polished ring around the outside of the hole and I expect that corresponds to the outer rubber lip on the contact. I expect that if you pull the cover off you will find that the 380360 contact assembly will fit securely in the hole.

Looking at the Skandix photo, removal of the cover should be fairly easy with a stubby screwdriver not requiring the use of my mini ratchet because you don't have the overdrive blocking access to those screws.

[gothamus]

Thanks for the info on the cover. Excellent info. I tried to find that skandix page. The path I followed didn't result in the black and white image.

I will update later, including some pictures, whether it is sorted out or not. Much appreciated.