I replaced the backup lights switch about 5 years ago. Now switch does work once in a while, and some time moving the shifter stick while in reverse does have lights on and off.

The car has 325k miles.

There seems to be some wear inside the transmission that make it not push the switch button in far enough to close the circuit. I am looking at an other method of turning the backup lights on. It could be a micro switch controling a relay or I could also use the rear fog light switch left of the instrument cluster to turn manually these lights on.

I cannot see an easy way to put a micro switch on the transmission stick right now.

Someone maybe has fixed that problem with an ingenious method ?

Any suggestion is welcome because I want these backup lights working for safety reasons and be legal at the same time.

Hello,

I doubt the transmission selector plate which is part of the shift cover is your problem as history has shown the switches to be problematic.

Volvo has now updated the reverse light switch 2 times and the latest iteration requires the harness to be modified with a new pigtail that has a connector that clips onto the switch.



--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Hi Eric,

Yep, that looks like the switch out of a M47 manual transmission and it looks like the one in the pictures to cut the shoulder back on.

So yes, that’s the one I remembered that screws into that cover plate on top of the gate selectors.
The switch itself never failed me since then.
I have two of these transmissions and the wiring to one of them went bad.
I’m thinking my switches had the plug socket that’s the same used on the windshield washer pumps.
Am I remembering wrong?
So this new switch is a total change out then?
Between either one, I hope it got the reach on the plunger right.

Definitely didn’t know about later revisions but that can transpire at anytime on any car.
They use a disclaimer, in the lower fine prints, to making changes “middle year” on all production lines.
Sometimes it just within a vendors production and cascades.
Volvo doesn’t have any control over so the disclaimers either, so this all runs far and wide throughout our civilization.

I’m trying to remember how big the threaded portion was but if it would fit in a drill chuck a person could try using a rotary tool like a “Dremel” Brand name and scuff it back some with a cutoff tool disc.
Just as long as you try to keep it evenly will help but holding on to the hex is ideal.

I will say I was cautious in how much metal to remove but the bottom inside of the switch casing should have some extra distance of metal for torquing strength not that it needs much.
I stopped at .025 or so.
Don’t remember if it had a gasket to toss too?
I moved it in about thickness of a match book cover or a big man’s thumb nail thickness did the trick. (-:)
The plungers seems to back up plenty towards the contacts it just needed the extra holding power.
As you can see the plunger doesn’t stick out a whole bunch.

Good to hear from you and hope your business is doing well.
I keep you in my mind as my cars are getting older and you are a good source for everything of knowledge and them parts! :-)

Phil

Hi,

I think if you look into any manual for your year car, you will find out the back up lights are turned on by a switch underneath the rubber shifter boot on manual transmissions.
It’s on the left side and when the ring is pulled up to move the stick over to reverse the stick pushes a lever on the switch itself.
It’s all a neat package but you can have a wiring issue from there. I do not know about a relay on these cars being used at all.

I do not know how it was done on automatics but the M46 is a manual transmission and if it has overdrive it will have a button to slide right up on top.
On other M46s from like 1985, I know the knob has a push button and those use a relay to control the overdrive.

Hope this helps.

Phil

"It’s on the left side and when the ring is pulled up to move the stick over to reverse the stick pushes a lever on the switch itself."

You are right, that switch is screwd on top of the transmission and is actuated by a lever of some kind inside. When I replaced the switch with a new one about 5-8 years ago I found it hard to reach and I put new wiring at the same time. I checked yesterday visually and with my hand and found the connections and wires in good shape.

From what I can see the problem originate inside the transmission. This is why I want to bypass that switch.

Just wondering if somebody has done that modification and how it was done.

I could weld some metal on the old switch stem to make it say 1/8 inch longer but I might ruin it at the same time.

Thanks for your input and have a good day.

Hi,

Glad to see you found the switch up in an area that’s on TOP of the transmission.
It resides within the whole bracket bolted onto the transmission. The bracket holds the stick shifter itself.

Within the assembly of the shifter rod there is a rail that guides the stick into first and second gear slot gate.
The ring you pull up moves a pin up and over that rail to let the shifter be gated into a reverse gear slot.

So you are in essence turning a long rod that moves stubs around to move forks to engage the gears front to back.

Going back to the bracket and the rail mentioned it has two bolts for adjustment to properly align the rod to low and second gear gates. If not adjusted correctly it can make getting a smoother shift into those positions harder or less precise.

I will say that either the rail is in the way of allowing the shifter over a enough to push the reverse light switch lever to get pushed over enough.
It’s either the rail or the pin stopping enough movement.

I don’t remember there being an adjustment to relocate the switch as I have not ever had to replace that switch on any of my cars.
I have had to adjust the rail though, on my 1978, over the many years.
I don’t recall if the pin is adjustable out of the shift lever, either, so take a look?
I would think something should move, for a wear and for fitting up allowances at the factory.
I agree, that it’s not a precisely built affair down there.
It might even be considered “Mickey Moused” but its simple and works decently, if adjusted correctly.

I’m suspicious that the rail it set to far to the right or towards the center and it’s keeping the shifter assembly from moving over to the left to hit that lever on the switch enough to close the switch.
There is quite a bit of play for the shifter to bobble around at the hand end but very little movement takes place below.
I think there is a call out of a thickness space between the pin and the rail when it’s engaged in first or second as the rail is aligned to that stroke down the gating between first and second.
You need that gap because it gives more freedom to float over the shifter while it moving front to rear.
That gap goes away when going into reverse.

The rail could possibly still be hitting the shifter handle if something is worn down.
The shifter has a ball end socket and problems can arise there from improper assembling of it.
There are plastic bearings and shims involved. More so, if the transmission has been out of the car?

Guess I’m trying to say the switch should work with some lever to spare and so not needing any welding.
It definitely would be a very thin flexible metal or even plastic in todays cars. I don’t recall what ours is made of?

It’s a friendly thing but it’s been a Long Time Too No See, in this case.
(:+)

Phil
Edit. Just a note about switch locations.
The M 47s have an actual plunger type switch that screws into the top of the transmission.
The plunger rod rides into a dimple that on the shifter rod going to the gates.
Only adjustment is depth by shim or in my case, I had to machine away some the face or shoulder behind the threads.
I got more reach down into the transmission.
Just not quite enough pressure or length for the contacts.
I think it needed about .025 more off the switch body.
Luckily an easy fix except it’s under the car!

Phil wrote: "Only adjustment is depth by shim or in my case, I had to machine away some the face or shoulder behind the threads"

I think I need to do just that. Using a lathe to remove some 0.030-0.040 of the shoulder would push that pin deeper and touch the switch contacts. That switch is realy not old, may be 80 to 100k miles.

Only problem I dont have lathe, but I will look for someone that does little jobs as a hobby. I will operate these backup lights manually until I find somebody with the proper machine tool.

Thanks a lot for your reply.