M-46 overdrive relay does not respond when car is cold in the morning. I mean 0 to 15° F. It will work when car is warmed up and I can then see the green pilot in the instrument cluster. It does test OK with a 12v source on the bench in my warm garage.

I noticed there is quite a bit of electronics in that relay. Could there be some components getting weak with time ? And can it be fixed ?

I have an 86 doing the same thing. My mechanic tells me the o rings in the overdrive need to be replaced. IPD sells an overdrive overhaul kit. I'm going to do mine this summer. Warm weather is on the way.

Wait, I did not mention the overdrive not engaging but the relay not acting. I can tell this because the green OD pilot light in the instrument panel is not coming on when relay is cold. That means no 12 volt to the Laycock solonoid valve. If the relay green pilot in your instrument cluster comes on then as you say it could be the overdrive itself. But check that it has 12 volt at the solonoid valve and listen to make sure it moves.

I had 2 black case relays and 1 blue case that do not work when cold.

As suggested by Art Benstein I replaced a capacitor in one of the black case relay. The markings on it is 100/25 Fraco which I took as being 100µf and 25 volt.

Under testing now the relay engages after about 5 -15 minutes after startup which is alright with me since I do not use OD when car is so cold.

I did not try any repair on the blue case relay because the 2 capacitors I can see are so small I am not clever enough anymore to do that precise work.

Thanks Art for the advice.

In my case the light does not come on until it shifts. I thought a switch on the transmission confirms the light.

I might as well have a weak capacitor but its takes someone like Art to drill down to find those details! Anymore, if Art speaks, people listen and feed back a thanks!

Another thing to note is there are occasions that I have found out that wires gets loose under the cap to that momentary switch. Sometimes I can move the shift lever around it will start working again too which clues me into looking under the cap.

I have come to the conclusion there are several manifestations or scenarios that can happen.

When it comes to the electrics or wiring of this year car, the electrics have a tendency to float to the top of suspicions.

Phil

''In my case the light does not come on until it shifts. I thought a switch on the transmission confirms the light.''

You are absolutely right, a switch on the transmission allows OD to engage only in 4th gear. When the green light is on the relay is giving 12 volts to the transmission solonoid valve. As you say I also ever noticed bad wire connections and also a worn/defective transmission switch some years ago.

I have an 86 that would not stay engage after it was nice and hot.
You know,like ran down the road for about ten miles and quit.
My impression was that the oil thinned out and it was losing push to hold the clutches engaged.

I tried using fresh fluid with Lucas trans fix added as per instructions. That is about a twenty percent mix. After that it stopped dropping out after being warmed up. Its a toss between lubricity and viscosity I think. I do recut the check valve seat plate when needed during oil changes too! A dimple shows up in that 60 degree angle. The ball and spring tension is not always centered evenly and I suspect there is leakage of pressure from the eccentric piston pump above it.

Some miles later it still works ok but has developed the cold symptom. It will not engage until I travel in it for about a mile or even a bit more if its a [cold?] which is hard to define within a California day. After that it is good for the rest of the day.

In my '78 242 GT owners manual, this was in their early years of using the Laycock overdrive, it is recommended to drive the car at least one mile before using the overdrive.
It was also mentioned that it was best to use the clutch as if you were clutching to pick up a regular gear shift. I have always done that unless I felt lazy on a long trip.


My other cars are still humming right along but I have also thought I still need to update the o rings in the '86. Its a wagon, usually well loaded and maybe the rings got hotter and harder sooner. I doubt starting at about 275 K and now 350 K is actually soon though.

In the recent months I have seen posts that address things like this going on in transmissions back East. If I lived back East, I would be the one without gears to get out and go! (:-)

Cold just affects "us old cogs" no matter what type of red fluid is running around in them spaces. (:-)

Phil

The '80 and earlier M46's don't use a relay. Current flows directly through the slide switch in the shift knob to the M46.

So you could try bypassing the relay by connecting the circuits together and depressing the shift button to see if it activates OD. If it does then the relay may be at fault.

--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

The devil, as usual, is in the detail. The 81- relay configuration uses a ground referenced lockout switch that won't be of much use without the relay. Be OK for testing, but don't get caught with a bypass engaged in reverse.
--
Art Benstein near Baltimore

Mahatma Gandhi, as you know, walked barefoot most of the time, which produced an impressive set of calluses on his feet. He also ate very little, which made him rather frail and with his od d diet, he suffered from bad breath. This made him ..(Oh, man, this is so bad, it's good)..... A super calloused fragile mystic hexed by halitosis. - ouch!

Are you sure it is the relay and not the solenoid?

Randy

No experience with this symptom, but if this map doesn't help you troubleshoot it, you could try replacing the electrolytic caps. That would by my first shoot from the hip guess.
--
Art Benstein near Baltimore

Two atoms were walking down the street one day, when one of them exclaimed, "Oh no - I've lost an electron!" "Are you sure?" the other one asked. "Yes," replied the first one, "I'm positive."