No overdrive at night?

Mike51Merc

Mike51Merc

Well-known member
OK Borg-Warner overdrive gurus here's one for you:

First, this is a 51 Merc on 6V positive ground with the standard BW OD system. This problem has been bothering me for a few years. It seems that my overdrive doesn't like to upshift at night, particularly when I'm on my way home :mad:. It usually works fine until I stop at a toll or red light and then it fails to upshift. The next day everything is fine.

All connections, contacts, wires, and relays are good. I can see the solenoid "load" the system through the ammeter at the appropriate speed, but she won't upshift. I even installed a jumper wire on a toggle switch to manually override the relay and governor switch, but that didn't help.

The solenoid bench tests fine. Is it possible that the engagement coil gets hot and loses magnetic pull? Is it possible the ****** gets hot and binds the pawl? Is it possible that the headlights draw down so much current that there isn't enough left to throw the solenoid? I also have a new 780 CCA battery and my ammeter shows the system is performing well. The only time I show discharge is when idling with the headlights on.

Any experiences and suggestions are welcome. I'm also posting this on Shoebox Fords.
 
If it was something with heat wouldn't it happen during the day too? Low voltage because of headlights sounds like the right direction to me.
 
Yes...find someplace you can drive fairly safely without lights and turnemoff...or, much more sensibly, turn on the lights in daytime and see what happens.
 
I had the same thing happen this summer. OD would not kick in, next day it worked fine?? About 4 weeks later the battery went stone dead over night, with nothing left on....... Battery was shot and would not take a charge at all. Replaced the battery and so far not problems........
Good Luck
 
The charging system is a typical 6-volt system. It is taxed more while the head lights are on and after a long stop with the brake lights even more. You may have a battery getting weak as was mentioned earlier or you may have an internal short in your shift engagement solenoid. Some internal coil shorts can be near the end of the coil and will only weaken it not kill it completely. If you can find another "known to be good" shift engagement solenoid, you might put it on there and see if that does the trick. That or try another battery.

Kerby
 
Thanks for your insights. The battery is 9 months old and shows no sign of weakness. Does anyone think I should mess with the regulator to pull more voltage out of the generator, or is that asking for trouble?

I'll probably end up getting another solenoid, but at the price they come I'd hate to end up changing it needlessly.
 
Mike,

It could very well be your relay - same thing happened to me. Pretty easy to try a fix to the relay instead of spending the big bucks on a solenoid.

Make sure all your connections on the relay are clean. Look at the back of the relay. See the rivets in the picture? Two at the top, two at the bottom, one on the lower right but NOT the insulated one on the upper right. These need to make good contact with the metal straps - sometimes they build up corrosion underneath. Clean them good and spread some solder from the rivet to the strap and you may improve the connection.

My relay used to start clicking after running quite a while, then the solenoid would drop out. The cleanup/solder trick has worked for me for the past two years. Learned this from an OD expert in Colorado named Bernie Sawin.

Good luck.

Ken
 

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Is it possible that you may have used the choke at night, and maybe not pushed it all the way back in. This will put your carb on a fast idle setting , which will cause the OD to not engage even though the solenoid is fine. The enine has to go on compression instantaneously for the gears to engage. I've had this experience several times, but am now wise to it ! OLD AGE bites !! bill
 
Merc Mike, could you possibly have used the choke and not have returned it to full off ? This will leave the carb in a fast idle condition which will sometimes not allow the overdrive to engage . The engine has to momentarily go into a compression mode in order for the gears to engage. I personally experienced this....more that once ! My wife even has to remind me occasionally....damn ... that hurts !! bill :mad:
 
You have a high resistance connection somewhere in the system.
You may have to take every connection involved apart and check for corrosion..Check for loose wires in crimped connectors also...If loose, restrip and crimp new connector on or restrip and solder.
It worked when it was new so the only thing different now is old age and corrosion.
Put a voltmeter on the solenoid and see what is happening when it is off and then on...With the system charging you should have at least 6 volts there.
 
Exact same thing was happening to my '50 Ford - I was in process of re-wiring my car a little bit at a time due to money issues. So I had checked all the contacts from the relay down to the solenoid and everything looked OK, but would still not engage with headlights ON after driving for a while. So what I ended up doing was replaced all the connectors at the relays and solenoid and that fixed it. The solenoid pulls 30 amps to engage so the wiring and connectors have to be deadon to operate.
 

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I agree with Kens36 & Pete.. but go one step further, remove the lid from the relay and clean up the points with a point file, clean the fuse bar down to clean copper and solder as per kens36, then remove the solenoid and pull the lid off and clean the file points and degrease it, then make sure all the wire connections are good and clean as per pete. this won't take that long to do and you will have a o.d. that will make you happy for a long time. as for the voltage regulator adjustment look at a old motor manual before atempting this, you can mess one up in a heartbeat. keep us posted on your o.d. repairs...jdl

p.s. most o.d. problems are electrical and most will show up in real hot weather, so it is best to fix all this if you plan a hot weather trip, nicer to work in your garage than on the road.
 
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Blu Dice said:
Exact same thing was happening to my '50 Ford - I was in process of re-wiring my car a little bit at a time due to money issues. So I had checked all the contacts from the relay down to the solenoid and everything looked OK, but would still not engage with headlights ON after driving for a while. So what I ended up doing was replaced all the connectors at the relays and solenoid and that fixed it. The solenoid pulls 30 amps to engage so the wiring and connectors have to be deadon to operate.
Click to expand...

Hey Blu Dice...your car sure brings back some good high school memories (1954). Except for the license plate location, we could be twins. (sorry for the small pic...sign of the times). :)
 

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Thanks again guys. My connections are good, clean, and tight. Brand new 12 GA wires and terminals, new kickdown switch, new battery.
 
If you ever check out the old engagement solenoids you'll find they have two coils in there. One has heavy windings for rapid engagement and the other has fine wire windings to act as a holding coil and not use so much juice. If I remember right one set of points in there is to engage the holding coil and the other is a path for the ignition cut out during kick down operation. Both those points sets need to be clean and functional for good operation.

Kerby
 
It's been a while since I fooled with overdrives, but here goes:

LOT of electrical problems can be traced to a bad ground. How about temporarily running a wire from the case of the solenoid to the positive battery terminal? That would eliminate everything in the ground part of the circuit. The wire would need to be pretty heavy if the solenoid draws 30 amps.
 
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