Overdrive Tune-up

JT FORD

JT FORD

Senior Member
After having trouble with the '49 not always going into OD I got it on ramps and went to work. Removed the solenoid on the convertible, not real easy but do able. Filed the points, sprayed it down with electric tuner cleaner. Tested on the fender with the car battery and it worked just fine. Test drove and it wouldn't kick in! Tested all the connections on the relay and the wire on #4 post on solenoid and all tested over 6 volts. Finally run a heavy jumper wire direct from the battery to the
ignition connection on the relay and it worked every time. The wire that was feeding the relay from the ignition switch didn't have enough power to handle the throw in amps. Sometimes it would work and sometimes it wouldn't.
My question is: Can these switches go bad after 65 years? Not sure how to test it in the car. What would be wrong with putting a # 12 wire from the starter solenoid on the battery side to the power feed on the relay and forgetting going through the ignition switch? I checked the governor with a light in side while driving and it comes on a about 31 mph and goes off at about 23 mph. I know the wire would be hot all the time but as soon as the car stops the relay is dead.
 
I'm glad you found the culprit. There is probably no harm to feed off the battery as you propose. I personally would feel better about the safety of the car in storage/garage knowing all electrical connections were as safe as possible and dead with the switch cut off. There is still a problem somewhere that can be corrected to work as original and it shouldn't be hard or expensive to repair. All that is left is the ignition switch and the wire to the relay. At a minimum, I'd consider a relay in the feed wire from the battery that is triggered by the switch.
 
Kahuna said:
40coupe has the answer. Add a relay.
Click to expand...

Sorry, but you're suggesting that a relay be added to a system that already has a relay. Belt and suspenders.

To the OP, #12 wire is a bit small for this application. I had a similar problem and my solution was simply a #10 wire from the ignition circuit to the OD relay. The #12 wire was allowing too much voltage drop, and it seems that anything less than 6 volts will fail to throw the solenoid into OD.

As for your voltage checks, my problem only occurred at night with the lights on, and then often after driving a bit at low speeds. Under those conditions, the battery tends to drain off a bit because the generator can't keep up the charge at low speeds. Test the voltage at the battery and then the voltage at the OD relay. There shouldn't be much of a difference, if there is, try again with a heavier feed wire.
 
Mike51Merc said:
Sorry, but you're suggesting that a relay be added to a system that already has a relay. Belt and suspenders.

.
Click to expand...

Sorry, but the additional relay is there to switch the hot wire that he has added from the battery terminal to the OD relay. This is so it can be switched with the ignition without putting the whole load of the solenoid on the ignition switch. It is not belts and suspenders.
 
Check the fuse holder clips on the OD relay! They are riveted on they tend to work loose and cause resistance resulting in a voltage drop to the system.i soldered mine .Phil
 
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40cpe said:
Sorry, but the additional relay is there to switch the hot wire that he has added from the battery terminal to the OD relay. This is so it can be switched with the ignition without putting the whole load of the solenoid on the ignition switch. It is not belts and suspenders.
Click to expand...

He wanted to bypass the ignition switch entirely and have a permanent hot lead to the OD relay. Anyway, the OEM system was designed to handle the load of both the ignition coil and the OD system through the ignition switch. If it was inadequate, then you might consider a relay, and like some instances, like upgraded high wattage headlamps, a relay can save your headlight switch from early failure.

Belt and suspenders. Some guys just like relays, sometimes with relays even controlling other relays. I've seen engine compartments stocked full of relays and 95% of them were unnecessary. To me they're just another potential failure site. This coming from a guy who has seen quite a few relay failures in modern cars, motorcycles, and snowmobiles.

Now, I wouldn't permanently hot wire the OD, but I did add a manual override toggle switch to my OD that hotwires the solenoid on demand. That doesn't have a relay either.
 
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I like relays. My thought was to relieve the old ignition switch of the load.
Oh well
 
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Kahuna said:
I like relays. My thought was to relieve the old ignition switch of the load.
Oh well
Click to expand...

Sorry if I came off as rude. To me there's no reason why the car can't be brought back to OEM specs and run normally as designed. And---- I guess I have a thing against relays and overcomplicating simple old systems with modern-day stuff that isn't really needed.
 
I think the OD can be made to run as it was when new. Maybe a new ignition switch will do it? Hate to spend $70. and that doesn't do it! I don't know if the switch gets old and will not carry the amps to kick it in? Henry should have made that relay a "real" relay and added another post on it that ran straight to the battery after the switch activated it. That is how my headlights are wired now.
My idea of running another wire from the battery will run it with more power. I have tested the govenor with a light inside the car and it works like it should. With the car shutoff there is no power to the relay or the solenoid. And, there shouldn't unless the govenor descides to go for a speed some night!

I am going to make up a wire, it could be 10 gauge and keep in the car in case I am off a ways from home, like Minn. at the Central National meet and I want that car in OD. After having OD its a pain not having it all the time. I've had 4 of these Shoeboxes and they all had OD this is the first one I have had a problem with. Anyway thinks for all the advise. One thing I will do if it acts up again is replace the original wire from the switch to the relay with a heavier wire.

JT
 
You will gets lots of "opinions" and "advice" here. Sometimes it it hard to sort the wheat from the chaff. Do what you think best and you will be fine. I agree that it would be highly unlikely that the OD rely would energize while not in motion with your plan. Maybe since you cleaned the OD solenoid it will work fine anyway.
 
JT,
When I was having my OD problems it was usually after dark returning from some cruise dozens of miles from home. Usually I was unaware of the problem until I hit the interstate stuck in underdrive. Very frustrating.
At first I started carrying a jumper wire with alligator clips, then I did a semi-permanent toggle switch (from the solenoid terminal on the OD relay to the heavy voltage regulator BATT lug) to manually throw the solenoid.
When I finally found the problem was voltage-drop, I fixed it but kept the toggle switch there just in case.

Also, if you open the canister of the OD relay, there's a set of contact points in there atop the relay coil that should be cleaned and gapped.
 
There are two sides to a circuit in a car.....the hot feed and the return thru a ground. The advice above about checking your wire connections is all good including having a #12 gauge wire for the OD wiring. What I haven't read is to check your grounds.

The OD system grounds both the solenoid and the governor through the transmission....thru the bell housing.....through the engine block.....and then back to the battery by way of the ground strap. If ANY of these points of contact is loose, dirty, rusty, or your engine ground strap is corroded, you will lose voltage in the overdrive control circuits. Same with the solenoid and governor.....clean metal-to-metal contact from these components to the trans housing are very important.

Unless you plan to separate all your trans-bell housing-engine connections to clean and restore a good ground, I recommend installing a separate ground wire back at the transmission. One of the solenoid mounting bolts to the body under the car with a #10 or heavier wire can provide the consistent grounding you want.
 
All good ideas here. The relay was replaced with a new one from 5th Ave. in Kansas last year. Mac VP's comment on grounds is another thing to check out.

If with every thing factory stock now it may not fail again. But, if it does I will
go back under the car and use one bolt on the solenoid to attach a ground wire to the ******.
 
Check the kickdown switch under the gas pedal. the one in my mercury was all corroded and giving me the same problem
 
Yes, ignition switches will cause a voltage drop due to loose contacts from years of use.
The best way to check is to check the voltage at the Batt. side or input of the relay. It should be the same as what your battery is putting out. Also what is going in to the relay, should be coming out. 6V in 6V out. I have found many relays that had a voltage drop due to as Trainguy said, loose contact at the fuse holder. Also under the relay cover all contacts are held by rivets that over the years become less conductive. I solder all these connections. Another thing that really helps these OD's is to change the generator to a 6v Alternator.
 
One thing I've thought of is the generator never seems to put more that 6.5 volt., Some say it should be closer to 7 volts. That would probably help to get alittle extra. What do people think of that? By the way the relay was new last year.
 
I have a similar problem with my '52. It worked just fine, but after I hit a bump in the road quite hard, it wont go into overdrive. It freewheels, but the overdrive gear doesn't engage. I checked all the wiring, but it's all good. Other than the overdrive not engaging, everything else is the same. Maybe a mechanical problem?
 
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