1955 used 12v battery on 6v car

MarshallTucker

MarshallTucker

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Sep 12, 2023
Thunderbird Year
1955
I installed a 12volt battery in my ‘newly acquired’ 1955 Bird.

Total screw up……maybe. All seems ok, except the wipers are now constant on. I don’t know of anything else….so far; had the car only 3 days now.

Seeking comment on what damage I most likely caused and also what I need to consider now?

White smoke poured out from under the dash while cranking with the 12 volt batt installed. The engine did run for about 15 seconds then puttered out. Now I can‘t get it to start (I have installed a new 6 volt batt).
 

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You can start by pulling the dash and repairing the burnt wires. Big help. You may need a new voltage regulator, depending on how long it was hooked up. Possibly have to replace the condenser, but they are pretty tough.
 
You will have to check the entire wires of the electrical system. What you described you might have burnt a few other things. Installing a 6 volt is too late, The damage is done.
 
At this point, I would be looking at a complete changeover from 6 to 12vdc. It isn't cheap but it is probably the best thing you could do to make the car road worthy. It involves a new starter, alternator (instead of generator) electronic ignition (Pertronics), new bulbs everywhere, if you have electric windows and seats, they will move much faster but should be OK on 12 v. figure 1500-3000 but you are well advised to do this now that you damaged much of it and will have to work on it anyway.
 
Everything runs on smoke so once you let the smoke out nothing works anymore! If you want more cranking power and brighter lights you can go with an 8vdc battery but NOT 12vdc! You now have a big project on your hands. Like mentioned, might as well do a rewire.
 
MarshallTucker said:
I installed a 12volt battery in my ‘newly acquired’ 1955 Bird.

Total screw up……maybe. All seems ok, except the wipers are now constant on. I don’t know of anything else….so far; had the car only 3 days now.

Seeking comment on what damage I most likely caused and also what I need to consider now?

White smoke poured out from under the dash while cranking with the 12 volt batt installed. The engine did run for about 15 seconds then puttered out. Now I can‘t get it to start (I have installed a new 6 volt batt).
Click to expand...
Remove the battery and don't reinstall one until you've found and repaired all the damage.
You'll need an original wiring diagram for the car some tools (test light, multimeter, etc.) and a knowledgeable assistant.

A '55 T-Bird does not have a fuse box. That can make electrical troubleshooting a bit more challenging.

The dash gauges aren't voltage or polarity sensitive. You may have fried the clock and/or radio. Any previously damaged wiring may now be beyond repair.
Removing the dashboard is a large project, but you may only need to remove the gauge cluster and seat to gain better access to affected wiring under the dash.
A previous owner may have installed a conversion / electrical windshield wiper motor. It may be where the smoke came from, if the switch for it was turned on..

The first order of business is correctly diagnosing the problems the car has now. It will save you time, money and aggravation rather than blindly throwing pricey parts at it, that may not solve a problem.
You may need the assistance of an old-school automotive electrical shop, or a specialty Thunderbird shop.
 
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You can get the electrical manuals for $30 from Larry's. If you want, I will send you my XL spread sheet of parts and sources. '55 was the last year they did 6V. '56 started the 12 v. Rewire will have a fuse panel and it sounds like you should not try it yourself.
 
Since the wiring harnesses are probably toast. Find a garage that specialises in antique car restorations. Do not try yourself. This will cost you $$$$$. A expensive lesson learned .
 
While many here will steer you to a restoration shop or other "professional", I highly recommend reading a good repair manual and tackling the job yourself. These cars are really simple. They are not the computerized disasters like today's cars, you really can fix this and gain a real understanding of what soon will be your favorite car.
 
Don't forget that 6V wiring is designed to carry more current than 12V wiring. It can handle 12v unless there was a dead short. Also the 6v Thunderbirds are Pos ground and not Neg ground.
 
MarshallTucker said:
I installed a 12volt battery in my ‘newly acquired’ 1955 Bird.

Total screw up……maybe. All seems ok, except the wipers are now constant on. I don’t know of anything else….so far; had the car only 3 days now.

Seeking comment on what damage I most likely caused and also what I need to consider now?

White smoke poured out from under the dash while cranking with the 12 volt batt installed. The engine did run for about 15 seconds then puttered out. Now I can‘t get it to start (I have installed a new 6 volt batt).
Click to expand...

There isn't much you can ruin in these cars with the 12 volts but the radio and light bulbs If you didn't turn any lights on then none of them should have been hurt. Ditto for the radio and odds are high the radio didn't work anyway.
As to the white smoke from the dash, what I suspect might have happened is you burned out the clock or one or more of the gauges (fuel or temperature), there's not a lot of stuff under the dash that gets power.
As to the engine running and then not running, possibly the coil burned out or the ballast resistor burned up so now you are not getting spark.
 
No ballast resistor on 6volt cars, but the points could be BBQed.
 
MarshallTucker said:
I installed a 12volt battery in my ‘newly acquired’ 1955 Bird.

Total screw up……maybe. All seems ok, except the wipers are now constant on. I don’t know of anything else….so far; had the car only 3 days now.

Seeking comment on what damage I most likely caused and also what I need to consider now?

White smoke poured out from under the dash while cranking with the 12 volt batt installed. The engine did run for about 15 seconds then puttered out. Now I can‘t get it to start (I have installed a new 6 volt batt).
Click to expand...
Wiring should be fine. Smoke from dash radio, clock. Generator and regular may be bad. Coil points and condenser should be changed. Put a new 6V Battery in it positive ground (+) is the ground. Turn the key on no smoke then try and start. If starts see what doesn’t work if not start with coil and refer to above . Check the gen light and oil lights they should be on before you try and start. If not replace them if they are on try and start the car. Folks have been jumping 6V cars with 12 volts since 12V became the norm.
 
Brax said:
Wiring should be fine. Smoke from dash radio, clock. Generator and regular may be bad. Coil points and condenser should be changed. Put a new 6V Battery in it positive ground (+) is the ground. Turn the key on no smoke then try and start. If starts see what doesn’t work if not start with coil and refer to above . Check the gen light and oil lights they should be on before you try and start. If not replace them if they are on try and start the car. Folks have been jumping 6V cars with 12 volts since 12V became the norm.
Click to expand...
Boy, would that make the starter spin..
 
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