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01-18-2022, 03:25 PM | #1 |
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12v battery on 6v system?
I've had it with this weak 6v. I have the original 6v system on my 39 Ford Sedan. When it finally starts, it runs great.
Even with a new fully charged battery, the 6v barely turns the flywheel. Keep cranking over and over, then the solenoid starts smoking. I don't want to upgrade the whole system to 12v. Has anyone used 12v battery to start 6v systems? Still searching for timing and points adjustment instructions for 1939 Ford Sedan. |
01-18-2022, 03:45 PM | #2 |
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Re: 12v battery on 6v system?
I think the trick guys have done is use an 8V battery with a weak 6V system. I don't believe you can jump up to 12V battery with everything still being set up for 6V.
Have you checked all your grounds? I'd start there and see what happens. Also, are you sure your distributor, timing, carburetor, fuel delivery, spark plug wires & plugs, etc. is up to snuff? Hard starting could be caused by many other issues compounded into one big, hard start issue. Here is a link to a 8V battery: https://www.usbattery.com/products/8-volt-batteries/ |
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01-18-2022, 03:58 PM | #3 |
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Re: 12v battery on 6v system?
"Has anyone used 12v battery to start 6v systems?" - rayro39
Touch a 12 volt battery directly to the stater motor and ground. Make sure the transmission is in neutral and the ignition switch is ON....
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01-18-2022, 04:09 PM | #4 |
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Re: 12v battery on 6v system?
It runs great once it cranks over. New fuel tank, lines, fuel pump, rebuilt carb. I'm going to convert to electric fuel pump.
I am focusing on timing and points. I've never done those on a flathead v8. This isn't the crab style distributor. |
01-18-2022, 04:30 PM | #5 |
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Re: 12v battery on 6v system?
Clean ALL connections to a SHINY clean, then go with a 6V Optima and your problems will go bye bye.
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01-18-2022, 04:54 PM | #6 | |
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Re: 12v battery on 6v system?
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Quote:
Do yourself a HUGE favor and DO NOT use an 8v battery! DD . |
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01-18-2022, 04:56 PM | #7 |
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Re: 12v battery on 6v system?
Not sure it's [pertinent but, I remember (years ago) when I jumped my 6V battery with a 12V battery and the 6V battery exploded. with a big BOOM. i had done it many times before but, the last time was the "boomer".
Read all of this: https://forums.aaca.org/topic/297946...6v-with-a-12v/ Suggest you fix the problem the correct way. 8 V battery is a waste off $$$. Check your 6V battery to make sure it's fully charged. Try a new solenoid. Is your starter in good condition. Last edited by 19Fordy; 01-18-2022 at 06:08 PM. |
01-18-2022, 05:05 PM | #8 |
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Re: 12v battery on 6v system?
just my 2 cents worth 6v should be fine so i would get a multi meter and find out what's going on [this is one of the gremlins with 6v any voltage drop reeks havoc] but having said that well maintained 6v systems work perfectly well
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01-18-2022, 05:07 PM | #9 |
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Re: 12v battery on 6v system?
There was, and still is, a lot go cars, American, British, German etc. running around the world with 6 volt systems. There were issues with the electrics when I got my stock '46 Coupe. Slow cranking, dim lights, poor charging, but the problems were all corrected by cleaning connections to ground, replacing the battery to solenoid cable with the proper size, and having my generator and regulator serviced by a shop knowledgeable in old style generators. It starts, runs and charges just like it was built. To me, it would seem that changing over to 12V would be more work and more expensive, that going through the circuits and putting them back in good order.
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01-18-2022, 05:09 PM | #10 |
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Re: 12v battery on 6v system?
As 19Fordy said: "Putting 12V into a 6V battery can blow up the 6V battery. The hydrogen sulfide gas
goes BOOM!" Yeah, KABLOOEY! |
01-18-2022, 05:10 PM | #11 | |
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Re: 12v battery on 6v system?
Quote:
In response to your proposed idea, I like it. I've run my 47 for years that way, with only positive results. Rumbleseat Paul posted his way to do this, and I simply copied what he did with his 34. Hopefully you can find his old Rumbleseat notes somewhere. Briefly, I ran my 47 on 6 volts. The 12 Volt battery was separate, and a 'total-loss' affair. It would need a recharge every few months - no 12V charging done with the car. (Small 12V battery, 80 Fairmont, I think) The starter was the ONLY thing that ever saw 12V. The rest of the car ONLY saw the original 6V. Like Rumbleseat, I would always attempt to start on 6V. If there was no quick response, then I would hit the 12V button. It never failed. Thanks to Paul for a great idea. (Should probably add... On my 34, I did the total assembly of that car. As such, I handled each and every wiring connection. So, it was all fresh and clean, with proper size wires. That car functions fine, as it should, on 6V. The only issues I had, were (1) a good battery, and (2) a good starter - took two tries to get a good starter. So, my point being, like others have posted, should be able to make your 39 work good, if you wade through all the subtle troublesome areas. My first guess - if wiring issues are good, then I'm thinking, starter - because you say 'barely turns the flywheel'.) (Something to think about, because I almost never see it mentioned... How about that starter solenoid (switch)? It has to carry to full starting current, perhaps 150-200 amps. How old is that thing? Original 1939? Have you measured the voltage drop across it? I only mention this because I have a 96 Ford with 300K miles on it. I recently had starting issues, and found that the switch was 'tired', and had developed a voltage drop across it. Check your voltage drops - should be able to see almost cranking voltage at the starter, same as cranking voltage measured at the battery. ie, no lost voltage from battery, to starter.) Last edited by bobH; 01-18-2022 at 06:13 PM. |
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01-18-2022, 05:27 PM | #12 |
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Re: 12v battery on 6v system?
ixnay on the 8v.....I depend on my test motor which languishes in my unheated barn
12mo per year. I use a Walmart 6v battery and big fat cables....minus 6 last week end and she fired right up both days just ask my neighbors. Charlie ny |
01-18-2022, 05:32 PM | #13 |
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Re: 12v battery on 6v system?
On a 39 Ford you hook one jump cable battery to the side of the solenoid , the one that goes down to the starter , the other cable goes battery to head bolt ,with key on just touch this to throw the starter ,,battery can be wired x to neg or neg positive ,Mines a variation of Pete Hoovys
Last edited by FlatheadTed; 01-18-2022 at 09:47 PM. |
01-18-2022, 06:33 PM | #14 |
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Re: 12v battery on 6v system?
Plenty of farmers growing up used an 8v in their 6v tractors. Certainly worked then. I still say find the issue. Re-reading your post, you could install a 12v just for starting, but that sounds a lot more complicated than finding the issue.
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01-18-2022, 06:55 PM | #15 |
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Re: 12v battery on 6v system?
X2 on post 12. If you do it make sure you have plenty of spare bulbs because you will need them. Most of the old tractors 6volt did not have working lights.
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01-18-2022, 07:34 PM | #16 |
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Re: 12v battery on 6v system?
When I bought my second '39 pickup it had an 8V battery in it. I cleaned connections up as stated in other posts, went through the ignition system and put in a 6V optima. With 8V and dirty/old cables and connections it started quite slowly but now starts immediately. I have been pleasantly surprised given the trouble I have heard people have with 6V - don't give up on it!
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01-18-2022, 09:52 PM | #17 |
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Re: 12v battery on 6v system?
To have a 12 volt just for starting wire in another solenoid on the starter side then to the 12 V ,and a ground ,this would be a total loss ,you could add a Alternator on the back wheel like Lawrie does on his Caravan ,
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01-18-2022, 10:50 PM | #18 |
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Re: 12v battery on 6v system?
There used to be a "6-12" battery - two 6V units switched by a solenoid so that you had 12V to start and went back to 6V to run. It solved the weak cranking problem when my old '42 wagon's flathead was hot.
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01-18-2022, 11:06 PM | #19 |
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Re: 12v battery on 6v system?
Theres got to be something wrong if that 39 cranks slowly on six volts. My 39 Deluxe is all stock and that starter spins the flathead plenty fast on six volts. Faster than the 52 Merc. I've used 12 volts to start the Merc but straight to the solenoid, by-passing the rest of the car's electrical system.
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01-18-2022, 11:08 PM | #20 |
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Re: 12v battery on 6v system?
as your vehicle runs well once running, the problem is in the starter motor circuit. Could be any or all of the following; starter needs rebuild, insufficiently sized cables, bad ground connection[s] from starter to block, block to chassis, chassis to battery, dirty connections anywhere else [bat to solenoid, solenoid to starter, even within the solenoid]....
The solenoid smoking would be a good place to start, there is obviously high resistance; lotsa heat there.
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