800 Gas, complete conversion to 12V Neg. gnd

bvilten

New User
Hello All,

Thanks for taking the time to read this, and for the help if offered.

I consider myself relatively competent as a mechanic (Just completed a full engine swap on my Envoy) But my knowledge is lacking in electrical. I am trying to convert my 800 completely to a 12 volt system with a negative ground. If it is not really beneficial to go that far I am willing to listen. I have found various kits but they all seem to not include something can you recommend a good kit? Also what other components will need to swap out, I assume the amp meter, tach, and perhaps the oil gage, I have a coil that claims to work for 6 or 12, there are some components (little square boxes) attached to what would be the fire wall on a car. I have no idea what they are for. Do I need a new wiring harness?

I thank you for any help you can offer.
 
The question is why switch. The reason I did my 640 is it was not charging when I bought it, which I knew. Between the cost of new 6 volt parts and not being able to jump start at 6 volts if ever needed, I decided to switch. I also had a spare battery on hand. The 6 volt starter and solenoid runs ok on 12, just don't crank it for too long. The kit to me was not worth the money since I could rewire it myself along with fabbing the 2 mounting brackets. All what was really needed to buy was the alternator. I wasn't crazy with putting a Delco product on a Ford, but that's the straightest route. Now, which alternator: there are basically 2 types; 1 wire and 3 wire. My take is the 3 wire will start charging at a lower RPM, the 1 wire is easier to wire. I went with the 3 wire. There are many places on the net that cover this topic better than I could. The wiring is very straight forward. Just watch the wire sizes and don't use all the same color!

There are many more details which I'm sure others will chime in. Hope this helps.
 
The "tach" (proofmeter), oil pressure gauge and temperature gauge are probably all mechanical on your tractor and won't need to be changed out. I believe the fuel gauge will need to be changed, and maybe the sending unit. (Mine doesn't work and I've never bothered to try to fix it.) If you have an ammeter, I suggest replacing it with a voltmeter, as it's simpler to hook up and you really can't correctly wire the ammeter with an alternator.

One of the "little components" is probably the ballast resistor for the coil, which I'll get to in a bit. You might also have a six volt regulator that would allow you to use the original fuel gauge.

Here's the deal with coils: Most "six volt" and "twelve volt" ignition coils are the same. When a ballast resistor is placed in series with the original six volt coil, it will work on twelve volts. The alternative is to get a coil intended for 12V conversions and has internal resistance such that no external ballast resistor is required. These are typically labeled "12V no external resistor required" while the more common coils are labeled "12V external resistor required". There are pros and cons to either approach, but they both will work.

One additional part that needs to be changed is the starter solenoid. You need a solenoid from a diesel hundred series tractor. Note that there are 12 volt solenoids for later Ford tractors that DO NOT WORK and will cause the starter to crank as soon as you hook up the battery. And of course if you have lights, those will need to be changed out as well.

The wiring for an old tractor is simple enough you can probably do it yourself. You can find numerous articles on this site on twelve volt conversions by googling "12 volt conversion site:yesterdaystractors.com". But if you're not comfortable doing it yourself, buy a ready-made harness. You might still have to modify it for your particular conversion, though.
 
I am in the process of doing my 850 right now, and bought the kit from this site, hard to beat, the usual Chinese stuff, rebuilt 1-wire, correct pulley, correct brackets, wiring harness, ballast resistor and new belt for $99. Only problem so far is the holes on the main bracket are just a touch off, alt is just a bit to the rear, just need to trim the holes to get the belt lined up. It's also pretty easy to just use a 12V car solenoid so you can run the full 12V jumper from the solenoid to the ballast resistor for better starting. Would be done by now, but once I got the Wagner loader pump shaft out, went ahead and got a new PS belt as well, and then discovered that someone had put a non-PS lower radiator hose on it, and the old belt had almost sawed it in two.. Also got the upper hose while I can get my hands in there, and also a new gas tank valve. Is much more difficult doing it with the loader on there, would be a breeze on a bare tractor. The old exhaust was a little cheesy, stock type muffler but the down pipe was cobbled up, but since it has the loader, I am going to install a 2-1/4" Corvair Turbo-type muffler with an up-pipe, never cared for the underhood muffler right by the carb and fuel line. That muffler fits nicely between the tubes of the loader, and adapter and a couple elbows gets it done
 
The standard question is if it ain't running on 6V what makes you think it will on 12V? It is a fact that 99.98% of all non-starting/non-running issues are due to mucked up wiring systems. The OEM FORD 6V/POS GRN setup is one of the most misunderstood and often hack jobs done. There is nothing wrong with converting to 12V/NEG GRN, if done for all the right reasons, and when done correctly. You don't change out all those items when doing a 12V switch over. OIL and TACH are mechanical devices, not electrical anyway. Some swap out AMP Gauge for a Voltmeter but I prefer to leave the AMMETER too. Get a true 12V coil -don't guess -a 6 & 12 unit is BS. You said: "...there are some components (little square boxes) attached to what would be the fire wall on a car...". That would be the Voltage Regulator. It is used with the generator AND both get removed when doing a 12V job. I suggest you get the Essential Manuals before going any further. The OEM Owner/Operator's Manual, the CLYMER I&T FO-20 Manual, and a 53-59 MPC are important, necessary tools. Start with what is OEM and work with that. Disconnect battery, get tested at a trusty shop, if bad replace with a new good (6V or 12V) brand, and avoid cheap bargain types. Don't buy any new parts until you know old is defective and if you really want 12V. If so, in addition to a good battery, you will then swap out genny and VR and need a good 12V alternator (DELCO 10SI typical), a tested 12V coil, and an optional new wiring harness. Old will work with modifications. Alternator needs a new belt, belt tension bracket, and cables need to be 12V style. Do not connect battery power whether 6V or 12V until you verify the wiring is all correct. I also suggest you rebuild the distributor preferably before you switch over to 12V. You may find the cost of a 12V switch over will be more than a basic problem solving method on the OEM 6V, and, less hassle. You need to evaluate your needs. A part time user or a daily user? Myth #1 is 12V start better in cold weather. 12V spins faster yes, but 6 or 12 if not maintained correctly will result in problems. Use of more than a few weeks at a time will deplete specific gravity, the biggest killer of a battery. A good battery float charger (NOT a trickle charger) is highly recommend to use when tractor is not in use. DELTRAN Battery Tender is a good reliable brand. You have a lot to think about and a lot of technical reading to do before you start. It's is your tractor and you can do what you want. I rebuild distributors, generators, starters, carbs, and more if you want more help -my email is open. If you decide to go with 12V I will buy your OEM generator and Voltage Regulator. One last detail, I suggest you disconnect the lights when verifying the electrical system. Lighting is often a ho-made project and many are done haphazardly. Additionally, if you have 6V lamps now, and will be doing 12V switch out job, you will need 12V headlamps as you will let the smoke out of the 6V lamps the second you ignite 12V power.

FORD NAA, 600, & 800 ELECTRICAL w/TIMIMG:
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FORD 600-800-900 12V SWITCHOVER:
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FORD OEM 600/800 OWNER-OPERATOR?S MANUAL:
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Tim Daley(MI)
CLYMER/I&T FO 20 MANUAL
 
Thanks for the help and tips,

My tractor is running. I want to switch it over because 12V Neg. is where my experience is. You are right as far as I am concerned that the 6V Pos. Is a mis-understood beast. My chargers, jumper packs, etc are all 12V. I have the OEM Manual but I will look for the other books you mentioned and give this some more consideration.

Thanks again.
 
I'm not sure exactly what you mean by "complete conversion". If you switch to a 12 volt battery and a 12 volt alternator, the everything will be running on 12 volts. There is no "partial conversion" unless you still have a 6 volt battery in the tractor alongside the 12 volt battery.

Once you've converted the battery and charging circuit to 12 volts some other things, like the headlight and tail light bulbs, will need to switched out for 12 volt equivalents or they will fail in short order. Other things, like the starter will not need to be touched as a 6 volt starter runs just fine on 12 volts. If you keep the original 6 volt coil then you will need to add a ballast resistor in line with the coil, but the rest of the ignition circuit doesn't need to be altered.

As MarkB said, the gauges and their senders may need to be swapped out. I am not 100% sure, but I don't think that he is correct about needing to swap out the starter solenoid as I am reasonably sure that the original 6 volt solenoid will work fine with 12 volts.
 
It is your tractor and your time and money so you can do whatever you want. There is no "beast" involved with 6V/POS GRN. It's a pretty straight forward basic design. One has to understand simple electronics a bit but it isn't difficult to comprehend if you are not savvy with electrical systems. Machines will on 6V NEG GRN too. Just because you have a 6V battery doesn't mean it HAS to be POS GRN. It was just the way engineers developed the system. POS GRN had to do with applying a faster, hotter spark. Starter motors don't care if 6V or 12V and they along with the solenoid are just fine on 6V with a 12V switchover. A 6V POS GRN system CAN also be jump started with a 12V NEG GRN vehicle too. You only need to know the correct procedure. Jumper 12V - NEG source to 6V starter solenoid NEG battery cable connection, apply + POS 12V source cable to any metal ground on tractor. Be sure to stand clear and that tractor engine is in neutral safety starter gear. Unit will get hot fast so do not leave cranking for more than 8-10 seconds. If a jump won't start it, there is something else wrong. As stated, 12V is fine for all the right reasons: Spins the starter faster, brighter lights, can run 12V components like sprayers, winches, and 8-Track Players. The #2 myth about 6V is that it is harder to start in cold weather. If an engine is old and worn, any system will cause harder starting. I and many others have had no issues starting our 6V systems in cold weather. The key factor for any machine is PM (Preventative Maintenance). I can't emphasize enough that it doesn't matter which electrical system you are using, if the wiring is not correct, there will be non-starting and other issues.

Tim Daley(MI)
 
OK, got mine fixed up and running great. Someone in the past had done a nice job of rewiring the 6V generator and regulator, but the PO had thrown a 12V battery in it at negative ground, so when I corrected it and polarized it, no workee. Pulled all the old stuff out and tidied things up. Alternator works properly, and all the original guages work. At first I wired it to work with the 6-volt solenoid and push button, but the starting lug on the solenoid went dead after a bit, and I wanted to have a key on it anyway, so I went ahead with the 4-post solenoid, and had a new key switch for a later tractor that fit the hole on the left side of the dash perfectly. Used a TSC 4-post solenoid for a 65-up 2000, 3000 etc because I had one, works the same as a car solenoid, and gives me a source for full 12V jumper to the coil side of the ballast resister. I prefer the car-type setup as it works very well, and one spare solenoid fits most of my junk. Maybe I'll use the push button to hook up a horn lol. Spins fast and starts very well, also helps that it now has the correct and fresh carb on it, someone stuck an 8N carb on it, which was completely full of rust inside- and it started! Very responsive and strong like it should be. Group 35 battery fits very well, and in stock at TSC. Unless you have a restoration- type deal, the 12V setup just works better and is simpler all the way around
 

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