24V FFR Woes

[bfrieck]

I have a Series III 109 MOD FFR with the 24V system. The ignition system on the truck is 12v, however, and utilizes a 24v to 12v transformer to step the 24v to 12v. Anyway, the truck wouldn't run and my "mechanic" said he bypassed a "box" on top of the valve cover and everything worked fine. Well, I learned the hard way that what he bypassed was the 24v to 12v stepdown transformer. It worked for a little while until the coil got hot enough to explode and blow burning oil all over the engine compartment. I got the fire out without a huge amount of collateral damage but now I need to get it going again. Can I simply source a 24v to 12v dc transformer or is there something else I need to know?
Bruce

[I Leak Oil]

First step would be to fire your mechanic.....
You can find a replacement transformer or just convert the truck to 12V. Unless you need the 24V for something, converting is probably easier in the long run.

[JimCT]

24V coil

Not really a transformer since we are talking DC, but it should be easy enough to find a 24V coil

First step would be to fire your mechanic.....
You can find a replacement transformer or just convert the truck to 12V. Unless you need the 24V for something, converting is probably easier in the long run.

[I Leak Oil]

Converter then....

http://www.sportsimportsltd.com/24vdcto12vdc.html

[bfrieck]

What size converter do I need? The link sells all sizes (in terms of amps). The one in the truck is quite small with a small gauge wire going in and out so I'm assuming it's not a lot of amps. Any ideas?

BTW, mechanic has been fired - would prefer that he have been shot. 'Course I probably should have known better than to think simply bypassing something was okay.

Bruce

[bfrieck]

Would a 24 v coil be all I would need? Do the plugs and distributor innards care?
Bruce

[I Leak Oil]

Would a 24 v coil be all I would need? Do the plugs and distributor innards care?
Bruce

You need to find out what the converter was used to distribute power to. You can't assume that the wiring is original and it's all wired as it came from the factory.
From what little I know about the FFR stuff you should probably have 24V gauges and lights so this converter may have been an add on. In other words your truck may have originally all been 24V.
Perhaps the converter was being used to step the voltage down for the ignition coil which could be why it fried when it was given 24V. Don't know, just a possiblility.

You need to do more investigation as to what it is you have first.

[Boston]

What's your alternator putting out? I suspect 12v.
I'm thinking your truck was partly converted to 12v already. No better time, if I'm right than now to complete the conversion.

[bfrieck]

Thanks to everyone for their input. Here's what I know (or think I know). I bought the truck a few years ago when it had less than 7,000 km from the guy that imported it from S Africa. The odometer has always worked and the overall condition of the vehicle supports the mileage (kilometerage?). When I got the truck it no longer had the radio equipment but was otherwise all original military 24v FFR including the ignition system which consisted of the military distributor (heavily protected from causing interference with the radios - with screw in shielded plug wires), the military plugs (screw on connections); oem coil, etc. I learned from various sources including this forum that the oem ignition, and only the ignition (meaning coil, distributor, and plugs), was 12v instead of 24v like the rest of the truck (lights, gauges, two batteries, alternator (the great big one run by two v belts), the big (1-1/4" diameter) shielded conductors running from the alternator to the radios, etc.). I now know that the conversion to 12v for the ignition system took place in a little black sheet metal box (with louvers for venting) attached to the back of the valve cover on top of the engine. I learned that civilian plugs could be substituted for the super expensive and somewhat rare military spark plugs ($25 each from England), but doing so would require modifiying the military plug wires so they'd fit the civilian spark plugs or swapping the military distributor for a civilian one. I bought a distributor, plugs, plug wires, and a coil from our host, put it all together and everything worked fine for several thousand miles until it began cutting out and finally wouldn't run at all.

That's when I went back to my now-former mechanic who solved the problem by wiring around the little black (converter) box which resulted in 24 volts going to the coil and the resultant explosion and fire. The coil didn't get hot enough to detonate until I had driven about 5 or 10 miles around the ranch. Once the fire was out, everything 24v still worked including the starter which I used to load the truck on a trailer so I could remove it from the scene of the fire.

Back when I was exploring the "how to avoid buying $25 military spark plugs for every tune-up" issue, I seriously considered converting the whole truck to 12v but was dissuaded by forum members since, at that time, it amounted to a costly bunch of work to cure a bunch of then non-existent problems (the biggest of which is what to do about a 24v alternator or starter that has failed, neither of which had and still haven't).

So, except for minimal fire damage to other under-bonnet components, all I need is a 24v-12v converter and a new coil and I'll be good to go - I hope.

It occurs to me that if neither the spark plugs nor the distributor care whether they are fed 12v's or 24v's, it may be that a simpler solution is to replace the coil with a 24v model. That could be a problem if obtaining such a coil is problematic, but lots of vehicles have 24v systems so maybe a generic coil will work. Of course, that's a bit of a bodge for a future owner with ignition problems since unknowingly replacing a 24v coil with a 12v one will result in pyrotechnics. Does anyone know whether the distributor or plugs care what voltage they are fed? Likewise, what amperage will a 24v to 12v converter require?

Bruce

Bruce

[I Leak Oil]

If the converter is simply for the primary winding of your coil you can probably use the simple DC formula of V=IR to estimate your amperage requirement.
V is 12V
R is your primary winding resistance (3 ohm for example)
I will be your amperage requirement

Plugging in those numbers will yield a 4 amp requirement. This is JUST an example.

Note: The web site I copied was just the first one that came up when I searched on line for converters. I have no personal experience with that company. I would keep searching for the best deal and appropriate converter.

As for your other question, I don't know if the distributor and plugs care but I imagine it probably does make a difference.

[Les Parker]

In the past, I've hard wired from one battery (thus 12v) to the coil via a separate simple on/off ignition switch.
Alternatively, you could source something like this :-

http://www.sears.com/uxcell-5a-dc-24v-to-12v-car-power/p-SPM7556017511?prdNo=3&blockNo=3&blockType=G3

2p

[Thoma_s]

I also have a 24V FFR 109 petrol

The black box on top of the valve cover makes 24v to 10V for the coil.

Its a normal coil only its made not to make trouble for the radio in the truck. (Fitted For Radio)

You could use an normal ignition system after the black box.
Avoidinge to spend a lot of money on FFR spark plugs.

I would keep the 24V
Its just as easy as the 12 V

And you get better cranking in the starter motor, better lights.
The fire hazard with Lucas is probaly smaller. Higher voltage = lower current.

[disco2hse]

Reaffirming Thomas' call here and Jason has provided you with the calculation for the amperage requirements of your coil. Ignore any recommendations to 24V coils and such. With this, you can get a 24-12(10)V convertor but you will probably also need to use a ballast for the coil. The box (IIRC) also contains a surge protector and voltage regulator. It is likely that one or more of these components has failed in yours and it would be possible to simply fix it, provided the explosion didn't bugger it all up. In other words, you probably don't need to get a whole new box.

This link provides useful information: http://www.winwaed.com/landy/mil/military.shtml

Be warned, the FFR uses higher amperage than your usual Landie.

The alternative, as Les points out, is to take a feed from one battery that will be 12V. If you do this, it needs to be the first battery in the bank. I have done this. In mine, I have a charge equaliser between the two batteries. Therefore I have no box anymore (it was rubbish anyway). You need something there so you don't unnecessarily destroy good batteries.

So far as things like plugs are concerned. Your normal garden variety plugs and other equipment will work just fine. You are not going to be using military radio equipment (I assume) so you don't need to worry about noise suppression. Personally, I would take the opportunity to replace the points with electronic ignition (a la Pertronix, etc.)

[JimCT]

24V unimog coil

the convertors are not worth the effort

Reaffirming Thomas' call here and Jason has provided you with the calculation for the amperage requirements of your coil. Ignore any recommendations to 24V coils and such. With this, you can get a 24-12(10)V convertor but you will probably also need to use a ballast for the coil. The box (IIRC) also contains a surge protector and voltage regulator. It is likely that one or more of these components has failed in yours and it would be possible to simply fix it, provided the explosion didn't bugger it all up. In other words, you probably don't need to get a whole new box.

This link provides useful information: http://www.winwaed.com/landy/mil/military.shtml

Be warned, the FFR uses higher amperage than your usual Landie.

The alternative, as Les points out, is to take a feed from one battery that will be 12V. If you do this, it needs to be the first battery in the bank. I have done this. In mine, I have a charge equaliser between the two batteries. Therefore I have no box anymore (it was rubbish anyway). You need something there so you don't unnecessarily destroy good batteries.

So far as things like plugs are concerned. Your normal garden variety plugs and other equipment will work just fine. You are not going to be using military radio equipment (I assume) so you don't need to worry about noise suppression. Personally, I would take the opportunity to replace the points with electronic ignition (a la Pertronix, etc.)

[disco2hse]

the convertors are not worth the effort

woohoo, wave the placard :P

On the otherhand...