Rosscommon 12 volt conversion opinion

[Nate475]

I finished the Rosscommon 12 volt conversion on my 1986 M1009 3 days ago. The conversion was relatively easy. The worst part involved finding the correct 8 gauge ring terminals and splices. I checked 22 stores before finding a forklift battery supply company that could special order them for me. They hooked me up well and then yesterday I found a Napa store 5 minutes from my house that I wasn't aware of and they had everything I needed, lol. Napa now gets all my business regardless if it's in stock or not.

I installed a high torque 12 volt gear reduction starter for a little extra power on cold mornings. If you do the conversion you are going to need a new rear starter bracket along with a new bolt set. The new bracket was for a 1989 Blazer. They went to the new gear reduction starter that year so any rear starter bracket for a 6.2 or a 6.5 liter from 1989 forward should fit the new 12 volt gear reduction starters. I also swapped out the 12 volt gauge because the 24 volt gauge flat lined after I did the conversion.

My overall opinion so far is good. My truck runs better without the second alternator. It has better acceleration and it should get better fuel economy as well. It also took care of the short that was in the wiring going either to or from my gen 1 light. In my opinion less components and lower voltage equals greater reliability. If I was a collector I would feel differently but my CUCV is my primary vehicle and the 24 volt system didn't meet my needs.

My next big project is to install an in dash aftermarket AC system. I'm going to mount the compressor where the gen 1 alternator used to be. That way it won't conflict the Banks turbo system that I'm going to put on later.

As far as cold starting is concerned the 24 volt starter has a slight advantage but nothing worth being concerned about. Ever since I replaced my injectors and my glow plugs my truck has been easy to start anyway, so no regrets on that front.

And lastly, I will speak to those who like to say, "No one will ever be able to help you when you have a problem", now you don't have to say that in post to me, lol.

The bottom line is if you save your parts you can always change back in a few hours. And it's not that hard to figure out a problem if you have one. By changing it over you actually simplify the system so as long as you understand it, it won't be a problem.

 

[FireFighterHill]

one of the HUGE advantages 24 volts has over 12 volts is AMPERAGE. Using 12 volts requires DOUBLE the amperage that 24volt does. With Double the amperage you need thicker wiring to handle it and with double the amperage comes much more heat because of the increased resistance. I understand your reasoning for wanting a 24 volt system, while it is less complicated, it is far from superior.

 

[hndrsonj]

Better acceleration and fuel economy by going to 12V? How do you figure that?

 

[Vhyle]

The only thing I can think of that MAY hinder acceleration and fuel economy, is two alternators operating on full load instead of just one. As we all know, an alternator providing full load doesn't spin as freely as one that isn't.

But even then, the difference is so marginal, I really don't see it affecting economy and acceleration that much. Especially in a diesel, which is obviously oriented for torque.

 

[hndrsonj]

I gotta call BS on that one....

 

[scottladdy]

Electrical System Voltages

Figure about 5-7 HP to run an alternator on full draw. While there is some loss spinning an alternator that is "off", it is marginal. Passenger side alt. in stock config charges the rear battery, which is only used for starting, unless you have 24 volt accessories installed. There should be very little parasitic loss with the second alternator, especially after the rear battery is charged.

If I'm not mistaken, GM uses dual alts. in their current 12V diesels. Given the push for fuel efficiency, why would they do this if it had a noticeable affect?

The "12v" alternator in either configuration runs the truck. That loss is the same regardless. Although I do believe it will take longer to re-charge the 12v only system with a single alt after a start cycle. Which if true would mean the alternator would have a high draw for a longer time period.

One more thing to consider regarding reliability. Increased voltage actually increases reliability of systems. Years ago all automotive electrical systems were 6 volts. As demands on the system increased the manufacturers changed to 12 volts for a number of good reasons, including increased reliability as poor connections would pose less of an issue with the higher voltage. For heavy duty systems (big rigs and the like) 24 volts is the standard. Now, with all of the electrical demands there is serious talk amongst the automotive engineering groups of increasing again to 42 volts. http://www.vishay.com/docs/72795/72795.pdf

Like the others said, I am challenged to understand a seat of the pants noticeable difference.

Regardless, I am very glad you are satisfied with the conversion. Thank you for posting your experience and keeping another old beauty on the road and out of the scrap yard.

Please post your mileage figures and let us know if you see any difference in MPG. A dyno run would be appreciated as well .

Best regards ...

 

[porkysplace]

I gotta call BS on that one....

 

[doghead]

The gain will be lost when he adds A/C.


Most of the OP's post is written as opinion, nothing wrong with that.

The comments about power and mileage are debatable. But no point in derailing his thread for sharing his opinion.

 

[Cucvnut]

I though AC was going 70 mph with the windows down and kick panel vents open?

 

[steelandcanvas]

Any increase in acceleration or fuel economy would be negligible at best. If it works for you, that's what counts.

 

[twomorestrokes]

Any increase in acceleration or fuel economy would be negligible at best. If it works for you, that's what counts.

Very true. Personally when I get ready for a race I just temporarily loosen the 2nd belt. That being said, I don't have an issue with someone wanting to do the conversion. Or ANY conversion for that matter. I think the 24v system is cool and unique but some others think differently. Sometimes when adding accessories it is easier to drop the second system.

 

[doghead]

You have raced your cucv, and actually loosened a belt prior?

Suprised you would go though such effort, and also suprised you didn't loose it all together.

What kind of race?

Come on now...

 

[porkysplace]

Maybe he Dyno'ed it with 24v and with 12v, thats the only way to prove theories on performance improvement.

 

[twomorestrokes]

You have raced your cucv, and actually loosened a belt prior?

Suprised you would go though such effort, and also suprised you didn't loose it all together.

What kind of race?

Come on now...

 

[Recovry4x4]

I have no problem with deleting the 24V side of things at all. Each person has their own ideas of what works best for them. For anyone who wants to convert, delete, add or subtract anything, you don't need to justify why you are doing it at all. Your truck, just do as you wish. I think most of the ribbing, jokes and hurt feelings comes from folks wanting the debate the reason or the justification put forth by the original poster. If you ask for opinions then be prepared with the flame shields.

 

[Mainsail]

Doghead starter relay conversion - a must
Everything else - opinions

At least that's the impression I've gotten reading these forums. I did the starter relay mod, but the glow plug thing and the 12V conversion advantages seem dubious. Sine mine is working great I see little reason to change what chevy has done.

My commute has recently gone from six miles each way, to 40. Every morning after the wait light goes out I crank it and it starts right up. I don't think I want to mess with that.

 

[Warthog]

I was going to say maintenance is a must but really it is also optional.

To the OP, thanks for sharing your conversion. The Rosscommon method is a good one that is well documented. The conversions that are not documented are the ones where getting help with an issue is a problem. A lot of guessing happens.

As a side note there are some mistakes in the Roscommon instructions. I'll have to find them tomorrow.

 

[hndrsonj]

For those who haven't visited the Roscommon site; they do have some very interesting and well thought out ideas.


http://www.roscommonequipmentcenter.com/

 

[dstang97]

1 question. How do you jump start other military stuff now?

 

[FireFighterHill]

1 question. How do you jump start other military stuff now?

You dont. You no longer have 24 volts.