The Stovebolt Site Forums The Shop Area The Electrical Bay 6 volt conversion questions

Hi. Finally, after years of driving my "Miss Daisy" and erratic winter starts I decided to convert the 6 volt electrics to 12 volts. So I thought I'd compile my questions into this one post and appreciate your suggestions :

I've rounded up an '80's Delco 10si alternator. What is a 'DA plug' and do I need it on this alternator?

I have several 12 volt coils laying around (different manufacturers) but don't know if any are 'internal resistor' types. How to check?

Previously installed a large capacitor to the fuel guage to correct for hysteresis and it works well. Do you think it will also mitigate any full-time 12 volt damage to the guage? -- 12 v jump starting doesn't seem to harm the guage.

With the battery under the pass side floor, what battery group size is the current 6 volt system and what is the equivalent 12 volt battery BCI group sizing?

Need a list of equivalent 12 volt bulbs for direct replacements.

Even though this truck is a Chevy 3100, I've now found a GMC the heater/blower and it bolts right in. I believe GMC is normally positive ground. Will the power leads need to be reversed with this Chevy negative ground app?

For voltage reduction on the guages, etc., can appropriate zener diodes be used with any success?

bet most of these questions can be answered by a good search, tons of stuff about the conversion here on the bolt.............

I would leave it as is but.......nothing wrong with a six volt system as long as it is in good working order.............

I agree with joker about 6v, unless you want 12v accessories. Too small a battery cable gauge is primary culprit for hard starting (12v cables are not adequate for 6v).

Nonethess, maybe this Tip in the Tech-Tip section will be of assistance?

I get what you are saying about keeping stock, but that's not my discussion.

So yeah -- erradic winter starts, overpriced batteries, dim headlights, insufficient charging from short trips, dangerous 12 v jump starts, slow windshield wiper motor, tired heater blower, hard to find bulbs, can't use newer radio, blah blah. After years of putting up with these they've become reasons enough for me to switch. It's not like everything can't be easily reversed at some point.

All I'm asking for is info that you may have at your fingertips and that will help save me from further ploughing through various threads and websites. Either folks want to share the info I'm asking for or not.

Perhaps I should post these queries one at a time?

The standard 6v battery is group 1. 12v sizes are also shown.

6v and 12v bulbs

Most vendors sell fuel-gauge resistors (Runtz style). Some people say that this reducer is not Runtz-style but it has worked fine for me. Your resistor/capacitor might work or might not - do you have a breand and part number?

You have probably seen this article on the 10SI

Here is another article on the 10SI

Check the resistance of the coil primary (the small terminals). There shouuld be a measurably lower resistance on the coils without the built-in resistor. I'm prejudiced against internal-resistor coils- - - -they can result in a hard start situation because of limited primary current under some conditions. Wiring up a ballast resistor and a bypass circuit isn't brain surgery, and untold millions of point-type GM vehicles used that system for a long time. If it wasn't necessary, would GM have spent the time and money to equip all their cars and trucks with the system?

The 10SI alternator only needs one wire connected from the main battery terminal to the regulator to begin charging properly if you've got the right regulator installed in it. There are lots of threads that detail the process. The second terminal on the regulator is only necessary if you choose to run the idiot light instead of or in addition to an ammeter.

Install a gas tank sending unit from a 12-volt truck. Problem solved!

The only voltage-sensitive dash gasuge is the gas gauge. The ammeter might need a shunt to prevent it from pegging right after startup if you've got a low battery, but it's not voltage-sensitive. It measures current, not voltage.

If you need a specific voltage supply to something (can't imagine what) use a potentiometer with enough current-carrying capacity to run the accessory, and use the variable-output wiper to dial in whatever voltage you need with the item in operation. Then lock the shaft down to prevent it from drifting off the setting.

There are plenty of 12-volt aftermarket heater blower motors that should fit your application in case you can't get the GMC unit to turn the right direction.
Jerry

Was the earlier sender 30 ohms and the later senders 90 ohms?

When did the 12v senders change from 30 ohms to 90 ohms?

Is this information correct?

Tim - yes that info is correct, the senders were 30 ohms, 6V or 12V until mid 60's, the 'voltage sensitivity' is in the gauge, not the sender

Bill

Wouldn't a 90 ohm 12v gauge give wrong readings? So, it would be best to use a pre-64 GM sender (and a voltage reducer) with a 6v gauge?

yes, mix n match won't work, have to use a 30 ohm sender with a pre-64 gauge, a 90 ohm sender with the post-64 gauge

and yes I'd say it'd be best to keep the original sender, with the original 6V gauge on a proper reducer .... no idea what a capacitor would do

Bill

Thanks for that information, fellas!

It all really helps manage my time in looking for it all.

To address a few comments --

tclederman : a great set of weblinks.
I see that group 1 refers to 6 volt sizing only.

I did find that BCI group 25 is almost a perfect 12 volt equivalent fit for the stock compartment under the floorboards (group 26 is close too).

Hotrod Lincoln : installing a 12 v gas guage instead is kinda out of the question for cost as I can toggle down the voltage with some sort of reducer. I think the potentiometer is a good idea and there are several in my shop.

As for the windshield wiper and motor, it was purchased some years back "as a 6/12 volt unit". It runs so slowly methinks it is really a 12 volter anyway. So, before I play with voltage reduction, I'm gonna try it on 12 volts.

As for the heater blower. Good point -- perhaps I can find something locally that will replace the 6 volt motor. Otherwise, your resistive method might be the ticket.



About the gas guage --

as mentioned above, I found that mine was originally hard to read properly. The guage needle would constantly move whenever the gas sloshed in the tank.
I thought this was normal for the vintage, so I put a humungous capacitor in line with it and it seemed to solve the problem (hysteresis?) ..it dampened the movement. It also seemed to provide some protection from 12 volt jump starts too -- didn't fry the guage.

I have recently read that the dial's over-reactive movement may not be normal afterall as even those early guages were built in such a way as to mitigate the problem (using a bimetal construct).

If so, can these guages be easily repaired to reactivate their native feature?
I can then turf the capacitor and just place a voltage reducer in line with it instead.