Technical 6 to 12 Volt Conversion Problem

Working on a 1950 Ford 2 door Custom with a 1953 flathead V8 engine and automatic transmission installed in it. It has also been converted from 6 volt generator to 12 volt alternator ( conversion kit unknown and wired by others). The car has run fine for 8 plus months, but recently the battery was going dead. Discovered the alternator (1 wire) was bad(tested at local O'Reilly Auto Parts and failed test). Upon installing a new(not remanf) alternator ( which local O'Reilly Auto Parts tested and it p***ed ) will not charge the battery when installed on the vehicle. Tried applying voltage to the relay terminal on the alternator and still only shows battery voltage vs expected 14 plus volts with engine running. Anyone have any experience with 6 to 12 volt conversions and run into this problem?

 

Are you sure they sold you a one wire alt?

 

Yes sometimes a one wire needs to be excited from usually the ign power supply..

 

what do you mean by "applying voltage on the relay terminal on the alternator " ?

 

If it is a 1 wire they often don't kick in until you rev the engine.

 

The problem is that you are trying to run a Chevy Alternator on a Ford engine. The remedy is to chunk the Ford and install a mouse motor. It's a traditional swap and you'll be able to drive the car, instead of having it sit in the driveway

 

Brilliant, just brilliant!

 

Now you know why I don't like 1 wire alternators. I'd insert the quotes if I knew how, but some sold as 1 wires have the other two terminals, and need a shorting plug. Either that, or using the idiot light to excite them. I've had them that had to go as high as 3000 rpm to self excite and start to charge. They went blind, of course.

 

http://www.oldengine.org/unfaq/10si.htm, http://www.oldengine.org/unfaq/six12.htm

 

post some pics - where is batt/ what gauge primary wires to batt & starter/relay?

 

I have a locally rebuilt single wire '78 GM alternator on my Ford and and it's been working fine for 18 yrs! Also it charges at idle from the git-go without reving. I know some have to be reved to about 1500 RPM to get them to charge.

 

I was just joking around.

 

The first time you start some one wire alternators you have to apply 12 v to either of the two stud terminals for it to work. New alts have no residual magnetism to start charging. From then on it should be able to charge with a little Rev of the engine.

 

Thanks for all the great replies! Will check them out and post the results.

 

It is so ******** simple to wire a Delco 10 or 12 SI alternator so it works right that I can't see why anyone would waste their time or money on a "1 wire alternator" The 1 wire setups were originally for conversions on farm equipment and diesel rigs before the hot rod guys picked up on them because the one wire setup cleaned up clutter on the engine which was the original hot rodder reason for using them.
If your new to you 1 wire alternator didn't come with the cover or cap over the two pins as you see in this shot it wasn't a true 1 wire alternator.


Two different but easy wiring diagrams to hook up a regular delco 10 or 12 Si alternator on most any rig.

 

You can also wire in the diode as shown above to excite a one wire alternator,many one wire alternators are higher amp and require a larger gauge wire than 10 gauge here is a chart: http://www.tuffstuffperformance.com/files/pdf/1-wire_alternator_instructions.pdf I run a 6 gauge to battery positive with my 100 amp unit,4 years no issues.

 

Thanks to all those who posted intelligent suggestions/links with regards to the alternator not charging.
The alternator did turn out to be a 3 wire vs a 1 wire.
Seeing as this application does not have an idiot light, all we did was run a wire from the start solenoid to the #2 field terminal on the alternator which supplied the needed voltage to make the alternator charge.... which it now does.
Thanks for the diagrams from those who sent them. They were most helpful. Thanks also to Gary B. for all the help getting this done.