94 12v swapped into 2002 24v charging issues

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Tj419

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Nov 12, 2013
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My 24v puked a wrist pin thru the #6 piston so I decided to put a 12v in its place that I had on the stand for another project. Got the 12v in and running but it will not hold charge at all the tach doesn't work and the temp gauge flys over to 240 soon as the truck is started. Any help on this is appreciated thanks
 
It won't charge until Vcm sees a tach signal... Get a 98 12v engine harness and vcm
 
I have a destroked tach kit hooked up just for it to get a signal and still nothing
 
Just put a ford voltage regulator on it then worry about the tach kit just to run the tach


Sent from my flashscan v2
 
Tj419 said:
Just a ford 12 volt regulator?
Click to expand...

Vr440 from NAPA, they also sell a mating plug part #VRC428



This will eliminate the PCM from the charging system entirely.

There are 4 terminals on the regulator total.

I - is not used, it's the "separate" terminal

A-goes to the +battery cable on the alternator (Large post), put a ring terminal on the wire you use, this is the voltage sensing wire

S-goes to the ignition switch or wire that's hot when the key is on, this is the "turn on lead"

F- goes to one of the smaller post on the alternator, if you're using a 12 valve alternator. If you're using a 24v alternator with the plastic 2 pin plug, cut the wires back a few inches from the alternator. Wire one of the 2 wires to the F terminal.


The other wire from the plastic field connector needs to be grounded.

Costs about $45, enjoy the reliable charging.

Will
 
Also, you'll need to adapt to the 2 pin 24v style temp sensor where the 12v one (at the back of the head) is just a single wire.
 
Thanks for the info got it all wired up and it's working good so far
 
You basically need to make the truck think the 12V is an '02 24V.

You'll need 24V sensors and the 24V ECM. I believe the '02 24V gets it's tach signal from the cam sensor.

What tranny are you running? If an auto, you'll probably need to run the 24V APPS.
 
I'm adapting my sensors to the 12v with pipe thread fittings and I'm using the nv5600
 
And bigpapa yes the 02 gets its charging signal from the cam sensor 01 is the same way
 
You can take a day to swap the cam out and modify the front cover and put your cam sensor in there.
 
will24 said:
Just put a ford voltage regulator on it then worry about the tach kit just to run the tach


Sent from my flashscan v2
Click to expand...

I did this with my truck because my ecm wasn't working to charge the truck.

A little while later I ordered a transpo vr8315 voltage regulator which does the same thing as the external voltage regulator but the transpo is a much smaller unit and able to hook right onto the alternator giving it a much cleaner look.
 
Easy swap if homework is done. And questions are ask before hand. Cam is alot easier to pull wen motor is out on the shop floor, not in the truck. I've made several sets of all the adapters that are needed to convert your sensors. After I done my swap for other guys doing the same thing. And 98 12v harness and ecm will not work in 99 up truck as body harnesses are totally diff.
 
Yeah the true 98 12valve harness works fine in a 99-02 truck. It does need the 98 PCM as well.
 
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