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1983 F-700 Voltage Regulator Questions


Micro Machine Manager
Hi all-

I just spent a great 11 hours broken down in the F-700 but avoided tow. Was going to my friend's place to install new 90a Alternator on the truck and pulled into Fast Trac to get gas. Well, it didn't start up after I filled up the tank. Niiiiice.

Friend came to me, we pulled the F-700 to Runnings Parking Lot but he managed to jump it while I was towing the F-700 with his plow truck. So that worked, but battery was dead.

Anyway, we actually pulled out the old OEM alternator and installed an enhanced larger 90a by Wilson Alternators. Added new hardware with neverseize and we were gonna change the belt except another belt would have to come off first, so the original belt stayed but we got it even a little more taught than original and looked to be in serviceable condition and no oil or cracks on it, frays, etc.

Meanwhile, battery was charging too and once the alternator was installed (about 9:00 pm that night) we were able to turn on the truck and all its low power symptoms went away (flashers and directionals were not working prior if I turned on headlights, etc -- now I know what a low power indication looks like, it's been a minute).

However, rather than heading home right away I sipped a coffee and then tried to take off. The darn thing died at the stop light at 10 pm once I got out of the gas station parking lot I had idled in. Darnit.

I got a rope tow from a really nice gent and a police officer pulled out to make sure nobody tried to hit us as we crossed the intersection and got myself safely parked in Walmart's no-overnights-allowed parking. ^_^

I was pretty sure I had ordered a starter (installed), alternator (60a Remy backup behind the bench seat) and a voltage regulator. I found it, brand new. Realized this might be the other problem. Well, I looked in the hood and yep the voltage regulator was old looking. Unsure if it's OEM or not, but I found something peculiar as I examined it.

The new VR has IASF (Ignition, alt/bat, stator, f-whatever) but the alt/bat was cut off. Now, that sounds like a good way to eliminate the alternator. HOW/WHY that is possibly cut off is beyond me. I've heard of eliminating the Stator per Google Research, or maybe the I-gnition? But the alt/bat?!?

On the bat connection of both old and new alternator installed I had two thick eyelets and on the Stator and F-whatever I had one each. I am 99% positive the S and F were wired correctly as I took a picture pre-removal and figured out on the old alternator which was the S and the F, plus when I looked at the old voltage regulator I found the orange/green did go to the F and the Red small wire did go to the S.

Is there any feasible way this VR that's installed can be working with the A not connected? And I looked for dangling wires and only can find the A-wire hanging off the Voltage Regulator and then abruptly ending just like several of my rides in the F-700 lately.

I wish I had taken a picture of the VR but did not. I do have a brand new one that I'm keen to install now after I do a few checks on the current VR (found a good test light and multimeter guide on YouTube for older Fords with VRs on how to test these things out). New VR is a good T-Series Standard Motor Products and has that new car look to it.

I'm considering rebuilding all the wiring. The positive/negatives are getting rebuilt already but the S and F look suspect. The I-wire might need help. I haven't scrutinized the I-wire, and well, then there's the A mystery that is culled about 3 inches beyond the A-pin off the Voltage Regulator.

TLDR: Voltage Regulator has A-snipped, how the hell is this a good idea? Should I just bypass and put it directly onto the starter solenoid? Alternator is not providing the 13.93 volts expected -- was about 12.4 when running (and dropping it appears).




Micro Machine Manager
This story was a lot crazier but I was exhausted. It definitely was a bit of an "Adventures with Bill" moment from The Red Green Show.

Highlight though:

Kieth was my friend showing up in his rebuilt Chevy plow truck.

The funny thing was he came to rescue/help my F-700 and pulled up behind me at the other gas pump, stall/parked and was immediately on fire under his hood. His power steering pump hose disconnected and shot gear fluid all over the carbureted engine and its AC control wiring caught on fire. It was insane. His brakes also broke (front lines) at that moment. I cannot make this stuff up. We put the fire out luckily not catching fire or anything literally at a gas pump. I guess it would have ended my problem though as a total loss of f-700 at gas station fire would probably have been a good payout and shorter day. All the same, glad I didn't have that experience.
The old regulator might not have had the guts it needed to handle the new, 90A alternator. You know, more current out requires more field current in. The higher field current may have caused the old reg's relay contacts to pit and quit. OR, if you were charging the battery while you changed the alternator, the old reg and the 90A alternator may not have ever worked together. The little bit of energy restored by the quick charge might have fooled you the same way some people are fooled after they go out and buy a new battery when the alternator is the problem. A month or so later, they're stuck on the side of the road because the new battery fooled them. Yes, I've seen that happen. It CAN take that long for a new battery to go down.

The removal of the A terminal of the new regulator is another story, though. I'm not sure how advanced Ford automotive electronics were in 1983 (or 1982, the year they actually built your truck), but I think they might have begun to integrate more functions into what has been called " the brain" of the vehicle along about that time. Maybe, just maybe, they experimented with moving the voltage level sensing function to the brain (now called the Power Train Control Module) or to some other module like the ECM and having it regulate the alternator output by varying the voltage applied to the field coils or the current through them. I don't think they'd try switching it on and off (varying its duty cycle), because inductive kickback off both the field and stator coils might damage some of the other modern electronic components. In fact, if the new reg is potted, it may not even have a field coil relay anymore, but, instead, a MOSFET or IGFET that could be turned on and off gradually in the enhancement mode to reduce inductive kickback from the alternator coils.

If that is what they did, the A terminal is no longer needed. It was only there to supply battery voltage to the field coil relay, anyway. The output current from the alternator on its A terminal was not controlled directly, but, instead, goes straight to the battery. It WAS controlled by the round about method of using the field current relay to switch the field current from full on to some fraction, usually around 4/5 to 5/6 of maximum, to full off. FETs have gates that take almost negligible current, as opposed to the much greater current of an activated relay coil. This near-negligible current can easily be supplied from the Power Train Control Module or the ignition switch wire, the REGULATOR's S terminal.

If the new reg and the new alternator are the correct ones for your truck, they should match any new developments in the rest of the electronics. I say, "Give it a try, as is. See if it works."

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