Hey everyone,
I have a 1968 Ford F-100 with a 360, Auto. My voltage regulator went out on me Sunday. I replaced it this morning and my "ALT" idiot light in the instrument cluster is always lit. When I just turn the key to "Run" it is lit as well as after the vehicle is started. With my "old" regulator it never came on once....EVER! The "old" regulator is a Motorcraft thin style. I went to NPD this morning and grabbed the same one and installed it in the parking lot. I went home and checked to make sure the battery was charging with the alternator and it was. I checked this with a gauge on my battery charger. It's not an "el cheapo" charger. It says the alt was charging "high" but my battery is fully charged and new this year. Wiring is unmolested and all grounds are great as well as a great set of battery wires as well. I'm going to pick up a voltmeter today and check the voltage. Everything was working great before the regulator went south. I have a spare alternator I could swap after work today. Any ideas? Thanks.

 

If the light is burning dimly it could be a diode in the alt. If bright and the alt is charging points to the regulator. Did you hook up the ground to the regulator?

 

It is burning brightly....There is a wire coming from the alternator/solenoid loom and the radio..umm...the name escapes me. These are both connected.

 

I read somewhere that you should bolt the regulator to the core support before plugging it in. Sounds a liltte goofy to me. I've hooked them up before without any issues. I'm going to go over all my connections. I should mention this....it shouldn't make a differnece....but...Sunday the truck wouldn't turn over...so I put my battery charger on and started the truck. I checked to make sure the truck was charging itself by flipping a switch on my battery charger it will tell me what condition of charge I am getting(low/ok/high). It wasn't so I went in my garage and pulled another alt. I decided I'd check the regulator first....since it is a little easier. All I had though was a mechanical regulator. I bolted it up and connected everything and started the truck. I checked for charging and I was in great shape. So, the regulator was bad. But from past experience if you don't have the right regulator you will have issues. So, I drove to the local auto parts store and bought a regulator...the thin style which is what was on it in the first place...well the same as the old one that went bad anyways. I put it on in the parking lot and as soon as I turned the key to on (engine not running) the alt light came on. I started the engine and the alt light stayed on the same way as the mechanical one that I had thrown on. So I figured the generic regulator I bought was junk or not the right one so I decided to drive back home and I'd hit NPD for a new correct regulator Monday morning. So here I am Monday..nearly lunchtime with the same issues. Except that it is overcharging and the alt light is on as well as $30-35 in the whole. I am not wantig to throw parts at the truck. I know the charging system on these trucks aren't difficult. I've been searching the forum for similar issues but no luck. I'm going to recheck and clean all my connections (battery/alt/solenoid/regulator/grounds) to absoultely make sure they are all good. Can anyone think of what else I could check?

 

In 1982, Ford replaced the original alternator regulator used on 1965 and later trucks: C3SZ10316A with E2PZ10316A - the "thin" electronic type with Motorcraft marked on the cover.

In 1990, Ford replaced E2PZ10316A with FOPZ10316A (Motorcraft GR540B).

MSRP: $50.93 / FTEpartsguy.com price: $27.50

 

Thats right NumberDummy (A.K.A. Bill)...The regulator that went bad has the E2PZ10316A number. Any clue as to why they were replaced? Are the original Autolite regulators bad?

I figured out my problem. I beleive. I cleaned the connections on the regulator as well as the battery and solenoid. No change. I then took off the alternator and proceeded to take off the connections off the back of the alternator. As I turned it over what do I see, the red wire that is all by itself in the rubber cap was broken off from the ring connector. I thought to myself, this has to be my problem. I am at work so I had to improvise. I found some wire and a ring connector and cleaned and recrimped a new connector onto the wire. Reassembled the harness...bolted the alternator back on as well as cleaned up the block/battery gnd and alternator gnd connections. Got it all tore down and back together in 10-15mins. Turned the key to the "ON" position....crossing fingers..."Alt" light lights up. I beleive it is supposed to do this, it just never has....EVER! Drove it for 7-8 months with it not doing this. Never an issue till last Sunday. So, I proceed to start the engine. WALLA!....no "ALT" light! I have yet to check to make sure I'm getting the right voltage and whatnot. By the way, maybe NummberDummy (Bill) can make a comment on this....is the harness for the Alt/regulator/solenoid the same on a '72 F-250 camper special and my '68 F-100? Thanks again.

By the way....I am right in saying that the "ALT" light is supposed to turn on when key is switched to "On" engine off...but go off as soon as engine is running correct?

 

you are correct.

In fact, in some charging systems, the ALT light is in the charge signal circuit. If you unplug the bulb, the alt won't charge! This being said, I'll bet if the bulb burns out, the alt won't charge (unless there is a bypass in the bulb)

 

Ok, went home and fixed the wire properly. Without anything on and truck not running I have 14.4-.5 volts at the battery on my handy dandy volt meter. Start the truck...I have 14.6 when supposedly charging. But, according to my battery charger I have 14 volts when not running and it is charging at 18 volts. Also, my "ALT" light isn't staying on after I start the truck. Everything seems good so far. I'll keep my fingers crossed. Thanks again

Thanks for the info RHETOR...I'll keep that in mind for future referance.

 

It has nothing to do with Auto-Lite, because the original regulator was used by both Auto-Lite and Motorcraft.

The only difference on the Motorcraft regulator is the decal on the cover and the color of the cover itself.

You are prolly wondering what the heck I'm talking about.

In 1972/73, Ford was forced by the US Gov't to sell Auto-Lite because the Gov't said Ford had a monopoly on auto parts.

So, in 1974, Ford started a new company = Motorcraft. Ford transfered all the Auto-Lite part numbers over to Motorcraft part numbers.

The 1963/73 regulator's cover went from blue to black, and now said Motorcraft on it.

Ford also changed the original part number from C3SZ10316A to D4TZ10316A (I didn't mention that earlier, because it wasn't relevant).

The D4TZ10316A Motorcraft regulator was replaced in 1982 by the electronic version = E2PZ10316A, that number was replaced in 1990 by FOPZ10316A.

 

Thanks again Bill. I appreciate the information and insight. I guess the mechanical regulators were not as good as the newer style because they corrode/burn up or stick....atleast from what I've read. Call me old fashioned but I like things like ignition points and whatnot. I envy the earlier generations. I'm just a young pup but I have an immense respect for...ahem...the wiser generation from a time when I wasn't around. Not calling anyone old by any means. As for the Auto-Lite info about Ford selling...I had just read that in another post that you had contributed to Bill. All this information is interesting to say the least. Thanks again Bill and everyone else for your input. I'll post again if my fix didn't hold.

 

18 volts is a lot to charge a car battery. Are you charging on "boost" or "engine start" mode?

It is best to let the battery sit for about 30 minutes with the engine off before you check the voltage. It will dwell around the alt output voltage for a while before eventually settling back down to 12.6V

The 14.6V charging current sounds good.

If the battery winds up being dead after the truck sits for 2 days, you may have a bad diode bridge in the alt. A good way to check for bad diodes is to set your multimeter to AC voltage and check for juice.

 

Sorry, I should have specified. I wasn't charging the battery when I got the reading of 18 volts. As for the "sit for 30 min". You are correct. It went down to around 12.5. If I start the truck with the charger hooked up but not charging the battery...I can flip a switch on the battery charger and it will tell me what the alternator is charging at. It climbs to 18 according to the gauge. But my volt meter says 14.6 volts give or take a point. Unfortuntely I don't let my truck sit for more than an evening. I can try this weekend to leave it sit and see where my battery sits. Can you elaborate on checking for a bad diode? My multimeter does measure AC. I'd like to check it myself...hate to have it checked at the local parts store. The machine just seems so rinky-dink to me. And besides, I like to learn new/helpful things to further my education. Thanks RHETOR

 

You should turn the stereo, blower, and wipers on in the truck to load the alt as much as possible.

Then switch your multimeter to AC and check the battery. A general rule of thumb is less than .5VAC and she's good.

The alternator outputs AC voltage which is then sent through a "conditioner" of sorts. The current is passed through diodes which limit the flow to go in one direction (positive and negative DC) The DC output is then sent to the voltage regulator, which modulates the strength of the electromagnet in the alternator to get the proper output voltage. This is rather interesting. If the regulator is sending "full field" or telling the alternator to put out as much as it can, it is actually harder to spin. The alt will freewheel if there is no current passing through the electromagnet, and can consume as much as 15hp when fully energized, depending on the output of the alt.

The AC test is a good way to identify a clearly failed diode. While this does mean that it will not catch all failures, it will tell you if something is very wrong. The AC test tells you if one of the diodes is letting AC voltage "escape."