[Megunticook]

Just finished plowing the road, as I was parking the truck I noticed my new handy-dandy voltmeter jump up to 16 and then it looked like it was higher (the needle was pegged at 16). I flipped on the lights, wipers, and blower motor, just out of curiosity, the needle dropped momentarily but then was up at 16 again.

The voltmeter's only been in there a few weeks, but it's been reading 13-14 generally, depending on how many accessories are on.

This is almost surely a voltage regulator malfunction, is it not? WTF--I just replaced it last spring (Standard Motor Products brand) after the last one went wacky (an AC Delco brand unit I had installed a couple years back.

I have an extra SMP one in the shed which I can swap in, but is there anything else I should be looking at? Could something be causing these things to fail prematurely? Seems kind of extreme. I could understand if these were $10.99 China-made specials from Checker Auto, but I've been using quality brands and paying $30 a piece for 'em.

Just the luck of the draw, or am I missing something?

 

[bherder]

Check your battery (engine running of course) with a VOM (Multimeter of known accuarcy) and see if it matches what your voltmeter is saying. Hey, even 'quality' parts can go buns-up prematurely...
I would also, if you haven't already, make sure you've got good solid connections between the field connections and the VR...

 

[DiverDwnPowrRam]

or look at your dash lights with engine idling at night...if they are pulsing..then you are probably right....VR.

 

[bherder]

or look at your dash lights with engine idling at night...if they are pulsing..then you are probably right....VR.

Actually, a pulsing (Like a strobe light effect) is a bad diode(s) in the alt.
If you're talking about lights going dim to bright from idle to anything above idle is pretty normal.
Diodes very rarely ever go bad (Which is why the cheaper rebuilds use them over and over) but they can. But I doubt that's Ed's prob...

I'm betting that either it's the VR gone bad, OR wiring. The VR besides having the duty of controlling the juice that runs through the field winding, which in turns controls the voltage output produced by the stator windings, it also needs a good feed from the rest of the system to know where it's at.
The VR, when the engine is first started (Ignition turned 'on'), gets 12 volts through it so as to 'excite' the field winding. After it's running, it gets it's feed from this same wire, so it can sense what the system voltage is and 'adjust' the juice to the field windings.
If this wire, is damaged/old/corroded/crappy connection ... Something that is introducing more resistance (and therefore a voltage drop) into what the VR is 'seeing' it could cause the VR to produce more voltage than necessary. This probably is not the case, but it IS a possibility..

 

[DiverDwnPowrRam]

maybe...but i have found in my testing of bad VR and maybe it is coincidence.... if you are at idle, such as waiting for a long light at night and you notice that your head unit and your instr panel is doing a slow pulse dim normal dim normal closely matching Hz...the VR was to blame. Replacing this seemed to not only stop the pulsing but the battery would then charge normally.

 

[DODGEN1]

make sure that the terminal are tight. crimp them tight. loose connectons will make it pulse or show high charge.

 

[Speed Dragon]

Actually, a pulsing (Like a strobe light effect) is a bad diode(s) in the alt.
If you're talking about lights going dim to bright from idle to anything above idle is pretty normal.
Diodes very rarely ever go bad (Which is why the cheaper rebuilds use them over and over) but they can. But I doubt that's Ed's prob...

My Dippy has that problem, fast pulsation of the lights at any engine speed. I swapped the VR and no change, so I assumed it was a diode in the alternator. Nice to know I guessed right

Megunti, in the VR grounded good to the body? Where is it mounted? I've heard the bad grounding can cause problems.

 

[bherder]

maybe...but i have found in my testing of bad VR and maybe it is coincidence.... if you are at idle, such as waiting for a long light at night and you notice that your head unit and your instr panel is doing a slow pulse dim normal dim normal closely matching Hz...the VR was to blame. Replacing this seemed to not only stop the pulsing but the battery would then charge normally.

Ah, well, thats why I was wondering what you definition of 'pulse' was ....
I'm talking a really rapid pulse... Like a strobe light. Yeah reaaal slow is likely the VR....

 

[Megunticook]

Megunti, in the VR grounded good to the body? Where is it mounted? I've heard the bad grounding can cause problems.

When I redid my whole charging circuit from A to Z a couple years ago, I wire brushed the firewall around the VR mounting holes to clean shiny metal and also used new stainless mounting hardware. In addition, I installed a new heavy braided strap between the lower mounting screw and the block. With all that it should be well-grounded. I suppose I could run a jumper wire from the neg. battery post to the VR just to check, but I'd be very surprised if that's the issue.

I also replaced the connector that plugs into the VR--but I suppose there could be an issue there--I'll look closely at it.

Seems weird to have a couple VRs go bad in 3 years time.

 

[DiverDwnPowrRam]

Well Bruce and Speed could be right but until i found the common denominator (Made in China) I did see two VRs go bad within 6 months. So anything is possible Mcook....

 

[Megunticook]

The last 2 VRs have been AC Delco and Standard Motor Products--both stamped with "Made in USA" and both about $30.

Sad to say, I ordered a spare SMP one last spring, which is the one I have in my parts box now, and I was disappointed to see that they're now made in China.

Maybe I should go back to AC Delco--although that one went south on me after about a year.

Be curious if the original Mopar VRs that came with these trucks when they were new were that flaky...

 

[Speed Dragon]

My '72 has a '71 VR in it...

 

[bherder]

Ya know Ed, sometimes I think it's just the 'luck of the draw' ...

As Diver sez that he's seen 2 go bad in 6 months (And I'm SURE 'MIC' has a LOT to do with it..) sometimes even a 'quality' ... Or what we think nowdays is quality... part goes bad. Especially electrical stuff.

On the other hand ... when I first bought my truck ... Mmmm 7-8 years ago, when I first got it, I was driving into Spokane one day. It was after the amp gauge was disconneted (PO) and before I installed a volt gauge. I'd basically had this rig for a month or less.
I stopped in a parking lot, shut the engine off and when I got out of the truck could hear something boiling. It was the battery.
Well, there happened to be an Autozone in the lot I parked in and one of the countermen was kind enough to bring out a VOM and check the system. Sure enough, 18 volts constant when the engine was running. Being as it had a near-new Interstate battery in it, I sure as shit didn't want to cook it, so I bought the cheapest VR they had.. Like $15.00 ... I just wanted to get it home.
I have no idea, because I didn't think to look as to where it was made, didn't care at the time, but it was, and still does, put out a perfect 13.8 volts (I've got a 'Made in USA' Standard Ign one sitting on the shelf, because I was SURE I was going to need it pronto) ... But my crappy 'Made in Who-knows-where' one has worked flawlessly for 7-8 years...

So, like I say... sometimes ya get lucky, sometimes ya get shit on again and again... Luck of the draw... :dunno:

 

[Megunticook]

Well, I grabbed my tach. and multimeter, fired it up, and the meter read a steady 14.6 V at 1250 rpm (I was checking against the FSM specs). The gauge in the cab read similarly, although it seemed like I saw the needle twitching a bit. Wonder if that gauge is screwy? Or maybe this is one of those dang intermittent problems. I'll keep a close eye on things for now, maybe toss the spare VR in the glove box just in case...

 

[Megunticook]

Well, we had another storm last night (good 16 inches or so), so I went out to plow and within 5 minutes the voltmeter was pegged whenever the motor was running above idle. I heard the blower motor speed up, too, so I think the meter is accurate. The ammeter reader showed the battery was being charged when this happened.

So I put the new VR in, but I noticed in the directions that come with it, they suggest testing each of the wires that plug into the VR for a short to ground. I did this and found that the needle did move when I tested each of them, using one of the valve covers as a ground. It read about 3 ohms resistance (I made sure my meter was calibrated so if you touch the leads together you get 0).

Is this telling me something's wrong? Or would that be normal? Is there a path to ground through the field terminals?

I rewired the whole charging circuit a couple years ago, using new wire, terminals, etc., so the likelihood of there being a short to ground seems small. But I will check every inch of every wire if necessary.

With the new VR, the voltmeter stayed at about 14.5 at all times. However, as I was getting ready to shut down, and turned off the lights and blower motor, the needle started dancing around crazily and read way low, when I turned the lights back on it returned to normal and stayed there even when I turned the lights off again.

I'm suspicious that something in my charging circuit may be damaging the VR over time, but I'm not sure and don't know exactly how to pinpoint the problem, if there is one.

 

[DiverDwnPowrRam]

if it is dancing like that then maybe speed and herder are right and your one way gates..diodes.... may be bad.

 

[Megunticook]

if it is dancing like that then maybe speed and herder are right and your one way gates..diodes.... may be bad.

Is there a test you can do to confirm that? (I don't see where Speed and Herd said anything about bad diodes).

Another clue--I drove to town yesterday to fill up the tank, and it seemed like the needle bounced whenever I hit a bump. It never went above 14.5, but it would drop to 12 and even well below that at times. When the truck was stopped, it seemed to stay put at 14.5.

This would seem to suggest something is loose. I'm wondering if maybe the screws holding one or both of the male spade terminals on the alternator field terminals is loose...I don't really see anywhere else in the circuit where things could be loose (again, I rewired everything a couple years ago with new wire and terminals, crimped/soldered/shrink-tubed all splices and terminals). I checked the female terminals on the wires that plug into the VR, they were tight.

Anything else I'm not thinking of? You suppose this issue is blowing out my Voltage Regulators? As I say, I put a new one in when I rewired the charging circuit 2 years ago, then when that started acting funky (ammeter was sporadically reading "D" when driving), I replaced it last April, and now a third one.

 

[fins2fuselage]

M-cook,

Could the ground from your body to your engine be intermittently bad?

A 10 ga. wire should run from your negative battery terminal to your left front fender, grounding the engine to the body via the larger battery ground cable.

Also, you should have a ground wire or a braided strap running from regulator mounting screw to a bolt near the back of the engine (manifold or valve cover, I think). If it is present, check for good contact. I can't believe that they located it to the regulator mounting point arbitrarily; I think that the location must be a substantial part of the design. In my limited experience, bad grounds account for about half of the electrical problems encountered in our Dodge trucks.

Bherder, please comment if I have given M-cook any incorrect or non-pertinent info.

Jeff

 

[bherder]

It all sounds good to me Jeff...

One of the first things I did when I got my truck was to check/replace ground wires. And yes, from the factory, there is a ground wire from the battery to the Rad mount (I replaced mine with 10 gauge wire) and a braided strap from the VR mounting bolt to one of the coil bracket bolts on the intake manifold. (I replaced that with 6 gauge wire)...
I'm gonna guess though, knowing how 'overly cautious' Ed is about these things, he's probably already cleaned/replaced these..

Ed, to test the diodes, you have to completely dissassemble the alt... Of course this isn't a 10 minute job... However, the diodes are in the stator winding circuit, which is electrically isolated/seperate (At least when the alt is sitting on the bench) from the field windings, which gets it's juice from the VR...
I'm assuming you replaced/rebuilt the alt, from when you had a loose/wiggly battery connection on it? and I'm sure you've already been over all the alt/VR connections, like 8 times, now?
I would check the voltage from the system that feeds the VR/field windings ...
If you have no juice going to the field windings to 'excite' the rotor, all it is, is dead weight spinning around...

 

[Megunticook]

A 10 ga. wire should run from your negative battery terminal to your left front fender, grounding the engine to the body via the larger battery ground cable.

Mine runs to the radiator support, but yes, I replaced this with new wire/terminals/mounting hardware a couple years ago and keep a pretty good eye on it. It's clean and tight.

Also, you should have a ground wire or a braided strap running from regulator mounting screw to a bolt near the back of the engine (manifold or valve cover, I think). If it is present, check for good contact. I can't believe that they located it to the regulator mounting point arbitrarily; I think that the location must be a substantial part of the design.

This was missing when I bought the truck, and I ran it that way for years out of ignorance. A couple years ago, however, I installed a beefy braided metal strap and connected it from the lower VR mounting bolt to one of the coil bracket mounting bolts, so the VR should have excellent continuity with the engine block. I also replaced the ground wire from the alternator body to the block. So I should be well-covered as far as grounds. But I will double check all of these again for looseness.

In my limited experience, bad grounds account for about half of the electrical problems encountered in our Dodge trucks.

Agreed...probably three-fourths of the problems.

I checked those screws mounting the field lead clips onto the alternator--they seemed plenty tight.

What about that result I got when I tested the terminals of the two wire leads in the VR plug for continuity to ground? The Standard Motor Products instruction sheet that came with the VR said to always test for a short to ground on both of these wires before installing a new regulator. The needle on my meter moved to about 3 ohms on both of those wires when I touched one test lead to the valve cover. Does this qualify as a short?

If anybody had a second to do a resistance test on those 2 wires on their truck, I'd be curious about the results.