voltage spike?

[Jim100]

1970 w-100 with electronic ignition. Flat voltage regulator.
I was driving and I happened to hear the fan blower noticeably speed up. I glanced at a digital volt meter I have on dash and saw it jump from 14.4 to 17 for about one second. A few minutes later it did it again for a second. And then not again for the rest of my hour long trip and I have not noticed it again having driven in a couple days later for an hour.
Is this just an anomaly or a sign that something is failing? Do I worry too much?
Thanks,
jim

[stumblinhorse]

I would say that you have something failing. Probably VR. I didn't know as much about this until I had Alt and VR problems and went through a few of each to get my stuff working. There are really only a couple of component in the whole system in these older trucks. Since you have a digital gauge you are way ahead of the crowd. Just keep an eye on it. But you might want to try to source a VR and have it on the ready if it totally goes and starts to overcharges your battery...

Edit: And don't assume the VR you get is working...I went through 3 out of the box, new and NOS, before I got one that works. But it is nothing like the stock one and the truck needed modification to mount it.

[dodgeboykim]

Wouldn't hurt to go through all grounds and connections.

[Jim100]

New DELCO voltage regulator. Carefully grounded. My aftermarket voltage gauge shows 15 at idle and then goes up to 18 plus with higher RPM.
Hooked multi meter and tested voltage across batter at idle and under high rev and same as dash gauge. In fact meter showed 19.
This is driving me crazy.
The ohm test on the regulator is 1.85 and not 1.75 like the guy on u-tube suggests. Is this difference enough to cause such high charging volts?
jim

[stumblinhorse]

I would guess your new VR is faulty. The system is pretty simple, the VR limits the amount of volts that are sent to the field on the alternator. The more sent the higher the charge. Your new VR is sending too much to the alternator. The original VRs allowed for some adjustment up or down in charge. Does your new one allow for adjustments?

[Jim100]

No adjustment on the delco. I have found a HD adjustable on ebay I will try. Going to clean up some suspect looking wires too. Thanks,
jim

[PwrWgnDrvr]

That is not how the 1970 VR works and it is NOT adjustable.

1970 is an isolated field alternator and the VR is in the circuit between the alt field and ground. The VR is an electronic unit that varies the resistance to ground, thus limiting current flow thru the field. Are you using an OEM VR or some aftermarket gizmo?

If you are using a std VR for a non isolated field system, its not going to work. They are not interchangeable. Most vehicles used the std system in those days and most regulators are for that type.

[stumblinhorse]

That is not how the 1970 VR works and it is NOT adjustable.

1970 is an isolated field alternator and the VR is in the circuit between the alt field and ground. The VR is an electronic unit that varies the resistance to ground, thus limiting current flow thru the field. Are you using an OEM VR or some aftermarket gizmo?

If you are using a std VR for a non isolated field system, its not going to work. They are not interchangeable. Most vehicles used the std system in those days and most regulators are for that type.

You are always very confident of this stuff, but the 1970 FSM has a section on adjustment of the VR. They probably just threw it in there to put us off course 48 years later...

[Jim100]

Some of the problem could be that I'm not sure what I am using. The alternator has two blade connections and the flat style VR is wired between them. Parts I have bought were all 1970 listings at normal parts stores. The set- up worked fine for many years and just lately has been trouble.

[stumblinhorse]

You might pull the alternator and have it bench tested as well. A VR is a VR really. Not sure the year matters, I replaced mine with an electronic one, at least that is the one that finally worked. I used a vr706 from autozone.

[PwrWgnDrvr]

That is not how the 1970 VR works and it is NOT adjustable.

1970 is an isolated field alternator and the VR is in the circuit between the alt field and ground. The VR is an electronic unit that varies the resistance to ground, thus limiting current flow thru the field. Are you using an OEM VR or some aftermarket gizmo?

If you are using a std VR for a non isolated field system, its not going to work. They are not interchangeable. Most vehicles used the std system in those days and most regulators are for that type.

You are always very confident of this stuff, but the 1970 FSM has a section on adjustment of the VR. They probably just threw it in there to put us off course 48 years later...

Yes, the original FSM for 1970 does show the mechanical (adjustable) VR and the std single wire connected to the alternator field. THAT IS A PRINTING ERROR and that system was NOT USED on the 70/71 trucks!
They printed a supplement to the FSM to correct those errors and the 1970 FSM I ordered in 1978 directly from Chrysler in Detroit includes the supplement in the back between the Specs section and the Tightening Reference.
Unfortunately, that original error by Chrysler IS throwing you off course 48 yrs later.

A VR IS NOT A VR and that statement is evidence that you have no understanding of how the electrical systems function.
Page 22 of the supplement describes the Isolated Field Alternator and Electronic Voltage Regulator (non adjustable).
Here it is for your further enlightenment:
"The silicone transistor voltage regulator is a switching voltage regulator which regulates voltage by varying the duty cycle of a series of voltage pulses to the alternator field. The frequency of the voltage pulses is controlled by the ignition frequency of the engine, because the voltage regulator is a peak sensing regulator and the feedback from the ignition system is the highest level ripple on the car electrical system. Once the frequency of operation is established by the ignition system, the voltage regulator controls the voltage by varying the on and off time between the ignition firings. While the voltage across the field and and the current thru the output transistor is switching completely on and off, the field current of the alternator is only cycling thru incremental changes. Since the inductance of the alternator field has a relatively long time constant with respect to the operating frequency of the voltage regulator, there is only enough time allowed for an incremental decrease in field current thru the suppression diode during the off time of the transistor."

The supplement includes testing procedures and the correct wiring diagrams for the isolated field alternator and electronic voltage regulator charging system.

[PwrWgnDrvr]

Some of the problem could be that I'm not sure what I am using. The alternator has two blade connections and the flat style VR is wired between them. Parts I have bought were all 1970 listings at normal parts stores. The set- up worked fine for many years and just lately has been trouble.

If you have an intermittent short to ground on the green field wire, internally in the alternator on the field winding, or internally in the VR, the alternator output (voltage) will increase.
For example, if that green wire's insulation is compromised and the wire inside touches the engine or body, that is a short circuit that will increase the output. That wire could easily be touching the exhaust manifold, the insulation would melt and the short would be created.
Start looking and/or replacing parts.

[stumblinhorse]

Constant 15 at idle and 18-19 volts at speed is not an intermittent short. My point about a regulator being a regulator is just saying I looked all over for a replacement like what I had, the OEM Chrysler part. I ordered several of them and none worked. I picked up a solid state one that is nothing like stock 69-70 and it works perfectly and it was 1/3 the price.

The op can do whatever works, just passing on what worked for me after about 3 weeks of headaches.

[Jim100]

The VR that was on this truck when I got it and that worked for years is the flat style solid state. There is one like it out there that has a tiny screw on back that allows adjustment. Still solid state.
But yes I am going to do some wire work and clean up a bunch of splices that could be the issue.
I will have the alt looked at as well. Is there something in the alt that could make it disregard a working VR and pump out 19 volts?
Thanks guys for the help. Not my daily driver so not an emergency but still frustrating.
jim

[PwrWgnDrvr]

When I mentioned intermittent short, I was referring to the original post that started this thread where the symptoms were noted as intermittent.
The continuous high voltage mentioned was after a substitute (Delco) VR was installed. Not being the correct VR for the original circuit design it is no surprise that it is not working correctly.
The original problem was a brief, momentary anomaly, then ok for extended periods of time. The problem was compounded by a non compliant component substitution.
An internal short in the alternator can change output, but not likely to be only 19 volts. The voltage would go up and down dramatically with engine rpm. Removing the VR, grounding the field neg lead and increasing the rpm is how you can get 110V out of an alt to run power tools.

[Jim100]

The Delco was from rockauto for 1970 truck though. The voltage did spike which I mentioned in original post. That was with a oreily Chinese VR so I replaced with the delco and then it was 15 idle 19 with power. I will report back when I replace the wires to see if that fixes anything.

[PwrWgnDrvr]

When u measure the 19V is the battery absolutely fully charged?
If you're not sure, put a charger on it until the charger indicates it is, then start and measure. But it will take a minute or so to replace the current used to start it, so run it a bit before measuring. A less than perfect battery can also cause inexplicable readings.

[Jim100]

Will do.
Thanks for all the help and I will report back.

[Jim100]

Tested battery and alt. both good. Removed the brand new Made in usa Delco VR and stuck an oreilys china VR on and everything is right where it should be 14.3 or so volts . figures.
jim

[stumblinhorse]

Tested battery and alt. both good. Removed the brand new Made in usa Delco VR and stuck an oreilys china VR on and everything is right where it should be 14.3 or so volts . figures.
jim

Glad it was an easy fix.