Replaced alternator now voltage is too high? 15.5v

[GearAddict]

My 69 RR was not charging except at high RPM so I swapped out the alternator for a new one.

The bad one was a square back 3 terminal unit, so I picked up a new one from Pep boys for a 72 Satty. After hooking everything up same as before (1 field wire to regulator and 1 to ground) my dash gauge is now reading 15.5v at idle.

I'll check directly at the back of the alt today, but assuming that it still reads 15.5, should I suspect the VR?

I should say that I rewired the car using a Ron Francis kit and the car has never charged properly..I'm using Ron Francis VR that they suggest using.

 

[Basket case]

I've always replaced the VR whenever replacing the alt. and remember, just because a part is new (or reman) ,it can be bad out of the box. The IH truck dealer I worked at handeled Delco Remey starters and altornaters. A few times we'd have to go thru a stack to find one good one.

 

[GearAddict]

Thanks Dave... So you're thinking it might be the alternator then? The old one was putting out next to nothing at idle - 2000RPM and 14.5 at 3K but I also don't know that it was delivering the amps, because I could drive it for 3 miles and then when I'd go to start it again the batt would barely turn the motor over.

Anyone know what VR should be used with this combo? ('72 Alt, MSD Ign)?

I have a newish Optima batt and I made sure it had a full charge prior to running the new Alt for the first time.

 

[69a100]

Note the first dot note in the "early charging system modified to use 70 style VR". http://www.imperialclub.com/Repair/Electrical/charging.htm

 

[Cranky]

How's the battery? Have you put it on a charger and let it charge up to full? How bout having it load tested? Most auto parts houses will do that for free. In order to diagnose charging problems, you need to start out with a good battery but you can also have the alternator checked at the same auto parts house....

 

[Basket case]

and don't rule out a broken wire. I hate electrical.

 

[nm9stheham]

The alternator is not the problem if it is charging that high; the alternator is working. See what it charges at at fast idle, probably is closer to 16-17v. Don't run it long like this or it can boil the battery dry.

Your problem with the 2 field wire alternator is that either:
1) the regulator is commanding the alternator to full, unregulated output; this is often due to too low a voltage getting to the voltage regulator power feed and the VR always thinks the system voltage is too low.
2) something is grounded on the control line of the field wire (which will make the alternator put out full juice) and the VR is losing control of the alternator due to this
3) VR is internally shorted
4) there is an internally ground on one lead of the alternator
4) the system is miswired or possibly there is a bad VR, connection ground or otherwise. SInce this has never worked right, this is the likely issue and it took out the 1st alternator.

Is this a VR-88 model regulator?

First, disconnect both field wires from the alternator and measure the resistance from both terminals to the alternator case. This should be avery high reading (many thousands of ohms), but if it is very low then there is a ground on one end of the field. Sometimes these come bad from the rebuilder. But this is not likely it, IMO; it just needs to be checked to eliminate this possibility.

Then, with your voltmeter and the field wires reconnected, measure the voltage at both small field terminals on the back of the alternator while running, referenced to battery -. It should read very close to battery + voltage on one terminal, and a few volts lower on the other. But, I bet you will find that one wire is at full voltage and the other is 0 or close to 0. Please let us know what you measure.

BTW, I can't find wiring diagrams for this Ron Francis system to help in this; if you know where to look, let me know.

 

[Michael789]

Which Ron Francis kit did you go with? I'm asking because I'm considering buying one for my 71 satty.

 

[GearAddict]

The alternator is not the problem if it is charging that high; the alternator is working. See what it charges at at fast idle, probably is closer to 16-17v. Don't run it long like this or it can boil the battery dry.

Your problem with the 2 field wire alternator is that either:
1) the regulator is commanding the alternator to full, unregulated output; this is often due to too low a voltage getting to the voltage regulator power feed and the VR always thinks the system voltage is too low.
2) something is grounded on the control line of the field wire (which will make the alternator put out full juice) and the VR is losing control of the alternator due to this
3) VR is internally shorted
4) there is an internally ground on one lead of the alternator
4) the system is miswired or possibly there is a bad VR, connection ground or otherwise. SInce this has never worked right, this is the likely issue and it took out the 1st alternator.

Is this a VR-88 model regulator?

First, disconnect both field wires from the alternator and measure the resistance from both terminals to the alternator case. This should be avery high reading (many thousands of ohms), but if it is very low then there is a ground on one end of the field. Sometimes these come bad from the rebuilder. But this is not likely it, IMO; it just needs to be checked to eliminate this possibility.

Then, with your voltmeter and the field wires reconnected, measure the voltage at both small field terminals on the back of the alternator while running, referenced to battery -. It should read very close to battery + voltage on one terminal, and a few volts lower on the other. But, I bet you will find that one wire is at full voltage and the other is 0 or close to 0. Please let us know what you measure.

BTW, I can't find wiring diagrams for this Ron Francis system to help in this; if you know where to look, let me know.

Thanks... I just got home and did a quick check, so I can answer some of the questions.

Yes it is the VR-88 regulator.

The original alt was a 2 field alt, but the previous owner had only 1 field wire hooked up. I grounded the second field wire but still charging only at higher RPMs.

When I went to install the new alt, I realized that the main red power lead from the alt to the battery was loose, this may have been the problem in the first place. I didn't bother to tighten down and check before I swapped it out for the new one.

The battery was left on a trickle charge until full and is reading 12.65 volts

I checked the resistance from negative batt terminal to case ground on the VR and it reads 0.3 ohms (less than 1 ohm) I suppose this could be better, but I wouldn't think that was a bad ground connection.

The resistance between the 2 field wires was 166k ohms.

I haven't checked the voltages on the field terminals yet.

I am on my way to the auto parts store now, to pick up a new VR. I will take my old alt with me and my battery and have them check both.

- - - Updated - - -

Which Ron Francis kit did you go with? I'm asking because I'm considering buying one for my 71 satty.

I went with the Access 24/7, but I actually would not buy that specific kit again for 1 reason... The connections at the fuse block are all hard wired which means you have to be perfect with your cable runs, because if you end up with too much slack after you terminate the ends, you can't shorten them up without cutting and splicing. If I had the dash out of the car when I did it, maybe it wouldn't be so bad, but I didn't and it was a pain in the butt. I would however recommend Ron Francis kit from a quality standpoint, it was a good kit overall. I would recommend the Express series, as it is basically the same except with screw in terminations.

 

[GearAddict]

Just got back from Napa, with a new VR 428 which Ron Francis says is a cross for their VR-88.

Also had them check the old alt and they said it was toast.

 

[Basket case]

well something has toasted two alternators....better find out what before you toast another one.

 

[GearAddict]

well something has toasted two alternators....better find out what before you toast another one.

Only one bad Alt... Same one that was in the car when I bought it... The new one has only been run for a 1-2 mins total, I shut it off when I got 15.5v on the dash gauge. As far as I know it's fine.

I just swapped in the new VR and ran a separate ground wire to ensure it's well grounded. I'll fire her up shortly and see what's what.

 

[nm9stheham]

OK, good on the readings. Ground resistance is hard to measure any better than that with a standard meter. And good deal on the reistance from the field wires to the alternator case (which is how you measured the filed reistance of 166 kohms, right?). That means that there is no internal ground in the field.

Don't hook up and test anything yet... there is new info to consider. OK, on the VR428; I just looked at that and now I know why the VR88 connector looked familiar; it is an old 60-70-80's vintage Ford regulator. We need to check the wiring to that first. (And BTW, these Ford regulators tended to blow anytime you disconnected the battery with the car running...so don't do that!)

Okaaaay....well I dug out an old Ford regulation diagram, and here is one thing important: The Ford regulates like the older 1 field wire Mopar alternators, not the later 2 wire ones. This can be done but it will take some checks of the wiring.

The connections into the VR looking at the connector are, left to right, should be:
I - A - S - F
Please see if your VR428 connections have these letters so we can be sure of the order.

There are more details but basically the wiring looks like it needs to be:
1 of your 2 field terminals on the alternator needs to be grounded
The VR's F terminal connects to the other field terminal on the alternator
The VR's I terminal needs to connect to the ignition wire going to the ballast and that also normally feeds to the Mopar regulator (either type); it will have +12v on it when the ignition switch in in the RUN position.
The VR's A terminal connnects to the alternator output
The VR's S terminal has no equivalent in the Mopar world. It will connect to either the alternator output or the ingition +12v feed like the I terminal. I would start with the latter. This is the one are I am murky on.

You're going to have to trace out the wires from the VR connector to see if they go to the right places and check that the voltages are right on those connections.

 

[GearAddict]

OK, good on the readings. Ground resistance is hard to measure any better than that with a standard meter. And good deal on the reistance from the field wires to the alternator case (which is how you measured the filed reistance of 166 kohms, right?). That means that there is no internal ground in the field.

Don't hook up and test anything yet... there is new info to consider. OK, on the VR428; I just looked at that and now I know why the VR88 connector looked familiar; it is an old 60-70-80's vintage Ford regulator. We need to check the wiring to that first. (And BTW, these Ford regulators tended to blow anytime you disconnected the battery with the car running...so don't do that!)

Okaaaay....well I dug out an old Ford regulation diagram, and here is one thing important: The Ford regulates like the older 1 field wire Mopar alternators, not the later 2 wire ones. This can be done but it will take some checks of the wiring.

The connections into the VR looking at the connector are, left to right, should be:
I - A - S - F
Please see if your VR428 connections have these letters so we can be sure of the order.

There are more details but basically the wiring looks like it needs to be:
1 of your 2 field terminals on the alternator needs to be grounded
The VR's F terminal connects to the other field terminal on the alternator
The VR's I terminal needs to connect to the ignition wire going to the ballast and that also normally feeds to the Mopar regulator (either type); it will have +12v on it when the ignition switch in in the RUN position.
The VR's A terminal connnects to the alternator output
The VR's S terminal has no equivalent in the Mopar world. It will connect to either the alternator output or the ingition +12v feed like the I terminal. I would start with the latter. This is the one are I am murky on.

You're going to have to trace out the wires from the VR connector to see if they go to the right places and check that the voltages are right on those connections.

Correct, very high reading from ground on the alt case to either field terminal.

1 field terminal is grounded

The voltage regulator is wired as follows...

I - unused
A - 12 volts from ignition in run position...confirmed voltage 12.28VDC
S - jumper in connector to A above, 12v from ignition
F - connected to field terminal on alt

Looks like the VR428 is a mechanical regulator and the VR 88 is solid state, but the pin outs are the same.

I have a solid state mopar regulator lying around as well and had thought to just convert over to that, but it don't have the connector for it.

What will be the difference connecting the A term to the Alt vs ign, won't the both have the same voltage levels?

 

[daredevil]

Maybe the sensing wire. A good read here.http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

 

[nm9stheham]

OK, sounds like it was set up right. The connections you describe above ought to work, based on the older mechanical regulator schematic here; the I line was used in the older systems for the idiot light system to indicate an alternator problem (and provide low startup voltage to the regulator in the Fords; see below) but the Mopar has the ammeter for a trouble indicator.

The one issue with connecting the A line to the ignition switch output is that any voltage drop in the ignition switch circuit will cause the regulator to command the alternator to a higher output. For example, if there is a 1 volt drop in the ignition line, then the regulator will have to command the alternator to a 1 volt higher output to compensate and get the right voltage back to the regulator A input. (This is possible problem 1) in my 1st post.)

At this point, I would re-check the wiring and start up and see what you get. And then measure what voltage is coming out of the alternator power output and what is going into the A terminal. If it is more than .3v lower, then find where this drop is occuring. If the A terminal was rewired to the big bolt lug on the starter relay, then these voltage drops would be eliminated.

Did you rewire the entire car or just the engine bay compartment? I am wondering since the orignal ignition switch and connector, and the bulkhead connectors are good spots for voltage drop problems.

And BTW, with the Ford type alternator, wired as you have it or as I first listed, if you put the key in RUN but don't start the car, there will be significantly higher than normal current flow into the regulator and into the field. So, you should be careful to not leave the key in RUN very long when the car is not running. The orignal Ford system design managed this situation by sending low voltage to the regulator in this condition (key in RUN but not running) via the idiot light resistance in the I line. The S line from the alternator was then used to switch full voltage into the regulator via the A terminal when the alternator started putting out. There is no S terminal on Mopar alternators, so we can't do this.

 

[GearAddict]

Maybe the sensing wire. A good read here.http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

Thanks Daredevil, that might just be the answer to my question above about why not use the ign 12v on the S terminal and also may be the issue here altogether.

If the VR is using the 12v from the ign it may have some serious voltage drop going on causing the voltage regulator to put out a higher voltage?

Total cable run from alt output to VR sense wire right now is alt 7 ft>Batt 3 ft>remote stud junction 3 ft>fuse block 2ft> ign 2ft> fuse block 8ft> VR

I actually have a remote power stud located on the firewall, but I have the alt output going to the batt and then a feed from the batt to the remote stud and then all electrical is running from the stud in own way or another (except starter which is straight from the batt).

Seems like if I ran the voltage sense wire to the stud and then had the alt output go to the stud as well, it might be more consistent and possibly solve the issue.

Alt 5 ft > junction stud 5ft> VR

- - - Updated - - -

OK, sounds like it was set up right. The connections you describe above ought to work, based on the older mechanical regulator schematic here; the I line was used in the older systems for the idiot light system to indicate an alternator problem (and provide low startup voltage to the regulator in the Fords; see below) but the Mopar has the ammeter for a trouble indicator.

The one issue with connecting the A line to the ignition switch output is that any voltage drop in the ignition switch circuit will cause the regulator to command the alternator to a higher output. For example, if there is a 1 volt drop in the ignition line, then the regulator will have to command the alternator to a 1 volt higher output to compensate and get the right voltage back to the regulator A input. (This is possible problem 1) in my 1st post.)

At this point, I would re-check the wiring and start up and see what you get. And then measure what voltage is coming out of the alternator power output and what is going into the A terminal. If it is more than .3v lower, then find where this drop is occuring. If the A terminal was rewired to the big bolt lug on the starter relay, then these voltage drops would be eliminated.

Did you rewire the entire car or just the engine bay compartment? I am wondering since the orignal ignition switch and connector, and the bulkhead connectors are good spots for voltage drop problems.

And BTW, with the Ford type alternator, wired as you have it or as I first listed, if you put the key in RUN but don't start the car, there will be significantly higher than normal current flow into the regulator and into the field. So, you should be careful to not leave the key in RUN very long when the car is not running. The orignal Ford system design managed this situation by sending low voltage to the regulator in this condition (key in RUN but not running) via the idiot light resistance in the I line. The S line from the alternator was then used to switch full voltage into the regulator via the A terminal when the alternator started putting out. There is no S terminal on Mopar alternators, so we can't do this.

Thanks! I must have been typing while you posted this. Sounds like I'm on the same page. I'll run some some tests and post back my findings.

I rewired the whole car.

 

[nm9stheham]

Yeah, I like the idea of taking the alternator output to the power stud. It's output current can split at that point to feed the battery and to feed the other circuits separately. The only line that then carries the full alternator current is the one from the alternator to the stud. And the stud would be a good point to connect the A line.

Take note on the info to not leave the key in RUN too long while not actually running; I have used these old Ford regulators used like this and one of the internal wirewound resistors gets overheated and will blacken and fail if you're not careful.

 

[GearAddict]

Ok just ran an experiment with the old mopar style regulator I had sitting around ( unknown if good or bad). It's a solid state type.

Wired it exactly as shown in the 70 and up diagram here the last diagram http://www.mymopar.com/charging.htm

Ign feed and field wire spliced together crimped together into a bullet style female connector. And hooked to the + field terminal as shown. And then bullet conn from VR to -field term as shown. Regulator case grounded.

Started her up and within about 5 seconds the voltage started to skyrocket! 18v and counting when I shut it down.

As I said, it was unknown good or bad VR but I didn't expect that to happen.

Not sure what is the issue, think I might go pick up a new one I try it, but did I do something wrong? All connections are good.

I did notice with the ign in run position but engine off that I get 12v on both field terminals. I expected it on the + field terminal since it's wired together with the ign 12v, but since I have been running the neg field term to ground in the other sit-ups, I am not sure if I should see 12 v there as well

 

[GearAddict]

Ok, picked up a new mopar regulator, hooked up same as above.. Measured at the battery, the voltage runs between 14.6-15v depending on the rpm. Is this still too high? Or should I be measuring at the alternator? I would assume that would be higher than at the bat not lower.

Other than going back to the Ford style VR and rewiring as I listed a couple of posts ago, I'm not sure what else could be wrong? Seems like everything is hooked up correctly and everything is new.

Thoughts?