Replaced alternator now voltage is too high? 15.5v

[nm9stheham]

It is a bit higher than it should be but it is at least regulating; getting better! Should be in the 13.7 to 14.4 range and will tend to be on the higher end when cold. I think the issue is that there is still a bit too much voltage drop from the alternator output and battery +, and the ignition feed to the VR. Try it again with this set up, and measure what is going into the + field terminal and into the regulator; I bet it is down around 12.6 to 13.6 volts and it should be higher. After that, you need to check voltage to the ignition switch and then back out to the VR and field + to see where the voltage drops are occuring.

Also, turn on the headlights and blower and see what the alternator output voltage does.

 

[GearAddict]

I took a couple of quick measurements last night.

Batt reads 12.65v

Ignition wire measured at the VR connector (unplugged from the VR) 12.45v in run position with engine off.

+ Field terminal at Alt to ground on battery, with everything connected, in run position, engine off... 11.8v? (same when checking to ground on VR)

+ Field terminal at Alt to + term on battery, with everything connected, in run position, engine off... 0.7v

From what I have learned seems, like we are getting closer to the problem... 0.7v drop needs to be solved

I took one more measurement though.... resistance from VR connector to Field connector with everything unplugged and I got 0 Ohms... I thought surely I would see an issue here to account for the .7v drop, especially since it is ony a 12" long wire. I need to check the voltage at the end of this connection when not plugged into the Alt and see if it is higher.

Could the Alt be pulling the voltage down? When I re-measured the field terminal to ground it showed it as open (no resistance reading, or too high for the meter to read).

Much thanks for all the help, this has certainly been a learning experience for me.

BTW the ford style regulator, which I set aside thinking I could get the Mopar one to work easily, seems like it might be a better set-up since it utilizes the remote voltage sensing and would move the sense voltage closer to the batt and alt output.... I may experiment with that later, but I'd like ot get the mopar one working first.

 

[nm9stheham]

OK, the battery voltage at 12.65 shows a good charge.

When you say 'at the VR connector', do you mean at the VR connector lead that connects to the field + or at the VR connector lead that connects to the field - ?

The 0.7v drop to the VR terminal (or thereabouts), makes sense with the higher than normal output that you are seeing when running.

As I understood it, you have the VR power terminal tied directly to the field + terminal; so 0 ohms should be the reading. And the field resistance is very low, so even if you were at the other end of either, then the reading would be near to 0 ohms anyway.

The drops are likely in the ignition switch area, or the bulkhead connections. YOu need to take readings all along the circuit from batt to starter relay to ignition switch in and ignition switch out and at the bulkheads. If you have the blower on, it will be worse. What do you have for bulkhead connections, and for the ignition switch? Is it a new switch? Are all ther wire straigth runs, or are there any crimped in splices anywhere?

 

[GearAddict]

Thanks to everyone for the help, especially nm9stheham for sticking with me through the troubleshooting... I had to take a few days off from working on it as I was getting frustrated. I'll be back at it tomorrow.

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When you say 'at the VR connector', do you mean at the VR connector lead that connects to the field + or at the VR connector lead that connects to the field - ?

Field +

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The 0.7v drop to the VR terminal (or thereabouts), makes sense with the higher than normal output that you are seeing when running.

I pulled al the conectors apart and recrimped (I may solder some this weekend) and got it down to .3V drop when measuring at the Alt end of the + field wire, with it disconnected from the alt. But still charging around 14.9-15v

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As I understood it, you have the VR power terminal tied directly to the field + terminal; so 0 ohms should be the reading. And the field resistance is very low, so even if you were at the other end of either, then the reading would be near to 0 ohms anyway.

Yes, should be 0 ohms, I thought I might see more as I was hoping this was where the bad connection was (poor crimp = some higher ohm reading).

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The drops are likely in the ignition switch area, or the bulkhead connections. YOu need to take readings all along the circuit from batt to starter relay to ignition switch in and ignition switch out and at the bulkheads. If you have the blower on, it will be worse. What do you have for bulkhead connections, and for the ignition switch? Is it a new switch? Are all ther wire straigth runs, or are there any crimped in splices anywhere?

I'll go back through all of this this weekend... thanks again for the help, I'll get it resolved one way or another on Sat.

 

[nm9stheham]

Check your meter for accuracy.... buy a couple of new 9v transistor batteries in separate stores or make sure you get some with recent date codes. They should measure 9.6 to 9.7 volts when new. (But your charged battery showing 12.65 volts after a good charge and then a few hours of 'rest' ('rest' means the charger and all other connections removed) tends to say your meter is accurate.)

0.3v drop is good enough in that area with engine not running. Now re-measure the voltage at the VR input and at the field+ with the engine running.... and everything connected up. You need to see if the field and ignition coil when pulling running current is causing additional voltage drop. If so, then go through it again to find where. Tedious ... but it will pay off on the long run.

 

[GearAddict]

PROBLEM SOLVED! Ok, so I never did figure out the mopar style regulator issue that had me running at 15v.. Even with it running and full load, I could never account for more than a .3v drop after I recripmped and soldered all connections...


I broke down and went back at the ford/chevy style remote voltage sensing route that we discussed before. Relocated the battery feed line from the alternator to the remote power junction stud I have on the firewall and then ran a new sense line from that to the ford style regulator and presto! 14.3 - 14.4 volts at the battery!

Added bonus of running it from the Junction is that it is a pretty consistent 14.3 - 14.4 volts everywhere I measured in the system and the dash gauge concurs.

Big thanks to everyone for all the help. Much appreciated.

 

[nm9stheham]

Cool! Glad to hear it. There must have been some serious drops betweeen the alternator output and over to the battery and then on to the stud. I bet the Mopar system would have worked better this way too. Congrats!