Voltage all over the place

[Vossie]

so here’s an interesting one for you guys:

Original 12v alternator from my 2F. Wiring harness left largely in tact. Original voltage regular.

So when I first start the 45 up, it takes a few minutes for the voltage to come up to 14.8. Like it will hover around 12.3 or even go down as low as 11 at idle. If I use the indicator in conjunction with my radio during this low voltage then it goes down to 10.1 and my radio switches off.

And it goes just crazy when I use my lights or my wipers.

Strange thing is that after a few minutes of driving it will just come right and everything will be fine until I switch the car off again.

One of the ways I track what’s happening is I have a tachometer that is driven off the W signal from the alternator. It behaves fine when the voltages are normal, but doesn’t read correct when the low voltage is around.

Any one have any ideas? Bad regulator?

 

[Michael B]

Vossie it sounds like the alternator isn't charging until the engine has achieved the proper RPM for the field exciter to pickup. This is reminiscent of the issues old hotrodders have in running a single wire setup on a GM alternator. Check for loose connections on your regulator. You may also have a failing regulator.

 

[Vossie]

Vossie it sounds like the alternator isn't charging until the engine has achieved the proper RPM for the field exciter to pickup. This is reminiscent of the issues old hotrodders have in running a single wire setup on a GM alternator. Check for loose connections on your regulator. You may also have a failing regulator.

been suspecting my regulator for a while now. you think putting in a new one will fix my issues, or is there a chance it may have something to do with the alternator itself?

 

[Michael B]

Is your alternator internally regulated?

 

[4x4veteran]

Check belt tension. It could be as simple as a loose wire inside. Had that happen once. As always check the grounds. Could be the regulator.

 

[lc69hunter]

Vossie it sounds like the alternator isn't charging until the engine has achieved the proper RPM for the field exciter to pickup. This is reminiscent of the issues old hotrodders have in running a single wire setup on a GM alternator. Check for loose connections on your regulator. You may also have a failing regulator.

I am running one of those on my 40. It is a pain at times, and you have to kick the rpm up to approx 1500 for it to start charging.

What is the alternative?

 

[Michael B]

You would have to wire a "load" to the alternator field terminal. A load would be anything electrical that draws power when the key is on.

 

[jm599]

The seal around the cover of the VR can sometimes let in dirt. Easy to clean the contacts with cover off. Saved me one night in Black Hills.

 

[Solace in Solitude]

You should be able to adjust the VR... Rudi (@bj40green ) has great information/instructions HERE.

IIRC Rudi also told me the VR doesn’t allow the alternator to actually charge, unless you are running about 2000rpm.

Hope all is still well in Zimbabwe.

 

[Vossie]

Is your alternator internally regulated?

no, usual external reg as stock on the 45

Check belt tension. It could be as simple as a loose wire inside. Had that happen once. As always check the grounds. Could be the regulator.

belts up to tension. also that wouldnt explain why it doesnt work and then it does, would it?

I am running one of those on my 40. It is a pain at times, and you have to kick the rpm up to approx 1500 for it to start charging.

What is the alternative?

it hasnt given me this kind of trouble in the past though. normally will charge, albeit with slightly lower voltage but still in spec.

You would have to wire a "load" to the alternator field terminal. A load would be anything electrical that draws power when the key is on.

would the fuel gauge be enough of a load? i also have other aftermarket gauges that come on with a different master that i flick up once the motor is running.

The seal around the cover of the VR can sometimes let in dirt. Easy to clean the contacts with cover off. Saved me one night in Black Hills.

thanks. checked it out. theres a bit of rust in the VR, so i cleaned the contacts up. unfortunately it has really done anything. so i may be looking at a in process of dieing VR

You should be able to adjust the VR... Rudi (@bj40green ) has great information/instructions HERE.

IIRC Rudi also told me the VR doesn’t allow the alternator to actually charge, unless you are running about 2000rpm.

Hope all is still well in Zimbabwe.

ja, i have had to adjust this VR before. it wasnt giving enough voltage about 6 months ago so i adjusted it back into spec as per FSM.

all good here in Zim. its just another day on the ground. at least the trading rates on US cash are coming down. good signs for us

 

[Michael B]

Vossie,
I would have the alternator tested, either on or off of the truck. If it tests good I would replace the VR.

 

[RAYJON]

I would bet the brushes in the alternator are warn out, cheep fix if you can solder.. i would rebuild the alternator.. have had bad luck with parts house rebuilds.. so i just do my own..

 

[Pin_Head]

1. It depends on where you are measuring the voltage at. If you are not measuring it at the battery itself, You can get a false reading if there is a high resistance connection between the battery and the remote location you are measuring. The higher the current, the greater the voltage drop.

2. Anything lower than 12 V at the battery indicates that the battery is discharged whether or not the alternator is working.