Help: Voltage Issue, regulator kinda not working?

[Mr.N]

Problem:
Charging system is over-charging.
- Car off I’ve 11.97 - 11.99 at the battery
- Car on I’ve 14.99 at the battery, 15.01 - 15.09 @ alternator positive post.
I charged the battery over night, still same readings as above. This is in Minnesota so were looking at 25-0 degrees Fahrenheit

Given:
1986 Dodge Turbo Z (2.2 engine)
Alternator just fried. Took it out, and tested it bad, Output voltage was bad.
Re-manufactured alternator installed and the problem showed itself.
- Do note: the Alternator was the same part number, however it was physically different I the back. I had to cut off the part plastic clip to get it to fit. (Can get picture if needed)


We’ll I’ve spend several hours reading some good post & info. Some linked below.
- Diagnosing Your Charging System Diagnosing Your Charging System
- check those grounds Post #6 voltage regulator question by gkcooper
- My Voltage jumped to 18V? by gkcooper
- How To: External Voltage Regulator voltage regulator help with notes by charger R/T
- voltage question by charger R/T

Field coil voltage results (seem low...)
No load 2.7 – 2.9 (Jumped around a lot)
light Load 4.1 – 4.3 (Jumped around a lot, had interior Fan & headlights on for load)
Heavy load 7.5 (Jumped around a lot, seen 6.9-7.9. Turn on everything)


From the Knize web page, I don’t’ understand the following “Check the voltage sense line to the logic module (make sure it is getting the same voltage seen at the alternator) and switching control circuit between the logic and power modules.”

What is the “Voltage sense line?”

Any hints oh how to get the voltage to under 14.7?
- I've another battery I could hook up...

[charger R/T]

I don't have diagrams for your year car but the voltage sense wire is the wire the computer uses to set voltage in the charging system. If there is a bad or dirty connection at the computer or high resistance in the wire the computer will read a low voltage. it will up the field current until it see the voltage that it wants to see. The desired voltage does change with temp. The computer has a temp sensor in the computer in live data it is listed as battery temp. The colder it is the higher the voltage. With living in Florida I really don't know its upper limit but I would bet 14.99 is above it. The low on a very hot day is around 13.5 to 13.6. A fulley vharged battery with the car off should be around 12.55. Cold can affect it.
Tim

[william]

What are you using to measure your voltage? What indicates that you are overcharging? While 15 seems slightly high, it isn't that far off from the generally accepted ~14.7. If no other overcharging symptoms are present, I would try a different meter to test.

[Mr.N]

Quote:

Originally Posted by william What are you using to measure your voltage? What indicates that you are overcharging? While 15 seems slightly high, it isn't that far off from the generally accepted ~14.7. If no other overcharging symptoms are present, I would try a different meter to test.

I'm using a Craftsman Digital Multimeter, that has worked well in the past. I'll see if I can find another... but it shows good levels on the other vehicle I've tried.

Found a pic of it on the web ->



As always I use dielectric grease on the connections for the Alternator.
I was thinking of removing the LM and greasing those connections... no?

[Mr.N]

Quote:

Originally Posted by charger R/T I don't have diagrams for your year car but the voltage sense wire is the wire the computer uses to set voltage in the charging system. If there is a bad or dirty connection at the computer or high resistance in the wire the computer will read a low voltage. it will up the field current until it see the voltage that it wants to see. The desired voltage does change with temp. The computer has a temp sensor in the computer in live data it is listed as battery temp. The colder it is the higher the voltage. With living in Florida I really don't know its upper limit but I would bet 14.99 is above it. The low on a very hot day is around 13.5 to 13.6. A fulley vharged battery with the car off should be around 12.55. Cold can affect it. Tim

Thanks for the reply.

The wire looks very clean on the Alternator side... time to check the other side.
However the computer was replaced this summer with another LM, and connections looked fine.
What about running another wire? a Jump wire from the alt to the LM?

[charger R/T]

Do you have a scanner available? What you need to do is compare what the computer wants it to charge at with what it is doing at the battery and what the computer sees as voltage. With where you are and the temps you need to see what the computer wants it to be. The meter you are using looks like a good meter a couple of guys at work use craftsman meters. I use a blue point and a vantage meter at work. I do compare them to each other quite often just to see they still read the same.
Tim

[Mr.N]

Quote:

Originally Posted by charger R/T Do you have a scanner available? What you need to do is compare what the computer wants it to charge at with what it is doing at the battery and what the computer sees as voltage. With where you are and the temps you need to see what the computer wants it to be. The meter you are using looks like a good meter a couple of guys at work use craftsman meters. I use a blue point and a vantage meter at work. I do compare them to each other quite often just to see they still read the same. Tim

I'm waiting on good guy to try his Dodge scanner...

Tried a new battery, same issues.

Get this... drive to work and the guage is at 15.? volts (or there about). Watch it all the 10 miles. Drive home, and bingo it's at 12 volts! As soon as I get home I jump out and take the voltage read.
measure the voltage... it's still at 15.0x from the battery and alt. However the guage is still showing around 12V ?