PDA

View Full Version : Alternator, Wiring, or Regulator?


mrprostar
04-13-2008, 07:50 PM
First of all thanks to all of who have helped out this winter with various questions. Took our 96 Prostar out for the first time this year today and both speedos worked, teak looked amazing, etc., etc. The problem persists with the charging system. We had no charge at the end of last summer so we got the alternator rebuilt. I installed the alternator several months after taking it off and without a picture was not sure which wire went where. I have the orange wire on the large post and after reading several different threads on here determined the purple wiring to go to the EXC post. There is an S post and a few others down lower, also. Still no charge. Please advise on the wiring. Also, could we have a problem with the voltage regulator? I know the connection to the battery is fine because the orange wire and the battery have the same voltage. I know it is not charging because it reads about 11 and then slowly drops throughout the day and eventually doesn't have enough juice to start. I know there are a lot of threads about this but after hours of searching I couldn't find what I was looking for.

Engine Nut
04-13-2008, 08:13 PM
First of all thanks to all of who have helped out this winter with various questions. Took our 96 Prostar out for the first time this year today and both speedos worked, teak looked amazing, etc., etc. The problem persists with the charging system. We had no charge at the end of last summer so we got the alternator rebuilt. I installed the alternator several months after taking it off and without a picture was not sure which wire went where. I have the orange wire on the large post and after reading several different threads on here determined the purple wiring to go to the EXC post. There is an S post and a few others down lower, also. Still no charge. Please advise on the wiring. Also, could we have a problem with the voltage regulator? I know the connection to the battery is fine because the orange wire and the battery have the same voltage. I know it is not charging because it reads about 11 and then slowly drops throughout the day and eventually doesn't have enough juice to start. I know there are a lot of threads about this but after hours of searching I couldn't find what I was looking for.

I have attached a drawing that shows how your alt should be wired. Use the one labeled 55 AMP Prestolite alternator. You should have 12 V at the purple wire with the key switch in the on position. Charge your battery with a charger. A fully charged battery will read 12.6 volts across the terminals. Start the engine and rev it up to at least 1400 RPM and read the voltage across the terminals again. The voltage at this point should be at least .5 volts over the static reading you took earlier. If it isn't, read the voltage at the orange wire at the back of the alternator (with the engine still running). If the output at the back of the alternator is higher than the static voltage reading, you may have bad cables or a bad battery. If the voltge is not higher at the back of the alternator, you have a bad alternator.

mrprostar
04-13-2008, 10:19 PM
Thanks for your help. I am confused by your drawing, though. My alternator has five empty posts. Two at the top reading S and EXC and then two at the bottom with a red cover on one and a black cover on the other one and one larger post for the orange wire. Which of the other four posts does the purple wire go to?

Engine Nut
04-13-2008, 11:28 PM
I will check one in the morning and let you know what thestud for the purple wire is labeled. I suspect it is ESC but I will check for sure.

Engine Nut
04-14-2008, 09:17 AM
Thanks for your help. I am confused by your drawing, though. My alternator has five empty posts. Two at the top reading S and EXC and then two at the bottom with a red cover on one and a black cover on the other one and one larger post for the orange wire. Which of the other four posts does the purple wire go to?

Here is a photo of a 55A alt. I have called out the two connections for the orange and purple wires.