How to test Bombardier J5 alternator and regulator

[jflarin]

Hi,
I have a Bombardier J5 that developped a new problem: it does not want to start all the time. In fact, the starter relay engages but the started does not turn.
While investigating that, I found that battery voltage is pretty low even when the engine is running (12.3 V). I'd expect the alternator to push that voltage higher to recharge the battery (which may explain why I have starting problems...)
In any way, i found this schematics which looks pretty much like the wiring of the actual machine:

Anybody knows what voltage to check on what wire? Having 3 red wires going to the alternator does not make it easy to identify what are A F and G wire, but knowing what those mean could help.
Thank you for any and all help,
jf

 

[zspryte]

Bad batteries often have low voltage that even a got alternator cannot increase. You might try a good battery and see how things look. Hate for you to fix something that isn't broken.

 

[zspryte]

F - field circuit ; G - ground ; A - ampere
The A wire is normally the largest gauge wrie as it is the output that goes to the amp gauge and battery. The voltage between this wire and the battery ground should be 13.5 to 14.5 volts or even slightly higher.

 

[jflarin]

Finally debugged the issue today using old books (Dodge/Plymouth from around 1955). Here is the information if anybody is looking for it. FLD is the field and if you short that wire to battery negative pole, the generator (identified alternator on the picture above) will start generating 22 V to 26 V on the A terminal (Armature from what I read) at the speed my engine was running today. That confirms that the generator is working and that the regulator is not driving the field signal correctly.
Looking at the schematics of the regulator, and looking at the intermittent spark between the regulator and the frame of the J5, I figured that the regulator casing has to be WELL CONNECTED to frame ground so it can connect the field terminal to battery return to increase the produced voltage by the generator.

jf

 

[J5 Bombardier]

If it gives you problems again , consider switching over to a single wire GM alternator. They are easy to wire in , less hassle with the internal regulator.
J5 Bombardier

 

[Tacoman]

Agree with J5, I have done a couple. Use either a Delco 10si or a 12si. Both are internally regulated, no external voltage regular in the system. Both run about $80 on Amazon. The internals are pretty much the same but one may physically fit better than the other. There are some retrofit mounting brackets available. You can buy either alt as a single wire (self exciting) or a three wire setup. Make sure you get the right one for your intended use. Some will work with either a 1 or 3 wire but usually you have to choose.

Pro's for single wire:The single wire is a little easier to wire. Cons for the single wire: You will need either an ammeter or a voltage meter to verify that it is charging. Idiot light is not an easy option. You will need to run it at about for a moment at 1000-1200 rpm at the alternator for it to start charging. Once it starts charging it will keep charging even at low rpm.

Pros to three wire: You can easily wire an idiot light into the system. From the schematic, it looks like your system has only an ammeter. You can add an idiot light, which is not a bad idea for a vehicle you do not use regularly. If you want an idiot light, either get an incandescent or make double sure you have the polarity on the LED correct. It is not very obvious what the correct polarity should be. Install a diode in the charging circuit to prevent the engine from running after the ignition is switched off. Instant charging at low rpm, no engine reving required.

There is plenty of more detailed information on the web if you do some Googling. "Mad Electric" has some pretty good information but their parts are pretty expensive.

 

[vintagebike]

if only the High Schools still had wood shop, auto shop and home economics. Closest I got was my Dad buying me a worn out B/S rototiller engine. He saiid "If you want a Go-kart you will need to fix this beauty first". Fixed it but never got the kart. Sold the engine and started a neighborhood lawnmower repair business. Used the money for skiing at Sugar Bowl where I saw my first SnoCat.