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I am trying to find some info on the alternator(?) on my 62 C60 fire engine. It is a Delco Remy 1117765-2B28. Did a internet search with no luck. It has an external regulator. There is no change in voltage change when running. If you remove the + cable on the battery while running, the engine dies.
I can't tell if the regulator is bad or the alternator. The reg looks suspiciously new. There is nothing on the L tab, alternator wire on bkt tab, and field on the f tab. I have forgot most of the theory that my Dad tried to teach me.
Thanks in advance.

That sure gives me a starting starting point. thanks

Did a check of the alternator with the battery lead disconnected and the engine running at about 1500 rpm (no tach). Only getting 1,7 volts out at the terminal with the neg lead to the neg battery post. This does not sound promising.

Most auto parts stores will test a charging system for free.

Do a full field test, that will tell you if the alternator is capable of charging.
To do this:
Insert a small screwdriver or other pointed object in the D shaped hole in the rear of the alternator. This will ground the rearmost brush forcing the alternator to go into full field mode. This will bypass the regulator and the alternator will put out 100%. If it charges doing this your alternator is good. If not then look at the regulator or the wiring.
Don

Don, thanks for the reply, will this test work on an alternator with an external regulator? Thanks

No, it won't work on an external-regulated alternator. Use the diagram provided above, and apply 12 volts from a known good source of battery voltage to the "F" terminal of the alternator. The voltage should go quite high, 15 volts or more, as the engine speed is increased.

BTW, NEVER- - -EVER RUN AN ALTERNATOR-EQUIPPED ENGINE WITH THE BATTERY CABLE DISCONNECTED!

The battery acts as a shock absorber in the charging system to dampen out voltage spikes. Disconnecting the battery while the engine is running can produce spikes in excess of 100 volts, and it can fry solid state circuits like rectifier diodes and radio amplifiers, etc. Not a good practice!

Here is whats todays testing revealed.

Engine off, key switch off, master bat on
Bat voltage to bat on reg and at alternator - 12.02 volts

regulator disconnected - continuity between bat tab and main coil, cont between main coil output and field coil

With everything connected 11.75v engine running

Engine running bat voltage to reg and 0 v to field output tab on reg.

edit checked the cont on the VR to ALT gnd - OK field fire - OK cleaned all contacts

Checked for voltage to the field output on VR -0v from bat tab or bat + key swich on motor not running

I will continue when the weather cools
off a little, over 100 outside

UPDATE:

Jumped the field from the battery and got 16.3 v run up the RPM and got 16.9 v. YEA, the alt appears good.

Engine off, key switch off, master bat on
Bat voltage to bat on reg and at alternator - 12.02 volts

SO looks like with key off the Regulator is powered.
With key on Regulator is off - ??.

Alternator with field from battery is output 16.3 volt. Next reconnect alternator and regulator and feed reg direct from battery. That should tell the final chapter n verse. Either miswired or bad reg?

Dan Bentler

It could be mis-wired. There was 2 wires on the field term - disconnected the unknown. there is nothing connected to the L tab.

Tested the alternator(ALT) the other day with good results. Down to the voltage regulator (VR).

This is a 3 tab VR labelled L, BAT, F

10 ga wire from battery to ALT term to BAT on VR. Good Ground from ALT case to VR case
Cont. Chk on Field (F) is good.

motor not running switch on
BATT Voltage(V) 12.02
V at ALT terminal 12.00
V at BAT term on VR 11.99
V at L term on VR 11.99
V at F term on VR 0.0

There was an 18 ga. wire originally attach to the BATT tab that I disconnected be cause it had 12V on it with the switch on or off,

Motor Running
V 11.8 at Battery
BAT tab on VR 11.75
ALT term 11.75
F on VR 0.0
L on VR 11.75

The gauge on the dash D|C does not move at any time.

I hate to change over to a modern style ALT, but it is starting to look like and option. The local parts house out here in the boonies wants about $50 bucks for a new 3 wire VR, no wiring diagram included.

Thanks for all the help