Ford 1920 alternator output

[MA1920]

Having electrical problem with Ford 1920.....see http://www.tractorbynet.com/forums/p...l-trouble.html I checked for more mice chewed wires....couldn't find any. When I turn the key to "on" it blows the fuse for the "quick start timer and voltage regulator circuit." I disconnected the timer, blew another fuse.

I then took some voltage readings:
tractor off, battery voltage: 12.5v
tractor running, lights off, battery voltage: 12.2
tractor running, all lights on, battery voltage: 11.95
tractor running I got the same readings at the alternator.
From what I've read, the voltages with the tractor running at 1500rpm seem low. What should the output be at the alternator?

Since the voltage regulator is internal to the alternator, can an electrical novice (me) test it?
Would a defective regulator cause the fuse to blow, since that particular fuse protects the voltage regulator circuit?

Any and all help apprecuiated.

Bob

[Hooked_on_HP]

Most auto parts stores will check your alt/reg. Take it off and take it in. If it is bad find a shop that repairs alternators or you can get one on ebay for$83. A replacement from N/H is $234.
Bill

[JC-jetro]

You might have issue with the rectifier bridge that changes AC to DC. As Bill said any Auto parts store can bench test your alternator for free. Just need to take Alternator off the tractor and take it to them.

JC,

[MA1920]

After work tomorrow I'll take off the alternator and head to AutoZone.

[MA1920]

After having the alternator tested at Auto Zone, it's good. The regulator and rectifier passed. If the alternator is good, why do my voltage readings seem off? If the tractor's running and I disconnect the negative or positive battery cable, will that prove anything?

Bob

[JC-jetro]

Bob,

That's good news. If you have bad connection then the resistance will go up in part of the circuit causing low voltage reading. You might also need to verify the calibration on your meter. Do you have another meter or can borrow a meter from someone else. It might be that your meter is giving you bad reading. Tractor will continue running if you take leads off the battery and that proves nothing. obviously you will not have lights.

JC,

After having the alternator tested at Auto Zone, it's good. The regulator and rectifier passed. If the alternator is good, why do my voltage readings seem off? If the tractor's running and I disconnect the negative or positive battery cable, will that prove anything?

Bob

[Hooked_on_HP]

Try unhooking your glow plugs or the timer. I wonder if the glow plugs are staying on .
Bill

[MA1920]

Bill And JC, thanks for your continued help. I did disconnect the glow plug timer and the fuse still blows. The fuse only blows when the instrument panel is connected to the main wire harness. The circuit board and instrument harness are new because the mice chewed some wires. The fuse that keeps blowing protects the "quick start timer and alternator regulator circuit." Since the alternator checked out ok, it's time to concentrate on the quick start timer circuit.

According to my service manual, the ignition quick start system is composed of the glow plugs, glow plug indicator lamp and timer relay. With the timer disconeccted the fuse popped, so the timer must be good.
The service manual has a more detailed procedure to check the glow plugs, relay and indicator lamp, but to test the circuit I have to turn the key to the "heat" position. As soon as I turn the key to "heat" or "run", pop goes the fuse. I'm lost. Any advice and direction greatly appreciated. Thanks again.

Bob

[jinman]

Bob, I've noticed that NH seems to wire the glowplug circuits in a similar manner. That said, the glow plugs on my TC45D get current from the main 40 amp fuse only. The timer controls how long the glow plug relay is energized. When the glow plug relay contacts close, they complete the path for glow current directly from the 40 amp Main fuse. It doesn't even go through the ignition switch. Technically, with the glow plug timer pulled, there is no way to energize the glow plug relay. If your relay is energized and powering the glow plugs with the timer removed, there is a wiring error I believe.

I wish I had a schematic for your tractor because I think I could point you in the right direction. My TC45D does not have a preheat position on the key switch. The glow plugs just automatically cycle each time the switch is turned from off to on. I don't want to mislead you, but that's how the glow plugs operate on my tractor.

[MA1920]

...I wish I had a schematic for your tractor because I think I could point you in the right direction....

Jim, what's the old saying? "Be careful what you wish for...." My service manual covers the 1920 and 2120. The wiring diagram for the 2120 has the color code, so I've been trying to match colors to the 1920 diagram. I hope it helps.

Bob