CAT 416c tach & hour meter

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Hey, my tach and hour meter stopped working suddenly. I checked continuity from tach and hour meter to alternator and its good. Power and ground is good. Serial # 4ZN02115. What am I missing? Also, what year is this 416c? Thanks in advance

 

[Nige]

Do you have an electrical schematic.? If not, do you want one.?

Your machine was built April 1997.

 

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I have the parts manual but not any schematics, so yes I would love one. Any advice on where to start since the simple check of continuity checks out?

 

[Nige]

I'll send you the electrical schematic. Keep an eye on your messages.

I have the parts manual but not any schematics, so yes I would love one. Any advice on where to start since the simple check of continuity checks out?

Not really. But if you locate the tachometer & hourmeter on the schematic and start working back towards wherever the power/signal comes from you should find something common.

 

[edgephoto]

I do not have a schematic in front of me but you could check the Tach output on the alternator.

 

[backspacer]

I do not have a schematic in front of me but you could check the Tach output on the alternator.

I have checked continuity to tach from alt and its good. If there is supposed to be some other type of signal, let me know how to check it please.

 

[backspacer]

I'll send you the electrical schematic. Keep an eye on your messages.

Not really. But if you locate the tachometer & hourmeter on the schematic and start working back towards wherever the power/signal comes from you should find something common.

Thanks for the schematic. After a simple trace, the single wire has good continuity to both the tach and hour meter. It's one wire from the alternator that splits into a Y under instrument panel that then goes to tach and hour meter. What type of signal is coming from the alt? Is there some other way I should check instead of just continuity?

 

[Nige]

I have checked continuity to tach from alt and its good.

Have you checked the wire under load using a test light connected to/from batt+ & ground.?

You will need to disconnect wire 450 Yellow at both the alternator end and the service meter/tacho end.
It's not unknown for a wire to show continuity on a multimeter because it literally only needs one strand to do that, but put a load on it and it breaks down.

 

[Coaldust]

OP,
What kind of signal, you ask?

You will be looking for an A/C signal in the 0-30volt spectrum that changes with engine rpm.

Don’t get wrapped around the axle on actual voltage. You either have a fluctuating signal, or you don’t. If you don’t have a signal at the Alternator tachometer terminal, most common is a bad diode trio. Because that’s how the stator tap gets to the tach terminal.

 

[backspacer]

OP,
What kind of signal, you ask?

You will be looking for an A/C signal in the 0-30volt spectrum that changes with engine rpm.

Don’t get wrapped around the axle on actual voltage. You either have a fluctuating signal, or you don’t. If you don’t have a signal at the Alternator tachometer terminal, most common is a bad diode trio. Because that’s how the stator tap gets to the tach terminal.

The yellow wire that runs straight to the hour meter and tach has nothing on it. I checked right at the connector on the alternator and nothing, even when reving up the engine. You say a bad diode trio? Where is that and is it replaceable or do I need a new alternator? Thanks

 

[Nige]

You say a bad diode trio? Where is that and is it replaceable or do I need a new alternator?

I would say #6 on the attachment but the electrical experts should confirm that.
This is providing your alternator is OEM and has not been replaced with a "will fit" at some point during the life of the machine.

 

[Coaldust]

You have a few ootions. You could take the alternator apart, replace the diode trio and install new brushes while you are in there. You could purchase a replacement or have your favorite electrical shop rebuild it.

 

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so I got the rectifier (top part in pic) and regulator off (bottom part in pic). Is there a way to check to see which one is bad? The connector that goes to the tach and hour meter plugs into the regulator. I can't find the rectifier anywhere online except for CAT, about $120. Haven't searched for the regulator. Best guess as to which is bad?

 

[Coaldust]

You can check the diodes in the rectifier bridge individually with an DVOM w/diode test feature. They should have about .5v of voltage drop.

You can even check the VR by using a 12 volt car battery, DVOM,some jumper wires and a battery charger.

It’s too much for me to peck out with my smart phone. There is a ton of YouTube videos that demonstrate it.

 

[edgephoto]

How To Test an Alternator Using a Voltmeter | Moss Motors

mossmotors.com

Alternator diode testing - AutoEdu - procedure

The test of diodes is reduced to checking their ability to pass current in only one direction. The measurement can be done with a multimeter.

autoedu.info

A couple resources to show you how they can be tested.

 

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Looks like one of the diodes is bad. All were in the .5 range except one. Anybody know where to get this part other than CAT? Yes, I have searched the web with the part number

 

[Coaldust]

Easiest way would be to convert the Cat number to an Asin number, then go to EBay.

It’s probably a 204502447515 diode assembly. But, I would verify that. It may have a number on it.