Alternator

[Tim75]

Hello to all.
I have some issues with battery charging from alternator.

Engine is Merc 2001, round engine cover, under flywheel alternator.
There are 2 sets of charging coils and 2 voltage reg's. At 2000 RPM, the upper VR gets too hot to touch after 5 minutes. The lower VR temp barely above ambient. Max voltage @ 2000 rpm is 13.2. Both VRs are in fact connected to battery at solenoid.

1) Is that much temp rise normal?

2) Thru process of elimination, it seems the lower VR is dead even though tach still works. Do these units commonly fail?

3) Are after-market units worth the $? (sierra brand) Merc OEM is $170.

Thanks in advance. Tim75

 

[Dr Honda]

They get warm when working. If you want to know exactly what they are doing... lift the red wire, and put a meter on it. You should have voltage.

I wouldn't list the VR failing as a common issue... but they do eventually fail. Personally... unless the aftermarket units are VERY cheap... I tend to stay away from them. They are normally made in China, and the quality can be questionable.


As far as the one VR running very hot... it could be from a battery that is ready to be dead. I know some people try to limp a bad battery along for longer than they should... and in turn... it's VERY hard on the charging system... and low voltage is also bad for the starter. I'm not saying you have a bad battery... but it's a possibility, or a previous owner could have.

 

[Tim75]

They get warm when working. If you want to know exactly what they are doing... lift the red wire, and put a meter on it. You should have voltage.

I wouldn't list the VR failing as a common issue... but they do eventually fail. Personally... unless the aftermarket units are VERY cheap... I tend to stay away from them. They are normally made in China, and the quality can be questionable.


As far as the one VR running very hot... it could be from a battery that is ready to be dead. I know some people try to limp a bad battery along for longer than they should... and in turn... it's VERY hard on the charging system... and low voltage is also bad for the starter. I'm not saying you have a bad battery... but it's a possibility, or a previous owner could have.

Thanks for the near-instant response.

I am afraid I have 1 bad VR and a bad battery. Need some O/T at work.

Service book mentions 15A and 40A alternators. How do I know which I have?

Thanks

 

[Dr Honda]

Since you said that you have 2 regulators... I'll assume you have a 240. Basically the EFI and Di engines have a 40a. Carb engines have a 15/20a.