Another Alternator Issue

[Paddy]

I purchased a rebuilt alternator about a year ago for my 6LP and decided to install it last weekend. Replaced the alternator and belts, all good. Idle is around 13.2V and high rpms sits at a nice 14.5-14.6V, read on the gauge, garmin, cigarette lighter meter and at the alternator post.

Problem is when using the forward or aft bilge, the voltage jumps quickly to 15.7 to 16.1 and then settles right back down to 14.5. Again, quick jump and then the pumps run at 14.5. The aft pump did not sound healthy so I also went ahead and replaced it with another 2200GPH Johnson. I cut all wires back for clean connections and even replaced many of the 8 gauge grounds that had eroded connections. Voltage jump is still there.

Full disclosure, I am not 100% sure if I had this issue with the previous alternator but I doubt it as the jump is so noticeable. Nothing wrong with the previous alternator, just decided to change it as its the original one from 2004.

I can't replicate the jump with any other accessory.

Thoughts?

[catalina_mike]

Check you grounds from the batteries to the engine block also. Not just the bonding grounds.

[Paddy]

Batteries to ground were cleaned prior to launch. I sent an email to the rebuilder too. Might have the OEM rebuilt just for the heck of it to see if it goes away. Very strange and annoying.

[dkirsop]

Sounds to me that what you are seeing is the initial in-rush current as the pump comes up to speed. Once the pump is at operating RPM then the current draw reduces to normal. You may not have seen it before due to corrosion at the wire connections but now that you have cleaned them up there is less resistance in the system.

[Paddy]

Bum rebuilt alternator. It definitely jumped all over when I hit the bilge pump but this weekend it also wandered between 14.5V and 17.0V while cruising and even when revved in neutral. Put the OEM back on and all is good. The OEM has 1500 hours on it so I'd rather keep that as a backup.

Bought it over a year ago so I am out of luck there, ordered another one today.

[Serenity]

I decided to replace my alternator due to fluctuating circumstances. I checked with the local rebuild guy, and he anted $135. I went on line and found prices ranged from $90.79, $90.81 and $181.67. I went with the $90.79 and received the alternator in 3 days. Interesting, Yanmar is Toyota and the alternator was made in China. The alternator was a dead equal to the one that came off the engine. The biggest headache was getting the old one off. Perhaps the best way would be to back out the lower bolt and remove the top bolt when you are ready to remove the unit. The lower bolt is very snug up against the wooded backboard against the fuel tank.