Join Date: Jan 2003
Location: Maine Coast
Thanked 213 Times in 162 Posts
Rep Power: 16
I am trying to replace the alternator on my qm20 yanmar ...it was missing when i got the boat, so i dont know how it was wired....
here is what i can tell so far...it has three wires at the location,a heavy black that goes to motor bolt for ground. a heavy red that is battery positive. a yellow small gauge wire with a red stripe...maybe the tach trigger as far as i can tell.....
plus ...nearby is also a red wire w/black stripe small gauge with a disconnect connector ....the second part is missing....but it does have 12 volts with the key on......i am thinking this is the idiot light wire ...but the light doesnt appear to work.....
next ....the new alternator ( came with the boat) is a 105 amp, it has a four wire plug connector, i was able to buy a new pig tail to fit it.
the wires are labled as follows....left to right.....P ...tach ? next is ..L ...idiot lamp ?.....next is F with what looks to be an I above it....this one i have no clue ......and focus of my problem....is it simply not needed? .....or is it an ignition lead ? or is the F for field or something else?the last wire is battery pos....it goes back to the main positive post on the alternator...
the regulator is internal ,if that matters any.....does anyone have a wiring diagram or know how these are wired....i dont want to fry the alternator by wiring it wrong ( i have done that before)..not a pretty sight to have smoke comming from a brand new ( and expensive ) part.....
I hope this is enough information , its all i can come up with.....thanks in advance....... Ron
Yanmar / Hitachi alts often have the following wiring terminals but some had internal regulators and some external and some had different terminal designations. An alternator model # would really help..
This is what an LR155-4 has:
B = Battery +
E = Battery -
R = Tach
L = Charge Lamp
An LR-135-31 lacks the R terminal.
-Maine Sail / CS-36T
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