'94 Charging System

[TomCat69]

I have been getting all sorts of different answers to this. Can someone give me the real deal. I have a 94' Mercury XRi Black Max 175 HP. Serial number is 0G000940. At idle, I get nothing on charging, hit the trim at idle and volts go down in the 11 volt range. At high rpm, this thing will charge at over 16 volts. I have just replaced battery with a good serviceable battery. Should I be getting some charge at idle or does this older system need to be cruising to get a charge. Also I understand I have 2 regulators. Could only one be bad. I understand that because a can get some charge, the stator should be ok. Thank you guys so much for the help. About to head to the marsh and I don't want any problems out there if you know what I mean.

 

[CharlieB]

Re: '94 Charging System

Unfortunate these charge very little at idle, voltage generation rises directly with RPM.

You can bench test those rectifiers disconnected with a volt/ohm meter... Often inspecting the backside potting a bad one will clearly show a burnt spot.

The biggest problem with these is poor connection to the stator yellow wires. Some Techs prefer to cut the bullet terminals off, twist and solder the wires and cover with heat shrink.

 

[TomCat69]

Re: '94 Charging System

I will pull them off and take a look. I did notice some discoloration on the yellow wires. Checked the ac voltage there and that looked good. The regulators are behind a plate so I cant see them. I did put a meter on the battery today. Looked like everything was ok. Idling around I had around 13 volts. Then later that day, my hummingbird depth finder started giving me a low voltage indicator when I started the motor. When I got home, I cranked the motor and checked the voltage again. Before I cranked the motor, voltage was low at like 11.8. I started the motor and voltage was at 12 and slowly started to creep a little. Got up to about 12.6-12.8. Gave it a little throttle and it came up to around 13. I may cut wires loose and solder. Got a big trip to LA coming up and I don't want any problems. Hell I may just go ahead and replace the regulators anyway. Seems to me they are kind of erratic.

 

[CharlieB]

Re: '94 Charging System

Have you priced those regs yet? If they pass bench tests and you improve the connections you may not have to pay the price to get new ones.

Once removed, Ohms test each yellow input to the red output. Depending on which meter lead is where you may or may not have continuity. Restest reversing the meter leads, continuity should be opposite from the last test. So you will have continuity only one direction from each yellow to red. None yellow to yellow.

Voltage generation is RPM dependent, very little at idle, increasing with RPM up to about 16 with a fully charged battery. The better the battery the lower the highest voltage as the battery itself is the voltage limiter.

The browned area of the yellow wires is an indication of the heat caused by high current flow thru a relatively poor connection for the amount of current. Thus the reason for many to solder those connections. Poor connections cause higher current flow, more heat, which in turn blows rectifiers/regulators. Prevention, as the old adage goes, an ounce can prevent pounds of problems.

 

[TomCat69]

Re: '94 Charging System

Regs are about 120 per unit. I had check the connections and all seemed to be ok. Looks like an intermittent problem. Sometimes I had good voltage at idle then later in the day i got an alarm on my depth finder of low voltage. I checked voltage again and was arount 11. Plus my tach is jumping around pretty often. Have seen that is a good indication regs are going bad. Battery is new, just bought it last week.

 

[CharlieB]

Re: '94 Charging System

A new battery can seriously tax a charging system as most new batteries are no where near fully charged and need a bit more than a couple of hours on a trickle charger to bring them up to full capacity.

The Merc manual clearly specifies 'a fully charged battery'.

Always charge any new battery before installation, in ANY vehicle, be it a boat, car, or lawn mower. It will save a charging system from over-heating and burning out a rectifier or an alternator.

 

[wired247]

Re: '94 Charging System

You are getting low charging at idle because the injection system uses a lot of current between the controller, the injectors and the high pressure pump . More current than your 40 amp stator is putting out at idle . Replacing the regulators wont change that. If you putt around at idle or anything under 2000 RPM or so a lot with an EFI equipped Merc V6 you will discharge the battery.