Balmar ARS-5 Voltage Regulator Power Source

[Mike McDonald]

I have an M25XP engine with a Balmar ARS-5 voltage regulator. I upgraded from a failed ARS-4 in 2014. It is mounted outside of the engine compartment to avoid overheating (under the head sink space). The regulator suddenly stopped working. I went through the troubleshooting steps in the manual and then called balmar tech support with the voltage readings. This indicated that the regulator is not receiving power. The regulator harness brown wire for power is connected to the engine oil pressure switch circuit. I'm not sure how this circuit is supposed to work. I know that it is supposed to turn on the warning light at the panel in the cockpit when oil pressure is low, such as momentarily when starting the engine. The light does blink on when starting the engine. I don't seem to be able to get a voltage reading for that circuit when the engine is running. It should read the battery voltage. Any ideas would be appreciated.
Mike....

[Stu Jackson]

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1.
This indicated that the regulator is not receiving power. The regulator harness brown wire for power is connected to the engine oil pressure switch circuit. I'm not sure how this circuit is supposed to work.


2.
I know that it is supposed to turn on the warning light at the panel in the cockpit when oil pressure is low, such as momentarily when starting the engine. The light does blink on when starting the engine. I don't seem to be able to get a voltage reading for that circuit when the engine is running. It should read the battery voltage. Any ideas would be appreciated.
Mike....

Mike,

1.
The regulator power should be coming from the ignition switch, not the oil pressure switch circuit, because that circuit only gets energized after the engine starts.

When I replaced my OEM alternator I installed an MC-612, and drew detailed wiring diagrams.  These are in the Electrical Systems 101.

Alternator Regulator Wiring Diagrams - all three http://c34.org/bbs/index.php/topic,4548.0.html

Also, the Critical Upgrades topic discusses the unforeseen consequences of the M25XP and M35 engine wiring changes related to the oil pressure switch and the the operation of the electric fuel pump.  I only mention this so if you don't already know about it, you can find out.

2.
Perhaps your oil pressure switch is faulty.  In most cases, IIRC, it's not the switch but the wiring connections.  Ken Kloeber has written a lot about this.  Since I don't have experience with it because I have a simpler M25, I'll leave this one to others.

[Ron Hill]

Mike : Like Stu said the KEY switch.  Just make sure you wire it to the continuous pole and not the intermittent pole!! 
In the M25XP engine the oil pressure switch is powered when the key switch is ON (as an alternate)!  The regulator power is best to the key switch!!

A thought

[Stu Jackson]

Mike : Like Stu said the KEY switch.  Just make sure you wire it to the continuous pole and not the intermittent pole!!

A thought

Mike,

WAIT!

Just to be clear, the regulator doesn't need to be ON all the time.  You WANT it to go off when you turn the key off.

So, use the correct pole on the key switch.  Sometimes terminology can be confusing...

[Ron Hill]

Mike : Clear as mud?  The ON pole is the first detent and the Spring Loaded (intermittent) pole is the far detent for the key!! 
Like Stu said if the key switch is OFF, then the ARS and any other accessory on that pole is also OFF.

A thought   

[Stu Jackson]

That's clear now.

FWIW, when I replaced my key switch a couple of years ago, I found a 3 position switch there, although my boat only used two because I have both pushbuttons for glow plugs and start.  The factory only wired two poles anyway!  I just put a two position I/O in instead.

[Mike McDonald]

Stu & Ron,
Thanks for the information. I'm going back to the boat tomorrow. Hopefully I can sort this out based on your recommendations. I appreciate the help.
Mike.....

[KWKloeber]

Mike and Stu,

Mike, what is the "brown" wire for, nominal 12v power to the Balmer?

I don't see any way your Balmar is "connected to" the oil pressure switch, and ever worked. 
There is no 12v power to the oil switch on the XP (and M-25 - Stu the oil pressure circuits and switch are identical on the 25 and XP **.) 

The 12v power goes to the ALARM, the (blue) harness wire to the oil pressure switch is a GROUND wire, that completes contact with the battery negative (hopefully, thru the engine) when the pressure goes < ~5-7 psi.  Above 5-7 psi there is no ground connection to the blue wire.

If the BROWN wire is for 12v power to the Balmar, it may be connected to the alternator FIELD EXCITE (purple) harness wire, which is powered when the key switch is in the "I" (a/k/a, "on", "run", or "ignition") position (the "I" terminal on the switch, opposed to the spring-loaded "S" (sometimes used for "start", sometimes "preheat", sometimes just dead, sometimes there's only a 2-position switch) terminal, if you have a 3-position switch.)

-ken

** the oil switch circuit is the same on the 25, 35, and XP, and should never see a full 12v -- the oil switch only completes a ground path from the alarm "S" - "switch" (ground) terminal.  +12v power goes to the "+" terminal of the alarm. 
The change to the 2-wire oil pressure switch and the revised circuit was made starting w/ the "A" engines and of course is on the "B" engines.

[Mike McDonald]

Thanks guys! I connected the regular brown wire to the ignition switch wire and it seems to be working fine now.
Bob, I don't understand how it worked in the oil pressure switch circuit for several years either?? The Balmar troubleshooting guide does show that as an option and that was how the previous ARS-4 was wired when I bought the boat as well. The ignition circuit makes much more sense to me, and now it works.

Thanks to all!
Mike......

[Ron Hill]

Mike : When you turn ON the key switch of the M25XP engine the oil pressure is activated ON.  You just might have had a bad connection? 
However the regulator power is best from the key switch!

A few thoughts    

[KWKloeber]

Ron - With the key on or off, the oil pressure sw is connected to GROUND (thru the switch) it is not supplied 12 volts.

Mike - the only way I could see the reg working that way is if you had a BAD oil alarm, and the faulty alarm passed a full 12 volts to the ground (S) terminal on the alarm -- so when there was oil pressure, the switch would be open, so the wire to the switch would have 12v. 
With no oil pressure, the oil switch would be closed and so would dead short the circuit to the engine ground (and the reg would see near zero volts.)

[Ron Hill]

Ken : Guess you are right. 
The oil pressure registers with only a - (negative) wire.  No +(positive) necessary!

A New Thought

[mainesail]

Ron - With the key on or off, the oil pressure sw is connected to GROUND (thru the switch) it is not supplied 12 volts.

Mike - the only way I could see the reg working that way is if you had a BAD oil alarm, and the faulty alarm passed a full 12 volts to the ground (S) terminal on the alarm -- so when there was oil pressure, the switch would be open, so the wire to the switch would have 12v. 
With no oil pressure, the oil switch would be closed and so would dead short the circuit to the engine ground (and the reg would see near zero volts.)

You can also tie the neg of the regulator through that ground circuit so the reg can't boot until there is oil pressure. Not the best idea, because regulator B- is part of the volt sense circuit, and oil pressure switches can "chatter" a bit at low RPM/low pressure, which is not good for the reg, but some folks do it. With the programmable delays in the Balmar regulator there is no need to have it powered through the oil pressure circuit.