Merc 135 OB Voltage Regulator

[ajtait]

I've been having problems with my battery draining while the boat is not in use. I read about testing by taking the positive leads off the battery and using a voltage regulator to test between positive battery post and each positive lead. If any voltage is detected, a leak is present. I carried out this test and after some searching found it to be caused by the "red" lead on my voltage regulator. Once I removed this lead, I no longer had a reading on my meter. The voltage regulator has two leads attached, a "red" and a "yellow". The yellow had no affect on this reading (attached/or not)<br /><br />Does this indicate a bad voltage regulator and the likely source of my slow battery leak?<br /><br />Thanks in advance<br /><br />Allen

 

[wrenchtrnr72]

Re: Merc 135 OB Voltage Regulator

it could be volt. reg, or ign switch. you can also use a test light hook the ground clamp to the pos(+) post and touch each wire going to it(make sure it is disconected from battery). this is called checking for a draw, the easy way.

 

[dilligafda]

Re: Merc 135 OB Voltage Regulator

The amp draw from the regulator is measured in milliamps (VERY small amounts) and should only discharge the battery after an extended period of time. Start by eliminating the boat as the problem. disconnect everything but the engine and let it sit for the amount of time it takes to discharge the battery. If the discharge condition remains, then get a meter that will read milliamps and test the draw. It shold be below 500 milliamps. If it is higher, replace the regulator. Good luck and keep us posted.

 

[ronmold]

Re: Merc 135 OB Voltage Regulator

Have you tested the voltage when the engine is running especially at higher RPM's? This would be a good test for the regulator. The older merc regulator works by shorting the yellow lead to ground when voltage reaches a certain level, about 14V. This heats up the regulator and the stater windings and often fail. A voltage meter used to check for drain will not work as well as an amp/milliamp meter the way you first checked because of high sensitivity of the newer meters. How old is the motor?

 

[ajtait]

Re: Merc 135 OB Voltage Regulator

Thanks to all for your input! The motor is an 89 merc 135. The regulator looks like the rectifier but has two posts instead of three. ($150, yikes!) I'm going to take your advice and perform the tests desrcibe in my manual for the regulator. Test initial volatage then start and test again. I'll post results.<br /><br />Thanks again!<br /><br />Allen

 

[ajtait]

Re: Merc 135 OB Voltage Regulator

I executed a three step voltage test today. First, the voltage at the battery, motor not started, was 12 volts. Then started the motor, RPM at 2000, and checked it again. This read a shade higher than 13 volts. Finally, while it was running at 2000 rpm, I turned on radio, bilge pump, lights, and checked again. This was a little over 13 volts also. <br /><br />Does this indicate the system is charging properly? (and that the voltage regulator is working properly?)<br /><br />Next, I'll try leaving just the engine lead connected to the battery.<br /><br />Thanks<br /><br />Allen

 

[sledhead041]

Re: Merc 135 OB Voltage Regulator

If you know you have a drain on your system and you disconnected the rectifier and then the draw went away…..you found your problem. It doesn’t matter if it is giving the battery output it still can have a drain. You figured out your problem all by your self bud.

 

[KCLOST]

Re: Merc 135 OB Voltage Regulator

You have an "OK" charging system, but that doesn't prove that the regulator has a drain. If I were you I'd remove the regulator and see if the drain remains after storage for a while... Your previous tests may be correct, but I'd like to take the suspect problem out of the equation to make sure.<br /><br />That's most likely where the drain originates from, but just disconnect it to make sure.. Be careful running the engine without it though... I don't want you to fry anything... Just remove it after the battery is at 12-13 volts, and see if it drains like in the past....<br /><br />Good luck, and let us know...

 

[KCLOST]

Re: Merc 135 OB Voltage Regulator

I also wanted to mention, that you haven't proved to us that the battery is good! Are you charging it regularly to get it up to the 12V? I'd take it to NAPA or somewhere and have it tested just to make sure...

 

[ajtait]

Re: Merc 135 OB Voltage Regulator

The battery was new last fall, hardly used since.<br /><br />Need more advice on this. So earlier I mentioned testing the voltage output. With nothing on and engine not running, the battery measured about 12 volts. Then while the engine was running at 2000 rpm, the meter read a touch over 13 volts at the battery. So I guess the charging system is putting out 1 volt or so. <br /><br />I let the boat sit all week, with all cables attatched to battery. It started fine and had plenty of juice this weekend.<br /><br />BUT, while riding around the lake, the battery slowly lost it's charge. After a few hours, it wouldn't start up again. <br /><br />Is that 1 volt while charging enough?<br /><br />Would this be a regulator problem? Rectifier? <br /><br />Thanks in advance for your help<br /><br />Allen

 

[ajtait]

Re: Merc 135 OB Voltage Regulator

Can anyone help out?

 

[Barnacle_Bill]

Re: Merc 135 OB Voltage Regulator

MNMarineman gave you your answer. Change the rectifier. I'm sure if you test it with an ohm meter you will find a shorted diode. That would cause a drain and cause the recifier not to put out enough current for the regulator to regulate.<br />It doesn't take much to blow them.