Voltage Runaway

For issues involving the NS2 regulator.

Voltage Runaway

Postby JimWilcox on Mon Sep 20, 2010 12:41 pm


I have just wired in my new NS2 regulator, and I'm getting an error code that I have a Voltage runaway condition. Since this unit is brand new, could there be a problem with it? I am just in the process of replacing my old Next Step that had served faithfully for years, and therefore did have all of the correct wires in the harness to install this new piece. I also have an Eliminator that I had left in the system as it was fine. I have been down for many weeks while I have gone from one end of the system to the other (checked the alternator, checked for shorts with an ohm meter, checked the oil pressure switch, read through many posts in this forum, etc.) the only possibility for my failure was the Next Step. Now I have this error in the new piece. I haven't even turned over the engine yet (as I didn't want to cause any damage). I can tell you that I do have the flashing green LED signifying that I havent powered the on/off switch. I can also tell you the values of the vires with the system off... they are as follows:
pin 1 - 12.46 volts
pin 2 - 0
pin 3 - 0
pin 4 - 12.46 volts
pin 5 - 0
pin 6 - 2.94 volts
pin 7 - 0
pin 8 - 0

I also tested the TB2 side (although I dont have anything hooked in)

pin 1 - 0
pin 2 - 12.46 volts
pin 3 through 8 - 0

When I understood that the error message involved a voltage overage, I also tried to eliminate my bank 1 (starter bank) by disconnecting the cables - to no avail. My house bank which is composed of Trojan T-105's in series is brand new. I did set the Absorption voltage at 14.8 volts, the Float Voltage at 13.2 volts, and the Absorption time at 120 minutes (as per a call to Trojan Tech Support).

Can you advise what to do??

Jim Wilcox
Posts: 3
Joined: Mon Sep 20, 2010 11:44 am

Re: Voltage Runaway

Postby ruth on Mon Sep 20, 2010 4:54 pm

jim, tech says we need to send you another reg. Called, but no answer, left a message. Will try again tomorrow. Thanks.
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Joined: Sat Jun 06, 2009 6:04 pm

Re: Voltage Runaway

Postby JimWilcox on Mon Sep 27, 2010 8:53 am

Hi Ruth,

Thank you for sending out the new regulator. Unfortunately, it showed the exact same behavior as the first one. Here is a synopsis of what I have been seeing and what I have done so far to try to isolate the problem.

When I hook up the regulator according to documentation provided -- ground wire to the negative battery post is always attached first (my on/off is attached to an oil pressure switch, so the regulator is off, until I kick the engine over), once I attach the B+ connector, the Red LED comes on for a few seconds and then goes off. Then the Green LED comes on and is flashing for 3 seconds on/3 seconds off as expected. After another 15 seconds or so, the Red LED then starts flashing with the Voltage Runaway code (6 seconds on and 3 seconds off). When testing with the meter, B+ and Bat Volts both match and are equal to battery voltage. The absorption voltage, float point, and absorption time are set to the battery manufacturer's spec. (14.8, 13.2, and 120 minutes respectively). When I turn on the engine, the oil pressure switch turns on the regulator, the Green Field LED comes on, the Green LED indicator flashes the appropriate sequence for bulk charge and in a couple of seconds (all as expected), the 8 amp fuse on the B+ line blows. With the regulator off, I am getting a resistance of right around 3 ohms (2.8) across the field and Alt Ground pins which should be comfortably above the 1.2 you specify as minimum in the trouble shooting manual.

When attempting to debug the issue, one of the things I tried was to drop the absorption and float voltages down to a point where hopefully the regulator would feel the batteries were already at a full charge. When I did that, the system would come up and run normally and the fuse did not blow (most likely because the regulator wasn't pushing any current out to the field on the alternator). The other interesting thing that I noticed is that once the regulator turned on, the Red LED indicator stopped flashing the Voltage Runaway error.

I eventually got to the point where I wired up as simple a system as possible for testing/debugging purposes. I removed all the components from the boats electronics and wired the battery, regulator, and alternator together with a manual switch from the positive terminal on the battery to the regulator for the On/Off switch. At this point, the test system was wired exactly as the documentation shows with absolutely nothing else in the system.

It was wired as follows: 1 twelve volt battery. The positive terminal on the battery is connected to the positive post on the alternator, B+ on the regulator with an 8 amp fuse, Bat Volts on the regulator with a 3 amp fuse, and the On/Off on the regulator with a manual switch in-line. The temperature sensor was not connected to the regulator (I left it off since it was listed as optional and I was going for as simple a system as possible). The negative terminal on the battery was attached to Ground on the Regulator and the Ground on the Alternator. The ground on the alternator was attached to the Alt Gnd. pin on the regulator and the Field pin on the regulator was attached to the field on the alternator.

Once I attached the B+ with the switch set so the regulator is still off, I had the exact same behavior as described above. I double checked the voltages at all the pins on the regulator and got what I expected (battery voltage on B+, Bat Volts and nothing on all other pins) and I was still seeing the voltage runaway indication on the Red LED. I then turned on the switch to check the voltages in the regulator on but engine off mode. I saw the change in indicator lights where the Green LED switched from flashing the code for off to the code for Bulk Charge. The Red LED stopped flashing the Voltage Runaway error and before I could measure any voltages, the 8 amp fuse on B+ blew again. I stopped at this point and never even tried to start up the engine.

I have taken the alternator in for a quick bench test and it got a supposedly clean bill of health. At this point I am not sure where the problem lies -- I have simplified the system to where it only had the battery (new), regulator, and alternator in it and I was still blowing the 8 amp fuse when the regulator was on.

As far as the regulator goes, I have three main questions. First, why am I getting the Voltage Runaway error when I first connect the B+ (that is usually the last connection I am making since I have been replacing the 8 amp fuse on a regular basis) and why does it go away once the regulator is sees a positive voltage on the On/Off switch? Second, does the regulator have anything in its circuits that is supposed to monitor and shut down the current to the field pin if it gets to high, or will the regulator just keep pushing as much current through as it thinks is needed? And finally, is there anything involved in connecter/operating the regulator that I have missed or am doing wrong?

Additionally, I did note that the replacement regulator had a serial number only 1 removed from the original piece. Is there any chance on a faulty component for that production run?

I haven't shipped the original regulator back to you yet as I wasn't certain whether you would want me to hold on to it for comparison purposes during this debug.


Jim Wilcox

Thank you,

Posts: 3
Joined: Mon Sep 20, 2010 11:44 am

Re: Voltage Runaway

Postby Coulomb on Mon Sep 27, 2010 3:05 pm

All units are 100% tested here, so it's not likely that a production
error is causing the problem.

Let's isolate the reason for blowing fuses. Remove the B+ wire from the
regulator. Also remove the field wire from the regulator. With the 8A
fuse installed, connect the B+ wire to the field wire. If you have an
ammeter, better yet. Connect it in series with the two wire to measure
current from B+ to the field.

If the fuse blows, or you measure greater than 8 Amps, then the problem
is in the wiring or alternator.

We're still looking at the red LED issue.
Site Admin
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Re: Voltage Runaway

Postby JimWilcox on Tue Sep 28, 2010 10:46 am

Thank you for the feedback. I haven't tried the fuse test yet as I have the alternator off the engine. I am going to have it re-checked by another source. I'll post back with the results.

Jim Wilcox
Posts: 3
Joined: Mon Sep 20, 2010 11:44 am

Re: Voltage Runaway

Postby gfab on Sat Jun 04, 2011 4:23 am

Posts: 3
Joined: Fri Jun 03, 2011 11:45 am

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