Following Information Is Credited to and Posted with Permission of Doug Hampton of PMMI

Following information is credited to and posted with permission of Doug Hampton of PMMI Electronics with slight editing by Harry Saddock:

Bluebird GFI Trip Solution:

The problem arises because GFI protection modules trip if they sense an imbalance in the two legs of a circuit. An imbalance usually means that some electrical current is leaking and returning to ground through some unintended path. Thus, a fault to ground. I cannot remember the spec for sure, but GFIs will usually trip on an imbalance of from 5 to 15 milliamps.

In order to detect mis-wired or missing ground connections, the reverse polarity detector module allows some current to leak to ground to provide current to light an appropriate indicator LED. This was fine until GFIs came along. But since each of the LEDs in the original units drew a couple of milliamps each, and the total might be 8 to ten milliamps, GFIs would be caused to trip even with normal operation.

There being several models and configurations of reverse polarity indicators, I cannot tell you exactly what to do without seeing the unit(s). Some have 2 LEDs, some have four. Some are housed in conjunction with an AC voltage monitor, some are isolated. Some coaches have both. Some coaches have two different reverse polarity indicators (one inside, one outside).

But I would be glad to tell you, in general, what needs to be done, and then you can decide whether you still want to do the work.

The fix involves replacing the current-limiting resistors for each LED so the current is reduced to be under the trip point. In addition, since less current means less brightness for the LED, we replace the LEDs on the board with a 'low current' type to gain the brightness back.

My notes tell me that you will need to change out any 68K ohm 1/2W resistors that function as LED current limiters (should be all of them on the reverse polarity PCBs) to 130K ohm 1/2W 5%. The LEDs should change to the following types: red is HLMP-1700; yellow is HLMP-1719 (we change the green to yellow to show us the modification has been done).

WARNING: YOU SHOULD NOT ATTEMPT REPAIRS ON THESE OR OTHER ELECTRICAL DEVICES UNLESS YOU ARE FAMILIAR WITH ELECTRICITY AND THE SAFEGUARDS REQUIRED TO WORK ON ELECTRICAL DEVICES. WORKING ON THE AFOREMENTIONED ELECTRICAL DEVICES CAN BE HARMFUL OR FATAL. HIGH VOLTAGE IS PRESENT. IF YOU ARE NOT COMFORATBLE WORKING ON ELECTRICAL DEVICES, YOU SHOULD HAVE A CERTIFIED ELECTRICIAN DO THE WORK.

OK, I had to include the above just to cover my responsibilities. Please don't take offense.

You can get the resistors and LEDs from many different supply houses or catalog (and on-line) sources. I use Allied Electronics, Digikey and Newark, among others.

I can certainly make you up a kit with the number of parts you need (and maybe a couple spares). I need to know how many you need, but the kit would probably run $5 to $8.

Hope this helps.

Doug Hampton

______PMMI Electronics 281-293-8000 voice 281-293-8005 fax

Follow-up information:

Feel free to post any information to the forum! Hope it can help.

Regarding the soldering: It is possible to damage the board while removing components. But the main trick is to heat the solder at the component up fully BEFORE pulling on the component. I have ripped a few traces myself by pulling too fast. Depending on the type of soldering iron you have, this might take a split second or 2 to 3 seconds (20 to 30 watts of power should be plenty). The good news is even if the board is damaged, you can fix it without too much trouble by re-soldering or remaking the broken connections with some very thin wire or a resistor lead. Then the trick is to make note of the area you're working on beforehand so that if a trace does come off, you know where it was supposed to go. These boards are pretty simple, so you shouldn't have much of a problem.

One thing I forgot to mention about the LEDs: they are polarized, with 2 leads, and you must get the leads in the correct hole. If they are in backwards, they will not light. The LEDs normally come with one leg longer than the other, and the longer leg (the anode) must be connected to the cathode side (the side with the band on its end) of the 'blocking' diodes (1N4004 or 1N4007, etc.) in each of their circuits. This sounds harder than it is. Just study the circuit paths. If you get the diodes in and they don't light, try reversing them. There is another way to tell which way to put in the LEDs, and that is to look thru the old ones on the board before you take them out and note the internal configuration (a magnifying glass is helpful here), and then just match the direction of the internals for the new LEDs with the old.