DC problems when furnace is on

[dhfenton]

Hi, my first post here. I believe I have an issue with 12V fluctuations when my furnace runs. I'm plugged into shore power with solar battery charging on my Wild Wood Heritage Glen 5th wheel. Battery charger says 13.4 V at the battery. Battery disconnect switch is positioned to connect the batteries to the converter.

What's happening is when the furnace is on at night I am getting E3 errors on my Dometic fridge , AND the blue knob lights around my Furrion stove go on and off, to varying degrees, by themselves. Sometimes all the way bright, and other time somewhere in between that and off. I've also had a motion activated pantry light come on when this is going on. Both the stove and fridge have 12V control circuitry, and the E3 error is a comm problem within the fridge.

I suspect my converter is bad, and is having enough voltage issues to cause control board problems; but, not enough to mess up the time display on my stereo. The reason I strongly suspect the converter is that I had a reverse polarity issue (we all know why) last fall and it was having voltage issues when not connected to the batteries. Connected to the batteries, it has worked fine until the last two days when we started using the furnace. I think because the furnace blower has such a large draw, it's exposing the converter issues.

Do you agree that it's time to replace the converter, or could it be something else?

[Dave Marchetti]

I would try to check all wiring connections from the converter to those accessories. I know my wiring had a lot of incredibly large wire nuts and I can see how easily a loose wire nut could cause problems. Some of my wire nuts needed retightenig. You may also have buss bars that you can check.

[dhfenton]

Originally Posted by Dave Marchetti

I would try to check all wiring connections from the converter to those accessories. I know my wiring had a lot of incredibly large wire nuts and I can see how easily a loose wire nut could cause problems. Some of my wire nuts needed retightenig. You may also have buss bars that you can check.

Thank you. I will check those things first.

[5picker]

Have you monitored converter voltage with a multimeter to see what the output is when the furnace kicks in? Assuming the converter is bad by monitoring a flickering stove illumination knob, the stereo display or what the thermostat display is reading, is just a guessing game.

Since you've admitted the converter had reverse polarity issues, one needs to do some diagnostic testing with a meter when the converter is under load.

[dhfenton]

Originally Posted by 5picker

Have you monitored converter voltage with a multimeter to see what the output is when the furnace kicks in? Assuming the converter is bad by monitoring a flickering stove illumination knob, the stereo display or what the thermostat display is reading, is just a guessing game.

Since you've admitted the converter had reverse polarity issues, one needs to do some diagnostic testing with a meter when the converter is under load.

I can do that too. My biggest reason for thinking the converter is the problem is that after I replaced the fuses following the “reverse polarity incident” the lights would dim when a load was put on and it wasn’t connected to the battery. The converter is pretty easy to get to in my rig, so I can turn the furnace on and test it.

[Bob K4TAX]

Originally Posted by dhfenton

Hi, my first post here. I believe I have an issue with 12V fluctuations when my furnace runs. I'm plugged into shore power with solar battery charging on my Wild Wood Heritage Glen 5th wheel. Battery charger says 13.4 V at the battery. Battery disconnect switch is positioned to connect the batteries to the converter.

What's happening is when the furnace is on at night I am getting E3 errors on my Dometic fridge , AND the blue knob lights around my Furrion stove go on and off, to varying degrees, by themselves. Sometimes all the way bright, and other time somewhere in between that and off. I've also had a motion activated pantry light come on when this is going on. Both the stove and fridge have 12V control circuitry, and the E3 error is a comm problem within the fridge.

I suspect my converter is bad, and is having enough voltage issues to cause control board problems; but, not enough to mess up the time display on my stereo. The reason I strongly suspect the converter is that I had a reverse polarity issue (we all know why) last fall and it was having voltage issues when not connected to the batteries. Connected to the batteries, it has worked fine until the last two days when we started using the furnace. I think because the furnace blower has such a large draw, it's exposing the converter issues.

Do you agree that it's time to replace the converter, or could it be something else?

Very well could be something else. Check the negative battery cable where it connects to the frame. I've found these are exposed to the weather, road grime, etc. and are poorly attached electrically.

Ours was attached by a single #10 or #12 self-drilling screw with no lock washer. The paint was never removed in that area. Needless to say when I found that, I removed the screw, drilled out the hole to 1/4", took my rotary tool, and removed about 1/2" of paint on both sides around the hole. I used a 1/4" stainless steel screw with internal tooth lock washers on both sides, then the freshly cleaned negative battery cable terminal, followed by a flat washer and nylon locking nut. Shoot the area with a bit of black paint if you are concerned about any rust. Do not add any grease or such as it will only accumulate road grime.

Bob

[Aussieguy]

agree with BOB to get a good negative to frame connection
BUT would not put any washer between cable lug and frame
DIRECT contact is best

Nylock nut or locktite can get hot and loosen...

Use a longer BOLT and put a standard nut to tighten the lug down correctly..... then a SECOND nut to act as a lock nut ...
Hold first nut with a wrench (spanner) as you tighten the locknut


Alternatively ....
put a standard nut nice and tight, then use a center punch to damage some of the thread.
Works best if you dimple just where the nut and bolts thread touching

RUN battery cable so it lays in a NATURAL position no tension on it

[Bob K4TAX]

Originally Posted by Aussieguy

agree with BOB to get a good negative to frame connection
BUT would not put any washer between cable lug and frame
DIRECT contact is best

Nylock nut or locktite can get hot and loosen...

Use a longer BOLT and put a standard nut to tighten the lug down correctly..... then a SECOND nut to act as a lock nut ...
Hold first nut with a wrench (spanner) as you tighten the locknut


Alternatively ....
put a standard nut nice and tight, then use a center punch to damage some of the thread.
Works best if you dimple just where the nut and bolts thread touching

RUN battery cable so it lays in a NATURAL position no tension on it

Ideas and concepts may differ.

Note that I stated to use "internal tooth lock washers". They are different than split lock washers and are different than external tooth lock washers. They are for different applications. The correct lock washer application assures the tightening of the nut will bite into the frame and the battery cable terminal. If the nut gets loose and heats, it wasn't tight enough to begin with or was not torqued to specs which is 94 ft/lbs.

Gotta do it correctly or it becomes a "science project with an unknown outcome".

Bob

[dhfenton]

I looked over some of the other potential causes suggested, and the problem still seemed to be the power converter. I replaced it since it’s a fairly cheap part, and the problems have stopped. Thank you all for your alternatives issues regarding this

[Aussieguy]

GM decided those star washers cause more problems than benefits
they issued a tech bulletin not to use them
All General Motors Passenger Cars, Trucks and Utilities Use of Star Washer on a Body or Chassis Ground - kw wire connector terminal starwasher star washer. GMC Truck GMC W-Series Commercial W5/W6/W7/W7HV 2003

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On my part ..... Not unknown or guesses.

before I "Fixed" the negative connection I was getting maximum 20 amps going to batteries ... measured using bluetooth on the battery

After the "fix" I measured 50amps from converter going into battery
again measured via bluetooth on battery
both times battery was discharged to 20%

you could leave the lower amp connection if you are mostly connected to shore power won't hurt the battery.
BUT if you want to use generator, fixing that connection and getting full amperage will save you a lot of gas and generator run time.

got mine all fixed up..... then stopped using converter for charging went to solar

so now all my 30amp power can be used by a/c and microwave , water heater etc ..
worked out the converter , would use about 6 -8 amps @ 120v charging a heavily discharge battery.

when you only got 30 amps to play with that's a good saving!

.