15 Amp parasitic draw

[michael7177]

15 Amp parasitic draw when the Refrigerator 20 Amp fuse is in. The parasitic draw only goes away when the fuse is pulled.
What could be causing this based on the tests below?

Monday, January 16, 2023
I got multiple errors on the microwave. I’ve noticed this perhaps on two previous occasions. I have to stop and clear the microwave and punch in the time again. Maybe it’s the generator?

Friday, April 7, 2023
The AC/DC power source to my fridge is not working when plugged into shore power at cousin Mark’s. A buzzing sound occurs emanating from the green dinosaur board.

Thursday, June 29, 2023
Two brand new batteries from Batteries Plus
SLI 31DT M AGM DC 2@ $289.99
12V 31DT DUR ULTRA AGM 30
EV31-115, SLI 31DT M AGM DC, SLI 31DT M AGM DCA

Full Warranty until 2025-12-29
Environmental Fee 2 @ $2.00
Install Basic 1 @ $25.00
Tax $44.95
TOTAL $653.93

Fridge still not staying lit.
Also a very serious electrical short


Thursday, July 6, 2023
Spoke with Joe at Dinosaur Electronics (541) 994 4344

Yes they still sell parts for the Dometic RM 3663. Replacing the Dinosaur Board can be done by myself.

Buzzing sound was probably a chattering relay. When using DC Power that’s a 30 amp draw and will crash weak batteries. My batteries were 10 years old. I accidentally left the RV in DC mode for 2 hours in early May. So I finally killed my coach batteries after taking good care of them for 10 years. That’s more than double their life expectancy.

Joe described what was happening with my refrigerator not staying lit. After 30 seconds the propane goes out. It’s probably the thermocouple. To test for this remove the green cover on the Dinosaur Board. Set your multimeter to 200 millivolts for this DC range.
Put the positive terminal on J3 and the negative terminal on J10. It should read about -25 millivolts. If not then it’s probably time to replace the thermocouple.

I did the test and spoke to to Joe again.
-33 millivolts was a good reading. 20 amp charger controller Fuse in. Coach Batteries IN USE.


Joe said the Dinosaur Board will work with -15 millivolts or better. He likes -25 mV but -33 mV is good too.

What caused the board to fail? AC ripple in DC supply caused by weak batteries. So when I was plugged into shore power or perhaps the generator running caused the AC ripple to blow out the microprocessor in the Dinosaur Board. This happens when the Coach Batteries are weak. Good batteries act big capacitors.

Contact RVShop.com Rocky 877-249-8571 to replace my P-711 Dinosaur Board.

Dinosaur Electronics are happy to offer free tech support on refrigerators, furnace and air conditioning.


Thursday, July 20, 2023
Repeated the test of LARGE AMP DRAW from refrigerator, ISOLATING FOR FRIDGE EYEBROW.
13.2 VOLTS / -00.6 AMPS**** / 99% FULL, Engine OFF, Coach Batteries set to OFF. Charger/Controller Breakers OFF. FRIDGE EYEBROW OFF, 20amp fuse IN.

COACH BATTERIES SET TO ON
13.0 VOLTS / -14.6 AMPS ****

EYEBROW TURNED ON AND SET TO AUTO-GAS but it shuts off after 30 to 60 seconds as expected, due to the problem described by Joe at Dinosaur Electronics. Still a 15.7 AMP DC DRAW even though the EYEBROW is set to Auto-Gas.

20 AMP REFRIGERATOR FUSE IS PULLED and -00.1 AMPS

[BobW9]

The 14.6A draw is the fridge on DC. It must be defaulting to that for some reason, probably the bad board.

Contrary to what many people think, the fridge does not pull 30 amps. The Dometic manual states it requires a 30 amp DC fuse, but that just means they want a fuse high enough to handle a surge without causing wear in the fuse. The normal power for a circuit should never be close to the rating of the fuse because that will wear out a fuse over time.

I did find somewhere on the web when searching a few years back, just one place that referenced the fridge as using about 15 amps on DC, but I think that might have been someone that measured it, not official Dometic docs (though it might have been a Dometic rep answering a question on a forum).

The distribution panels that came with the Chinooks are only rated for max 20 amp DC fuses, so using a fuse higher than that would void the warranty, and might be dangerous. Note the fuse you’re pulling to stop the draw from the fridge is 20 amps, and assuming you have the original panel (or look in the Concourse manual), Chinook labelled the fridge fuse as 20 amps, using an 8 gauge wire.

I find it interesting that Dometic would have their manual state a 30 amp fuse, given that there are only one or two distribution panels I could find that are rated for 30 amp DC fuses (I bought one of them, it uses slide-in Quick Connectors rather than screwing down bare wire, which appears to be why it can have higher current - it has 2 near-identical models, and the other model uses screws and is max rated 20 amp fuses). I bought it because I like the security of quick connects, as I am never confident with screw down connections. I have no fuses over 20 amps, as there is nothing I use, or even know of, that requires over 20 amps.

[Scott]

Chinook labelled the fridge fuse as 20 amps, using an 8 gauge wire.

Yours is 8awg? Nice. Mine was 12.

Although the connections on mine looked ok at the terminals, the +12 wire itself had black corrosion all the way back about 5 feet, at which point I abandoned it completely and ran new wire. I would look into the quality of all connections, but also check resistance and voltage drop along any associated wires trying to pull that kind of amperage. And I promise the grounds could warrant some attention if they're original.

This isn't necessarily going to solve this particular mystery, but water and moisture and heat in the lower fridge vent area is not a good combination for these connections. I've seen several wires on my rig with the black death corrosion, all of them outdoor connections. The trailer lights (tail lights) come to mind.

[michael7177]

Bob and Scott,
Thanks for responding. Bob mentions replace the board which seems like an easier first step to make than doing voltage tests and or reconditioning the wiring. I will call Dinosaur Electronics to ask them if it’s defaulting to DC because it’s been blown out.

Scott mentions corrosion.Here’s how it looks. I don’t know how to replace wiring, identify black corrosion, or do voltage tests. But I could watch some videos to learn.

[Scott]

Hi Michael,

Looking at your picture, I'd say that ground stud is not so great. There's a wire that is nearly disconnected. And the rest of it is certainly in need of a cleaning. That's a lot of connections for one stud; ideally they'd be on a bus.

Since I don't know what those connections are, I'm not going to say this will solve your problems, but it should be done regardless.

[michael7177]

Hi Scott, Glad you mentioned that. I was wondering what to do about it. I’ll research how to clean these connections and create a bus.
Also spoke with Chris at Dinosaur and he said to pull the 30 amp fuse to see if the 15 amp draw goes away. I wonder if replacing the board will fix the problem. That's another question I need to ask him.

Thanks!

[michael7177]

Wednesday, July 26, 2023
Scott made a very good insight which solved my problem!! Scott assumed that the failed Dinosaur Board P-711 was stuck energizing the DC Heater Element.

So I sought out how to test for this, even though Joe at Dinosaur Electronics said the board’s microprocessor has likely been fried due to plugging into AC while the Coach Batteries are low.

I'm investigating whether the Dinosaur Board is stuck in the ON position of energizing the DC element for the refrigerator. I'm going to try to isolate the circuits by:

1. Disconnecting the DC Element connector on the Dinosaur Board and take a reading using for amps with my Trimetric Battery monitor. I found the P-711 installation manual on their website and identified what all the connections are for. To fix the whole refrigerator problem I simply disconnected the J1 DC Element red wire. The results were that the -15 amp draw went down to the normal -00.4 amp draw. I turned the refrigerator on and it has been working well for 2 hours. So I haven’t bothered doing #2 below.

2. Disconnecting the 30 amp fuse on the Dinosaur Board and take a reading using for amps with my Trimetric Battery monitor.

Thursday, July 27, 2023
It’s been working great for 24 hours. So tomorrow I will call Chris or Joe at Dinosaur Electronics to explain what I’ve done, ask whether this is a safe operation or not, and follow their suggestions if it seems logical and not salesy.

Thursday, July 6, 2023
Joe said said strong Coach Batteries act as a big capacitor protecting the Dinosaur Board from AC power surges or as Joe called it, “AC Ripple”.

1. The propane shuts off after 30 seconds because the Dinosaur Board was likely fried due to and AC Ripple and my coach batteries being low. The coach batteries act as a big capacitor when plugged into AC power.

2. Testing the J3 and J10 connections with a multimeter showing ­33mV from the Thermocouple which means the Thermocouple is drawing power and is working properly. So it's the Dinosaur Board that is not working properly.

I was told I need to replace this Dinosaur Board based on the two things above.

[chin_k]

I don't know the board well, so it is just a guess here. It is likely that they use a relay to turn on the power to the DC heating element. With high current draw, sometimes the contacts get welded together, and stays on. You may want to use a ohm meter across the relay to see if it the case for you. If it is the case, you can simply replace the relay.

[michael7177]

How do I identify the relay?

[chin_k]

I see there is a Panasonic AJS1311F relay on the board, but I think it is for the AC heating element, since the specs says:

10 A 250 V AC (N.O.), 10 A 125 V AC,
6 A 277 V AC, 5 A 30 V DC

6A is too small for the DC heating element.

There are two EP1-B3G1S Kemet relays on the left side of your pics. They maybe the DC relays since the specs I found says:

Coil Voltage: 12 VDC
Relay Contact Form: 1 Form C (SPDT-NO, NC)
Contact Current Rating: 25 A

You should confirm it with the PCB manufacturer (Dinosaur Elec.) and see if they can tell you more than just pure guesses here.

One thing to do before playing with the relays is to unplug the DC heating element and see if the parasitic draw goes away. It should be pretty obvious if it is the one that draw the current, since it get HOT pretty quickly.

You should be able to measure the resistance of the contacts on the relays with the board removed from all the power. Measure the contacts that should be off ("N.O." or Normally Open) when the relay is unpowered, and if it is shorted, then you know the relay probably have welded contacts.


If you have to power up the board, keep in mind that the controller only need 12V DC to run, and you can unplug it from the AC outlet. If you are not familiar with electronic troubleshooting, it maybe better off to get a new controller board instead. I think getting 20+ years out of it is pretty good already.