Engine Block Heater Receptacle Not Working

[randyw]

Our coach is a 2005 MADP - 4030. In the electrical connection compartment, located on the driver’s side rear of the coach, is a receptacle labeled “Block Heater”. Inside the coach in the compartment above the passenger seating compartment is a switch labeled “Block Heater”. While connected to shore power I plugged the block heater plug into the receptacle and turned on the switch. A LED light above the switch lights, but nothing happens with the block heater. I checked and there is no power going to the receptacle (checked with a trouble light). I reset the 110v breaker in the bathroom labeled “Block Heater”, but still no power at the receptacle. I plugged the block heater directly, via extension cord, to 110v and it seems to work.

I’m wondering if there is a relay that the switch in the coach activates. If so does anyone know where this is located? Any other thoughts?

I know winter isn’t here yet, but I want to be ready for the trek south in November.

[Skip426]

I would suspect a bad switch , you can pull the switch, and test with an ohm meter when the coach is not plugged in ( gen set off of course).
Next would be the plug-in. Or you could start there. No relay in the system.
You can pick up a live circuit tester, for 110 v and tell if there is power at the plug-in. About $12 handy because it can help trace circuits in walls too.

[randyw]

Thanks Skip. So, the switch is running 110v? There is an electrical junction box not far from the receptacle to which the 110v wiring runs. In the box, besides the 110v wiring, are some smaller wires and what looks like a relay. Any idea what this is for?

[Skip426]

Not a clue , that's something my old coach doesn't have .
Can you post a picture?

EDIT: Could be a temp sensor , but I can't imagine why.

[hes4all]

I don't believe that the switch is 110. I think it is 12 volts and when on it activates a relay. I could be wrong amd most likely are?

I will look at my 06 MA for you tomorrow if you haven't got it working.

[danleininger]

Had this happen to me and while at Newmar I asked about it. The tech opened the panel above the drivers seat and simply replaced a wire that had fallen off the back of the switch.

Hopefully yours is that simple.

[randyw]

Will check that. Thanks.

[Skip426]

hes4all's; reply got me thinking, that maybe Newmar changed things over the years.
Does the switch, in your coach , look like a household lighting switch, with an indicator. Or is it a smaller rocker switch like the hot water control?

If it's similar to household then it should be a 110v circuit.
The old ; walks like a duck, quacks like a duck, must be a duck thing.

[randyw]

The switch is a small rocker switch that looks like the one for the HWT. That's why I was thinking it is 12v. Tonight I will have a better look inside the electrical junction box near the receptacle to see if there is in fact a relay in there. I'll also check to see if a wire has simply fallen off of the rocker switch. The LED above the rocker switch does come on when the switch is activated.

[allynne]

RandyW, rather than get guesses and opinions from this site, why not just call Newmar and ask them about power source and relays. One call should get you on the right track.

Al Sawyer
'05 Mt. Aire

[hes4all]

Originally Posted by Skip426

hes4all's; reply got me thinking, that maybe Newmar changed things over the years.
Does the switch, in your coach , look like a household lighting switch, with an indicator. Or is it a smaller rocker switch like the hot water control?

If it's similar to household then it should be a 110v circuit.
The old ; walks like a duck, quacks like a duck, must be a duck thing.

Skip, mine is the rocker switch. quack quack!

[Skip426]

Originally Posted by hes4all

Skip, mine is the rocker switch. quack quack!

And mine is household , type , hence my previous replies.
I wonder when they changed over and why?
Fewer things to go wrong with a strictly 110 circuit.

[randyw]

I won't get time to have a look at it until the weekend, but definitely a relay in the junction box. The white 110v wire is cut and goes into the relay and back out another connection. Will check to see that there is 110v power first and is so then the relay. Checked the wires on the back of the switch and all looked good.

[randyw]

So, spent time this morning digging into the engine block heater problem. Found that the relay in the outside compertment is working fine, but no 110v power to the relay. Tracked the issue back to the breaker panel in the bathroom. The 15 amp breaker is working fine and there is power going into the connection (5th connection from the left) at the circuit board in the picture, but no power at the 4th connection from the left where the circuit comes back out of the circuit board. We removed the two wires from the circuit board and by connecting them was able to get everything working. We didn't leave it that way as not sure of the purpose of the circuit board. Given the loop around the main ground wire (left side of the picture) it appears that the circuit board might protect the circuits in the event of power surges or dirty power. There are relays on the circuit board that probably open the circuit in the event of dirty power. Given the relays are attached to the circuit board this might cost me a new board.

Anyone got any ideas?

Skip, Jamie B was leading the diagnostic adventure this morning.