Attwood WH switch causing 15 amp fuse to blow

wolfe10 wrote:
Hope you have a fuse at the battery end of that wire! And, if you measure reasonable amperage, you know you have a wiring issue, not water heater issue.

While running a new wire may not be any fun, it will sure be less $$$ than a new water heater or major component.

I thought I had it working it started fine and I took a walk around the campground and when I came back it was off. Thinking it came up to temperature and shut off I took a shower and it was only luke warm. So something else is wrong also. It would not go back on even when the hot wire was disconnect and reconnected.

Hope you have a fuse at the battery end of that wire! And, if you measure reasonable amperage, you know you have a wiring issue, not water heater issue.

While running a new wire may not be any fun, it will sure be less $$$ than a new water heater or major component.

I tried running a long wire from the battery to the thermal fuse in the WH and it work so at least we can have hot showers. I am still trying to figure out a more permanent fix.

wolfe10 wrote:
Rather than trying to find the problem with the hot wire from switch to water heater, just pull a new one. After disconnecting the old wire from the switch, check with a voltmeter to verify that it is indeed disconnected and leaving it in place will cause no harm.

Thanks, that would be the easiest if I could just see a way to run the wire without it showing. It has to go from the left side to the right side. Right now it runs from the hood in back of the MW inside the wall and I think under the MH to the WH.

Rather than trying to find the problem with the hot wire from switch to water heater, just pull a new one. After disconnecting the old wire from the switch, check with a voltmeter to verify that it is indeed disconnected and leaving it in place will cause no harm.

I wanted to thank everyone for their help in trying to diagnose this problem it is much harder when you are traveling on the road and you have to do all the driving and can only work on this problem at rest stops. Doug I did check the board and it was bad. I have the potted board and according to the manual there should be continuity between brown wire track and green wire track, I showed open. Same with the lamp track test and valve track test. Also with the board disconnected I connected the brown wire to the gas valve wire with the wall switch on and it blew the fuse again. So it sounds like that wire from the switch to the board is grounded somewhere but I can't see where it's grounded. I can get my head in the compartment and see the three wires going to the top of the water heater two are white and one is brown I tried moving those and following them but I cannot see where they go beyond the top of the fuel tank. Is there an easy way to get the WH working again until I can find this short? Also could this short have caused the board to go bad? I can't see how but this problem happened suddenly.

Gjac wrote:

wildmanbaker wrote:
OK, if you have fixed a loose wire on the HW switch, then remove it find the hot feed by using your meter on the 12V setting by checking each wire to ground for power. When you find the hot feed, disconnect the other wire from the switch, and the other end of the wire from the HW heater control board. With the meter in the OHM setting, check the wire you disconnected from the switch, between the connector and ground. If it reads "0" ohms the wire is not shorted, and the problem may be in the control circuit somewhere.

. If I understood your post, I took the terminal with no voltage to ground disconnected it and read continuity to the metal hood range cover with the muti pin plug disconnected from the control board. More specifically I read 1.4 ohms with the leads shorted out and 5.6 ohms when checked as described. I know attwood has on their web site how to check the control board with an ohm meter which I will do tomorrow.

Since the SHORT stayed when you disconnected the control board, WHY would you think you need to test the control board? You do not. The Short is between the casing of the Water Heater and the control switch inside. On MOST Atwood installs, you have to PULL the water heater out about 8 inches to verify the 4 wires that connect to the water heater wire bundle. Very few RV's have inside access to the top of the water heater. Doug

wildmanbaker wrote:
OK, if you have fixed a loose wire on the HW switch, then remove it find the hot feed by using your meter on the 12V setting by checking each wire to ground for power. When you find the hot feed, disconnect the other wire from the switch, and the other end of the wire from the HW heater control board. With the meter in the OHM setting, check the wire you disconnected from the switch, between the connector and ground. If it reads "0" ohms the wire is not shorted, and the problem may be in the control circuit somewhere.

. If I understood your post, I took the terminal with no voltage to ground disconnected it and read continuity to the metal hood range cover with the muti pin plug disconnected from the control board. More specifically I read 1.4 ohms with the leads shorted out and 5.6 ohms when checked as described. I know attwood has on their web site how to check the control board with an ohm meter which I will do tomorrow.

dougrainer wrote:
Very Simple. The Water Heater does NOT pull even 3 amps when on LP and maybe 4 amps if you have 120 and that is to close the 120- 12 volt relay. IF you get 11 amps, that indicates a short. The water Heater wall switch just sends a 12 volt signal to the water heater control board. SO, the odds are, the wire from the wall switch to the Water Heater is shorted somewhere. To verify this, go to the water Heater and disconnect the multiplugs on the Water Heater control module. IF the short stays, the problem is from the Water Heater to the wall switch. IF the short goes away, the problem is in the water Heater itself. There is no cause for concern because the Water Pump and the Water Heater are on the same fuse. The Water Pump does NOT have to be on its own dedicated fuse circuit. The standard Water Pump hi output amp draw is dependent on the gallon flow rate and the PSI. But will never go over 10 amps. Most usage will be 7 to 8 amps. Doug

. I just stopped for the night tried your suggestion. Pulled the multi plug and the fuse still blew. I tried tracing these wires backwards but they disappear on top of the gas tank. Will look again in the day time.

My concern that 11 amps with water heater alone likely means close to 9 amps of EXTRA power going through that circuit. That is enough to cause overheating or perhaps even a fire (9 amps times 13 VAC= 117 watts). If in a confined area, that is a lot of HEAT.