Sububan hot water heater - not hot

this problem was a comedy or errors ans assumptions... When operating the HW heater on 110VAC, there is a third wall switch in the bathroom that must be on to operate the system... This switch has a light on it to let you know the HW heater is on so we can only assume that the was an add on by the previous owner (but why 3 switches???)... as for gas operation, a twist nut connection on the control board ground lead was loose.. (Twist nut on RV???) Now he has HW but not at a cost... 2 hrs labor at RV shop...$$$$$$$

Dick_B wrote:
I'm curious if they ever used their heater on electric. If not there could be many sources of problems.

Owner said that the previous owner did turn of the electricity for the HWH but only when gas was already heating the water during the purchase walk thru (used unit) ...SO... he can't say for sure if it worked or not only on electricity.. he only assumed it did... He left this afternoon for a service shop as they wouldn't stay without hot water.. should be back later today or tomorrow and I will post what was found... I'm betting that the electric element has been burnt out by the previous owner which would explain the electric failure, and that the problem is in the control board for the 12v/gas operation as the resets had no impact and 12 vdv power was available... Thanks for responses...

I'm curious if they ever used their heater on electric. If not there could be many sources of problems.

Suburban uses two (2) separate/independent systems----12V DC for propane and 120V AC for electric.

120V AC is wired directly from AC circuit breaker to AC junction box on side of tank to ON/OFF switch in outside compartment to/thru Hi/Normal set of t-stats to electric element and then to neutral. (Does NOT use control module or 12V DC to function)

12V DC is wired from DC Dist. Panel fuse to ON/OFF switch to DC junction box on opposite side of tank to/thru Hi/Normal set of t-stats to control module which DC power to gas valve solenoids and spark electrode.

One system failure would not affect other system.

Check if Hi t-stat(s) have tripped------------'Push to Reset' rubber cover in outside compartment
Left side is 120V AC set and Right side is 12V DC set

Check that electric On/Off switch is ON in outside compartment for electric

Blown DC fuse, tripped AC circuit breaker, loose connections in junction box(s), bad connections on t-stats, shorted wire(s)----check wiring to/from t-stats

Digital voltmeter and start checking where power is and isn't------AC & DC
Visual checks of connections on t-stats
Good/clean/tight grounds

Outside on the end of the heater under a rubber pad are two thermostat control reset buttons. One is 12v other is 120v. Check them first. Of course that won't tell you what tripped them if they need resetting.

The Suburbans have separate systems for 120 and LP heating.
I would start with one system and work through that problem.
LP:
Check to see if 12 volts DC is getting to and from the switch.
If getting to the switch check for the 12 volts getting to the circuit board. The ECO or thermostat could be open preventing this from happening.
If power and ground are getting to the circuit board listen for the ignitor to operate. Power and no ignitor, time for a Dinosaur Electronics circuit board.
120 volt AC: Many have two switches the one inside the rig and a service switch on the outside access. Carefully verify whether 120 volts AC is getting to the element side of the switch. Check to see if the reset on the thermostat is good.
Many possibilities on each system.

Make sure it actually has 12V at the heaters circuit board.