The used Rusco heater that I installed worked for a while. The Emeter
shows the current draw to be about 5-6 amps from the pack. But when I
turn the temperature knob down so it electrically shuts off the
heater, the truck faults. According to Dolcom it’s an isolation fault.
An ohm meter from each heater element lead to ground showed about 3-5
meg ohms. It showed infinite resistance when it not installed in the
truck.

After rechecking everything, like maybe wet heater element wires, I
turned the key on one more time. It booted. I turned the selector knob
to heat, and rotated the temperature knob to about the 1 o’clock
position and the pump and heater element came on. Rotating the
temperature knob counter clockwise to turn off the heater, faulted the
truck again.

This truck does not have the orange button to push to turn the heater
on. The heater enable is tied into the truck’s factory heater controls.

The most important part of tonight’s exercise was to make sure the
pump was primed so the heater didn’t smoke. It took way longer, and
was far more difficult than I thought, to get the pump primed. Make
sure you can see the fluid running back into the reservoir before
turning on the heater element. The way I fired up the pump separately
from the element was to remove the green relay inside the small gray
plastic box bolted to the side of the heater box. The highest pin in
the relay socket was the normally open connection that went straight
to the pump. Ground was just the heater box surface. A separate 12v
battery came in very handy.

In case this used Rusco heater is really kaput, I grabbed the 1500W
Kim Hotstart heater like George installed last year, and it looks like
an easy fit behind the Dolphin but outside of the heater box. I could
leave the old Rusco heater installed, but move the wires over to the
Hotstart. That way plumbing to the Hotstart would be very easy and
quick. It would just need to mounted to the Dolphin frame or something.

However, if the pump gets moved down about 3/4″ inside of the box and
one mounting ear of the Hotstart heater is cut off, the Hotstart will
fit inside the factory heater box with just a mounting bracket
required. This is food for thought. It would make for a clean install,
but more work. I’d rather spend my time getting the tilt bed hardware
installed if it arrives tomorrow. I’ll see how I feel tomorrow.

The Rusco is rated at 1000w per the label. The Hotstart is 1500w. Both
of those ratings are at 240vac. With 325vdc running through them, the
Hotstart heater would be about 1800 watts. This could be a nice
improvement over the weak factory heater. And as George pointed out,
with a plastic bodied heater, no more ground faults.