So now the Hotstart heater is mounted in the heater box and the whole
assembly is back in the truck. Nice and clean.

As for operation, the ground fault issue appears to be gone. But I did
find what might be a factory defect. When the selector knob is set to
Heat, then by taking the temperature knob and rotating it clockwise
for warmer air, at about 2:30 o’clock the heater element comes on,
then at 5 o’clock the pump comes on. Say what?? The heater element
comes on without the pump coming on. This could be the very reason
that the heater never worked for the first owner. Someone toasted it!
It would overheat itself since there was no water flow. I have a
diagram that shows some changes to that very circuitry. I’ll look into
it.

The Hotstart heater draws 8 amps at 321 vdc compared to 5.7 amps with
the stock heater. It rose the defrost vent temperature from 75F to
135F in just a couple of minutes. Then the built in temp sensor on the
Hotstart tripped and shut off the heater element, but the pump keeps
running. After the defrost air went down to about 94F, the heater
element kicked back in. We’ll see on a cold night if this repeats
itself. 75F ambient is a very hot place to start a heater test. The
great news is I have an original heater in one truck and an improved
heater in another, so performance can be compared.

Again priming the pump was a pain!! The fastest way was to pull a
vacuum on the output hose that comes off of the firewall until I got a
mouthful of coolant. Then it was primed. Yuk. I could see this heater
smoking instantly without the system primed. It might almost be worth
using clear tubing just to see if there is flow.

The bed hinge hardware arrived today. Too bad I’m so tired. I’d love
to get that done so I can get at those batteries. I suspect they are
dried out as the pack voltage is fine, just hardly any amp hours. If I
could get 5 miles out of this pack it would help testing and even
allow a trip to the car wash.