Thermotop C startup problem

[Silebyman]

Proper marine thermotop has decided not to start when batteries below 100%
Got solar and started  happily when sun out this morning.
I’ve got a fairly recent set of batts, and at smart gauge 95% this evening it wouldn’t go, and needed engine on to get heater to fire up. 

Once it’s running it’s fine. 
Have I got a high resistance somewhere , or needing a decoke? Any ideas?

[ditchcrawler]

Bad connection on a fuse or connection between battery and heater

[Silebyman]

Might be dumb question but how do you check voltage at heater during start up? I’m assuming you don’t unplug the connector, and back of plugs are sealed. 

[Tracy D'arth]

Spike probes through the insulation, I use map pins, they leave smaller holes.

 

Recent problem or some time?

 

Wiring too thin giving volt drop when under heavy load from heater ignition element?

 

99.99% of blown diesel heater start up fails are due to low voltage when heater ignition element load is on.

Edited March 26, 2022 by Tracy D'arth