HI,
I fully understand the use of a block heater, but am wanting to get the air heater working if I don't have 110V available to me. Minnesota people need easy starting diesels. It's really fun when the temp drops to -30. I am a certified Detroit person, but that was 20 years ago when everything was mechanical.
I would like to update what I have found. The specs on the air heater is, it should come depending on the temp of the engine and the air temp. Combine air temp and engine temp and the spec is 130 degrees. If the air is 50 degrees and the engine is 50 degrees the heater will come on. If the air temp is 20 and the engine is 120 the heater will not come on. All that being said, my heater is coming on at lower temps. I'm guessing around 110 degrees. Not a big deal, as the actual problem that I had was more complicated.
1) Fuel pressure regulator was leaking, allowing fuel pressure to bleed down with time, meaning more cranking after sitting. Replaced that. Helped but no cigar.
2) Main issue was, I was not getting power to the air heater relay. I tracked this down to a defective 130 amp breaker. On this same panel was a similar breaker providing 12 v power to the chassis. Loose that breaker and you are done traveling. These breakers are a poor design with many failures. The air heater breaker just crumbled when I touched it.
I was not able to get much help from Freightliner as they kept giving me info for the Cummins chassis. Then said the circuit breaker was inside the frame rail next to the tranny. I was not able to see the panel with the breaker on it from below, but did finally track a couple of heavy wires going straight up towards the bed area. This took some time and many trips for a gimpy old man on the ground.
From the top I was able to finally locate the panel and am getting heavy duty breakers to replace the air heater and coach crappy breakers. I temporarily shorted the air heater breaker and at 40 degrees the MH started in less than 2 seconds and ran smoothly.
Wheee.
Dave