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Thread: H-1 Ground Support Heater, NSN 4520-01-056-4269

  1. #21
    4 Star General Wire Fox's Avatar
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    Quote Originally Posted by Guyfang View Post
    It doesn't have a vent position? To vent the burner chamber? Is the flame controller a photo electric device?
    "vent position" would be just switching the burner itself off, as the blower is on if the engine is on (direct mechanical drive). That main 3-pos switch controls the engine. The burner is operated on a separate circuit, which has safety sensor interlocks for high temperature, airflow, and presence of flame. Lack of any of those will cutoff the power to the ignition coil and fuel solenoid for the burner itself.
    Last edited by Wire Fox; 06-12-2019 at 17:32.
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

  2. #22
    4 Star General Wire Fox's Avatar
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    Attached is the way easier to read schematic, with my annotations of info pulled from the text of the patent.IMG_20190612_173344.jpg

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    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

  3. #23
    4 Star General Wire Fox's Avatar
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    Confirmed that the unit is indeed...wired wrong. And the spare panel I have? Also wired wrong. Both of these are setup with 24V going straight to the power input. I spent some time carefully reading the water-damaged label on the ignition control module and was able to decipher 05-159901-003. This P/N crossed over to NSN 4520-01-065-3858, which immediately points back to being a part for a Davey / DRS H-1 heater. Perfect! Also good: I found a cheap replacement part online ($23 delivered, sealed in military packaging) that so happens to have a very legible label. Attached the picture below... As well, I found a Kidde-Fenwal reference sheet. This obsolete P/N crosses over to be a 35-530501-103 (Doesn't appear to be a 1:1 replacement, also was declared obsolete). An additional note stated "COLEMAN 4322-321, DIRECT REPLACEMENT" I found the old datasheet as well, so attaching it (includes P/N for wiring harness, P/N for the electrode assembly that has same dimensions as what's in the heater, the gap measurements for the electrode, and a block diagram of this unit)...
    Fenwal 05-159901-003 Ignition Control Module.jpg
    As you can see, the input clearly states it's supposed to be 12V. Sadly as well, I found no trace of a resistor inside the control box assembly to try and measure any value for the prior schematic. What might the value be?
    (As a voltage divider, the actual calculation for the two voltage sources with the unknown resistance looks beyond my pay grade.)
    Worst case, I can just tap off of a single battery and completely disconnect the 24V side. That should at least provide the ignition controller with a safe 12V for operation, just forcing me to keep my eyes on the batteries for regular maintenance. Alternatively, I could just replace it with a 24 VDC model and gamble on all of the rest of the specs being right... 24VDC input, 24VDC valve, no purge cycle, 6.8 sec flame establish time... Hypothetically would be 35-405200-003, but I'm getting no hits for it being out there. (And at $23 vs $250, it's more cost effective to make the original 12V unit work...)
    Attached Files Attached Files
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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    Guyfang (06-13-2019)

  5. #24
    4 Star General Wire Fox's Avatar
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    Lots of back and forth on this one on paper. Got a hold of a friend that's adjacent to the AF and like a good boy, wouldn't let me see the manual, but he was happy to hear out my troubles and look over the manual himself and provide some advice. On the circuit, he indicated that the latest revision simply drops the impeded 24V connection for the ignition circuit: it's simplified to just opt for an imbalance of the batteries as an acceptable maintenance condition. To simplify the wiring to the batteries, prevent imbalance, and support slave start operation without its own batteries installed, I'm just going to drop in a simple 24V -> 12V waterproof converter. It looks like most of the rest of the wiring diagram is correct, so I should be able to follow along with what I have to make corrections to gauge and alternator wiring.

    As well, the heater is stripped down to the point that I only have the fuel tank, engine, and control panel attached to the trailer chassis. It's in the perfect state to get degreased, primed, and painted prior to reassembly. That should go a long way to keep rust away and also to make this thing look sharp. While I could get fancy with CARC, I don't think it's worth it for this project...I'll probably go for one of the Behr methods people have mentioned with good results, or mess with something like Rapco spray. Basically, anything that I don't have to spend a small fortune and over a week of prep work on to get ready to use for such a small device.
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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