BN-4 Heater Timer

tnjanderson · Posted: Sat Jan 01, 2011 11:14 am Post subject: BN-4 Heater Timer

Hi folks! I've read all of the BN-4 related postings, but do not see anything describing my situation. Basically, after running for 3 minutes or so, my 16 amp fues (the one in the fuse box) pops and everything shuts down. I've tested the motor points, cleaned the flame switch, etc., but no joy. I suspect the problem may be in the timer switch, but cannot find any postings discussing how to test the timer. I have the THING Shop manual, but it does not give much information on the timer itself. Can anyone help me with a timer test procedure? Many thanks in advance!

Captain Spalding · Posted: Sat Jan 01, 2011 11:41 am Post subject: Re: BN-4 Heater Timer

tnjanderson · Posted: Sat Jan 01, 2011 4:03 pm Post subject: BN-4 Heater Timer

Captain Spalding:
Thanks for the reply. I first started the heater up and let it run. At about 2 minutes, the 16 AMP fuse blew. I turned the system off and put in a new fuse immediately. When I did so, the fan came on (even with key and switch off) as I would expect --- the cool down cycle. When it shut down, I crossed the red and gray wires. 16 Amp blew immediately. Then I crossed the black and gray, turned the key on and blew it again. I guess the problem is not in the switch at this point. Any other thoughts on what I might try in my efforts to run down the real problem?
Manya thanks in advance!
tnjanderson

Captain Spalding · Posted: Sat Jan 01, 2011 4:39 pm Post subject: Re: BN-4 Heater Timer

Hmm. Strange that there was a delay with the switch but none with simple crossing of wires. For no logical reason I'm tempted to suspect a short before a component failure. I guess step one would be to check out the gray wire and the solid blue wire - check the connectors at the ends and check for continuity to ground. Have a look at the relay and the other components on the heater and make sure none of the connectors are touching one another, particularly the safety switch (where the gray wire connects).

Emeritusx · Posted: Sat Jan 01, 2011 5:44 pm Post subject:

The heater is lighting right? And runs for awhile blowing hot air before the fuse pops?

When the thermo-switch flips could be when the fuse pops.

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Captain Spalding · Posted: Sat Jan 01, 2011 5:55 pm Post subject:

FYI, other BN-4 circuit diagrams in the Samba technical section, here and here.

[email protected] · Posted: Sun Jan 02, 2011 8:58 am Post subject:

sounds like either your gas pump is not working or your spark plug is dirty
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tnjanderson · Posted: Sun Jan 02, 2011 12:11 pm Post subject: BN-4 Heater

Thanks Emeritusx, Captain Spalding and Mike Brasso. I have cleaned and checked everything and concluded it must be in the thermo switch inside the Flame Sensor, or possibly the Safety
Switch --- or a combination of the two. I add in the Safety Switch because when I disconnect the fuel pump (by removing the 8 amp fuse), the fan motor will continue to run essentially forever. I thought it might be the cold air keeping it running, but when I put my torpedo heater next to the car and put a lot of hot air into the fan intake, the fan still runs on forever. I quit timing it at 10 minutes. So, problem still persists. Heater comes on just fine, but after 2 to 3 minutes, the 16 amp fuse blows. When I immediately put in a new fuse, the fan kicks in until the appropriate cool-down period is passed.
Any additional thoughts before I start buying parts on a trial-and-error approach????
Many thanks in advance
tnjanderson

Emeritusx · Posted: Sun Jan 02, 2011 2:06 pm Post subject:

So it never lights? you never said if it was blowing heat..

tnjanderson · Posted: Sun Jan 02, 2011 2:17 pm Post subject: BN-4 Heater

Folks:
Sorry for the confusion. The heater does light up and provide heat as normal --- just quits after about 3 minutes when the 16 Amp fuse blows.
Any additional thoughts????
tnjanderson

Emeritusx · Posted: Sun Jan 02, 2011 5:05 pm Post subject:

That pretty much rules out the cold circuit, and the fact that your heater fan never shuts off means it doesn't seem to be going back to cold ... I would start with the thermal-switch. Using the diagrams the captain left (print them) you can isolate circuits, it maybe something as simple as a wire is touching ground and when the flame good signal goes true that circuit grounds out.
Does this with ignition on and off right? that would rule out the dash switch.

tnjanderson · Posted: Mon Jan 03, 2011 8:01 am Post subject: BN-4 Heater

Emeritusx:
Thanks for the input. I'll be the first to admit I don't fully understand the diagram provided by the Captain, but I'll try to get someone to help me with that. Am I correct in assuming the thermal-switch is in the Flame Switch, and thus that might be the fist thing to replace?
Thanks again to all who are contributing to my problem resolution!!!
tnjanderson

Captain Spalding · Posted: Mon Jan 03, 2011 11:54 am Post subject: Re: BN-4 Heater

tnjanderson · Posted: Mon Jan 03, 2011 12:15 pm Post subject: BN-4 Heater

Captain Spalding:
I tried that yesterday as I was attempting to get the Safety Switch to work properly. When the fan is runing, I can activate the switch and things shut down as expected. I also activated it several times (no power applied) during some of the other troubleshooting efforts. Given that it does not operate as the heater maintenance manual suggests (i.e., does not shut down after 120 - 180 seconds with the fuel pump disconnected), I'm pretty sure it is defective. I'm just not sure if it is a separate issue unrelated to the 16 amp fuse blowing, or a direct part of the fuse problem.
More testing once I get some additional fuses. thanks for your inputs!
tnjanderson

29thSS · Posted: Mon Jan 03, 2011 1:05 pm Post subject:

Ok, I have heard these things turn into flame throwers after time. Is this true and if it is why not switch to an electric heater?

Emeritusx · Posted: Mon Jan 03, 2011 5:12 pm Post subject:

29thSS · Posted: Mon Jan 03, 2011 5:47 pm Post subject:

Well hell thats cool. I guess I am going to get to work on min them as it is 17 degrees outside and I would like a heater. Thanks for the info man.

Captain Spalding · Posted: Mon Jan 03, 2011 7:58 pm Post subject:

Emeritusx · Posted: Mon Jan 03, 2011 8:28 pm Post subject:

thanx
Ladder (relay) logic is my forte... Above all else.. I tinker in vw land and am at best an apprentice mechanic, but that kinda stuff I really love to do and am good at. It is the language that runs almost all automation in the industry, but is slowly becoming old school...

Captain Spalding · Posted: Mon Jan 03, 2011 9:32 pm Post subject:

Okay. Now that I've stared at the ladder diagram, I'm becoming a fan of the if/then/else nature of it. But, as I look at the ladder diagram and compare it to my wiring diagram, I don't think it jibes. I'm not saying one or the other is wrong - maybe I just don't get it. But could someone look at both and compare?

Edit: I think the logic is correct, but the labels might be switched in a few places. Check me on this. Third rung down, hot and C should be reversed, no? And J and B on the relay (CR)?


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