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Heater fan running on it's own
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HMVWNAB
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PostPosted: Wed Jul 27, 2016 3:03 pm    Post subject: Heater fan running on it's own Reply with quote

Came home from work and went into garage and heard the familiar sound of the heater fan blowing.

Figured someone turned the timer switch on and went to turn it off and found out it was already in the off position.

Removed the fuse to stop the fan and dropped the dashboard panel to disconnect the timer switch from the harness. Reinstalled the fuse and the motor started up again.

Wiggled the harness to see if the motor would cut off and on, but it wouldn't. Started car and futzed with the lights, wipers, etc to see if anything affected it, nothing.

Anyone know offhand what else is on that circuit that could be shorting the on/off to the fan motor?

Seems odd it would just go bad sitting in the garage. Battery was still charged enough to start car, so I must have just caught it.
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mondshine
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PostPosted: Wed Jul 27, 2016 3:28 pm    Post subject: Re: Heater fan running on it's own Reply with quote

Stuck relay under the big cover? Maybe a careful tap-tap will free it, but you will need a permanent fix.
Do you have the wiring diagram for the heater?
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KAmes
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PostPosted: Wed Jul 27, 2016 5:13 pm    Post subject: Re: Heater fan running on it's own Reply with quote

This happened to me, in my case it turned out to be this switch
Image may have been reduced in size. Click image to view fullscreen.


I'm no expert on these by any means, the mechanism working this switch seems to sense the temperature inside the chamber and controls how long it runs on after you turn it off. I discovered the heater would stop if I unplugged this so I removed it and found with an ohm meter that it was stuck. Replaced with a good used one and all is good. Be aware behind the switch where you can't see is this screw (the red one, not always red though)
Image may have been reduced in size. Click image to view fullscreen.


turning this one way or the other physically moves the switch and adjusts how long it runs on, could just be out of adjustment. If you mess with it keep track of how many turns so you can find your starting point again, its sensitive. Might be something else, maybe a problem with the timer switch? Was it just blowing, not burning? Someone who knows more will probably post the answer, but this was my experience.

I believe this switch also has bearing on how long the glow plug burns on startup, just to muddy the subject.
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KAmes
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PostPosted: Wed Jul 27, 2016 5:28 pm    Post subject: Re: Heater fan running on it's own Reply with quote

I just re read and saw you unplugged the timer switch, so not that. I would start with unplugging the switch indicated and see what happens. Trouble shooting manual under the technical tab here (although I haven't read it yet)
http://www.thesamba.com/vw/archives/manuals/bn4troubleshooting.php
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PostPosted: Wed Jul 27, 2016 6:34 pm    Post subject: Re: Heater fan running on it's own Reply with quote

The component that KAmes is pointing to in the photo is called the Flame switch. (F16 in all the drawings.) Have a look at the BN4 ladder diagram here.

Find the flame switch on the diagram. It has two purposes. When the heater is cold, the switch energizes the glow plug. After the heater warms up, the switch disconnects the glow plug and moves to the hot side. When the fan is running, there are two conduits of power to the fan. One is the relay. The other is the flame switch. While the relay is in operation the flame switch is redundant. But when the heater is turned off, the flame switch continues to power the fan to allow unburned fuel vapor to be vented from the heater until the interior temperature of the heater has cooled sufficiently. When the heater is cool enough the flame switch moves back to the "cold" side and the fan turns off.

Your situation likely indicates that the flame switch is stuck rather than out of adjustment. Before turning the red screw, I would try freeing up the flame switch just by articulating it. Try freeing it with fuse out, and then put the fuse back in and see if the fan has stopped running while the heater is off and cold.

If that seems to solve the problem, you might want to put a couple of drops of oil on the flame switch mechanism to help prevent it becoming stuck again.

If you take the set screw out of adjustment you will be hard pressed to make it right again. The literature is a little thin on that procedure.
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HMVWNAB
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PostPosted: Thu Jul 28, 2016 4:40 am    Post subject: Re: Heater fan running on it's own Reply with quote

Thanks for all the helpful replies. I was out last evening and didn't get back to it. Truth be told I have never used the heater.

If the adjustment of the flame switch is so finicky, is that because it's adjusted like points in a distributor? Is the gap that small?

If so, is it possible that the temperature in the garage caused the metal to expand enough to make contact?

We've been in the 90s lately.

I will investigate this evening.
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KAmes
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PostPosted: Thu Jul 28, 2016 6:54 am    Post subject: Re: Heater fan running on it's own Reply with quote

HMVWNAB wrote:

If so, is it possible that the temperature in the garage caused the metal to expand enough to make contact?

This idea occurred to me too, but I don't know the answer.
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PostPosted: Thu Jul 28, 2016 11:50 am    Post subject: Re: Heater fan running on it's own Reply with quote

HMVWNAB wrote:


If so, is it possible that the temperature in the garage caused the metal to expand enough to make contact?.


A heat gun would answer this real quick! Interesting thought... Although I'm sure plenty of folks in Much warmer climates would have experienced this phenomenon sooner.....(?)...
I don't recall ever seeing this issue before....(although with my Memory, that's not saying much, Wink )

Interesting to see what you find out...
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PostPosted: Thu Jul 28, 2016 1:29 pm    Post subject: Re: Heater fan running on it's own Reply with quote

For what it's worth, the references in the heater manual to the flame detector switch:

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PostPosted: Thu Jul 28, 2016 2:07 pm    Post subject: Re: Heater fan running on it's own Reply with quote

just saying,

My heater "timer switch" was broken when I got the my 73' THING,

if you turned in on to run the heater, it would not timer down to off.
Had to do that manually and guess at about 20min or so run time.

So, as the guys are saying it's probably not the culprit.

It's weird though and It's good to know this can happen.
I may should start disconnecting my battery more often just to be safe.

If you don't use the heater you could disconnect it all,
but if you can I'd fix it.

Mine was said to need $800 worth of parts by the PO,
but it was just a frozen fuel pump after all.

Good luck with it

T
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HMVWNAB
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PostPosted: Fri Jul 29, 2016 4:31 am    Post subject: Re: Heater fan running on it's own Reply with quote

Looked at the flame switch as was suggested.

Hit it with some freeze spray but that did nothing.

Tried to manually move the slider mechanism at the rear of the switch back and forth with my finger but it did not disconnect the fan from turning.

When the spade lug leads were removed of course fan stopped working.

Need to check to see if there is supposed to be voltage at the input of the switch at all times.
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KAmes
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PostPosted: Fri Jul 29, 2016 8:15 am    Post subject: Re: Heater fan running on it's own Reply with quote

I believe it would have to have power to it all the time in order to facilitate the cool down function. In my case i removed the switch itself for testing without disturbing the mechanism going into the chamber. Later when I'm near the car I'll test which terminals have voltage when it's off.
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PostPosted: Fri Jul 29, 2016 9:25 am    Post subject: Re: Heater fan running on it's own Reply with quote

HMVWNAB wrote:
Tried to manually move the slider mechanism at the rear of the switch back and forth with my finger but it did not disconnect the fan from turning.

Did it move? Or was it frozen?

Quote:
Need to check to see if there is supposed to be voltage at the input of the switch at all times.

Yes, there is supposed to be voltage all the time, via the red wire.

Two notes:
    There are wiring diagrams for the heater in the technical section.

    If your heater is like mine, there's a Molex type connecter under the
    hood that you can use to simply unplug the heater. That way you don't
    have to keep pulling and replacing the fuse.
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PostPosted: Fri Jul 29, 2016 10:27 am    Post subject: Re: Heater fan running on it's own Reply with quote

Yes, the slider moved quite easily, just didn't oscillate the power on and off.

And I actually used the freeze spray while fan was turning.
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PostPosted: Fri Jul 29, 2016 10:31 am    Post subject: Re: Heater fan running on it's own Reply with quote

Maybe it's time to start playing with the red screw . . .
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KAmes
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PostPosted: Fri Jul 29, 2016 1:01 pm    Post subject: Re: Heater fan running on it's own Reply with quote

HMVWNAB wrote:
Yes, the slider moved quite easily, just didn't oscillate the power on and off.

And I actually used the freeze spray while fan was turning.

On mine the slider will not disconnect the power, only reset it after the timeout has tripped. I measured just now and on the switch the red wire on the terminal most to the front of the car is 12 volts all of the time, the other two are not when the heater is off. When the heater gets up to operating temperature the terminal most to the rear with the black/yellow wires goes positive 12 volts, and stays that way until the heater has finished the cool down cycle after shutting the switch off. I'm thinking if the black/yellow wire is energized when the heater is supposed to be off, then the flame switch is stuck or broken or out of adjustment. I don't remember which way is which on the red screw, turn one way and the heater runs on longer (or forever) and then other way keeps the glow plug in longer and will cause the timeout to trip if too long as the system thinks it hasn't ignited. After replacing my switch I had to experiment a little.
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KAmes
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PostPosted: Fri Jul 29, 2016 2:04 pm    Post subject: Re: Heater fan running on it's own Reply with quote

The repair manual says rotate the red screw clockwise to decrease the shutdown time. If you have power at the yellow/black wire and it will stop blowing when you unplug it, I would turn the red screw in slowly while it is blowing and see if it stops. I believe it should unless the switch is bad. If it stops then start the heater up and see if it behaves. Small screwdriver, count the turns so you can put it back. Keep in mind I'm observing cause and effect on my own unit, I'm not an expert by any means. For that call Marty in Colorado, he sells heaters and parts in the classifieds. Seemed like a decent guy when I dealt with him, he'd probably fix you right up with what you need.

Step 6 page 17 here http://www.thesamba.com/vw/archives/manuals/bn4tro...manual.pdf

Marty http://www.thesamba.com/vw/classifieds/detail.php?id=1713788
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KAmes
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PostPosted: Fri Jul 29, 2016 2:22 pm    Post subject: Re: Heater fan running on it's own Reply with quote

I just noticed you can see the red screw really good in the picture in Marty's ad. Mine's really hard to see in the car. I bought one like that from him, it works really good.
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PostPosted: Fri Jul 29, 2016 6:12 pm    Post subject: Re: Heater fan running on it's own Reply with quote

FYI there are two flame switches in the Samba Classifieds. One of them is NOS.
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PostPosted: Sun Jul 31, 2016 6:44 am    Post subject: Re: Heater fan running on it's own Reply with quote

Captain Spalding wrote:

Your situation likely indicates that the flame switch is stuck rather than out of adjustment. Before turning the red screw, I would try freeing up the flame switch just by articulating it.



Image may have been reduced in size. Click image to view fullscreen.


When I originally responded to this I was referring to the component to the drivers side of the flame switch which has a mechanism to the rear and moves freely.

Is the FS supposed to move in an up and down motion like this? If so, shes stuck solid.
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