Bn-4 gas heater points keep getting fouled

[hylomatt]

So recently picked up a 1973 Volkswagen Thing about 4 months ago. I've been on a pretty hardcore kick to restore the thing for a trip from Florida to North Carolina and back just after Christmas this year.

One of the important elements is getting the heater working. I have one good heater and another that can be used for parts if I have to but it could also be working. Only the one works at the moment though. I've taken the heater apart 5 maybe 6 times now and to varying degrees of effort have cleaned it and gone through the heater manual that I picked up from Michael Basso and made all of my adjustments for timer cut off heat safety settings, etc.

My problem is that after about 30 to 45 minutes of operation the pump starts to miss Beats. And eventually it'll Miss enough to kick off the safety switch and then of course the heater stops working then I have to reset it. Once I reset it it's just as unreliable. Sometimes I wake up the next day and cut it on and it'll be fine for another 30 to 45 minutes.

Last time I removed it from the car I hooked it up on my bench and took the motor completely out of the housing wired it directly to the pump and got the same kind of unreliable Behavior. So I took it apart and cleaned it cleaned the points filed them again and slightly adjust the points so that the Gap was a little Les and the connection would be better when the points came close enough together. This worked for a couple days almost a week but now it's doing the same thing again.

Does anybody have any advice on how to resolve this? Or is this possibly normal? I live in Florida and it's pretty humid so that could have an effect on it as well.

[doublecanister]

hey Hylomatt,

as a reference, my 73 THING's heater had been broken since the PO owned the car, best guess 8 to 10 years.
Ended up the fuel pump was frozen stuck.

after breaking it loose and running it for a few years I'd pop a fuse or have to reset the breaker, I ended up not running the heater on the highest heat setting and all that seemed to stop or so far it's helped.

I pull the thermostat all the way out then push it in about1/4 an inch or so and it's hot enough for heat but not so hot i'd use it to make smores anymore!

Not sure how long yours has been sitting but if the pump is getting stuck or if it's related to it temperature (they have some sort of a safety temp sensor circuit built in), if you try it again see if it will run on a lower temp..

I think there are wire diagrams on the samba in the technical section, I've seen them on here before...

Also, I'm not an expert here so hopefully others will chime in too just some of my exp...
Good luck!
T
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2020 - Mustang Eco Boost [High Performance]
1973 - Thing
1966 - Mustang GT- Fastback
1951 - Ford F1 pickup Flathead V8

[hylomatt]

@doublecanister, thanks for the reply. the pump works great and is strong after cleaning, etc. i sat and tested it for 10 mins straight before hooking it up and running it for a 1hr and 15 min test on the bench.

for the record, i conducted the most minimalist test i could come up with on the motor + pump. the fan motor was removed from it's housing and supplied with 12v from a bench battery to it's black and brown leads. then the pump was hooked to the same power on the black lead and to the green lead out of the fan motor.

the last time i had to pull it for intermittent pumping, it continued this behavior on the bench with the setup described above. after cleaning, filing, and adjusting the points gap, the intermittent pumping behavior was eradicated once again. put it back in the car, ran it for almost a week and now it's intermittent again.

i'm about to take it out and do that all over again in the next 15mins. getting a little tired of the wash-rinse-repeat nature of this revolving issue.

i get having to reset the red switch from time to time but the points shouldn't be getting fouled over and over again, imo. i must be doing a shoddy job at cleaning them properly.

anybody have any advice on anything that i'm not understanding or misinterpreting, etc? i'm guided by the eberspacher heater repair manual and as much common sense as i can scrape together here. i'm not giving up but damn it, can't this thing work for a few weeks at least

[kenj06]

Thinking about the points in a distributor and looking over the wiring diagrams for the heater, I'm guessing the condenser(capacitor) across the points is shot, broken or missing. The condenser across the points absorbs some of the energy transferred by the points and prevents arcing which will foul the points. Sorry I don't know the replacement part but considering 12v is traveling through it, a condenser off a distributor may work. I would start with that.
Could also be the pump drawing an excessive amount of current.

The condenser is shown on this diagram:
http://www.thesamba.com/vw/archives/info/wiring/Thing_Eberspacher_BN4_Heater_Wiring.pdf

Good luck!

[hylomatt]

@kenj06, thanks for the advice. i hadn't thought of that. i went back and read the manual looking for info about the capacitors that are present. all the heater manual says is replace if points are pitted. well, they weren't pitted but they were dirty.

i took the heater out of the car again, disassembled it down to the blower motor, hooked it up to a power source and test light as described in my 2nd post, and it was missing beats according to the test light. then, while it was running, i slipped a shop napkin between the points as they were in operation and moved the napkin back and forth making sure to let the points grab it just a bit along the way. it cleaned a bunch of shit off of the points. the points that i had cleaned just a week ago. then the test light was giving me good info after that.

this time i took the points off and wiped up ever bit of crud i could find anywhere under that butt-capped end of the motor. tested for ~ 10mins, reassembled the heater, tested again until the switched kicked off the heater and then again. reinstalled into the vehicle and went driving for an 1.5+ hrs.

it performed beautifully. i'm getting good at working on these things. i really hope this doesn't occur again anytime soon but it's rather easy to do and i'll just bring the tools with me should i need to go at it again.

[Wildthings]