BN4 Hardi Pump - not all the same!

[Angleofattack]

Hello again,

In my quest to overhaul my Pinzgauer BN4 heater, which would mostly run well but occasionally fail to start or start smoking black, I decided to buy a new Hardi pump, just because I suspected the old one was the culprit.

The reality is that after the overhaul, which included cleaning the original Hardi pump points, the pump would run everytime, and well, when fed with 24V.

But since I had the new one in hand, I installed it, and this is NO GOOD. When I start the unit with the new pump, something clicks, everything stops, and the orange fault light remains illuminated with the switch on the off position. I reset it by turning all power off, but even then, it requires time (10 minutes? 30? don't know) for the fault to go away.

The difference between the pumps is obvious. The original has one connector for +. As in the pre 69.
The new one has 2 connectors, as the post 69.

I believe I am dealing with this installation in my Pinz.

Does anyone has any idea why the new pump wont work in my configuration? I just assumed the only difference was the need to ground the motor from the connector instead of the other one being grounded from the pump body.

Many thanks,
Jeronimo

[busdaddy]

Does the new pump look like this one:

If so it's for the 1972 and later system which uses pump timing points in the blower motor opposed to points in the pump. It pumps a specific amount with each click and eliminates the need for the regulators, but sadly it's not compatible with the early style system.
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[Angleofattack]

Here are the pumps I am taking about.
The red one does not work in my installation.

[busdaddy]

That's really odd, it looks like the typical constant flow pump just like the OG one aside from the external ground. Looking at that diagram (we should call one pre 70 and the other 70+ since the new model year begins Aug 1) the only difference is the color of the wire and a body ground for the bonus wire. Have you tried swapping the wires and using the brown (-) as power and grounding the + wire?, those pumps don't mind reverse polarity (unless it's internally grounded as well, test the - with a meter to the pump body for continuity).

What device decides it's time to turn on this light?, I see only one light bulb in that Pinz diagram (and suck at reading German), is it on as long as the heater is happy?, or does it do many things?
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[Angleofattack]

Dear Busdaddy,

I really appreciate your time reading my posting. Thank you.
Quite interesting are your ideas. I will check the polarity of the new pump and see if it is wired differently.

Regarding the light, based on my experience, it has more than one function. One is when running, the other is when the unit faults. Not sure about the logic, and if it is working ok.
When I get home in 10 days I will read the manuals, maybe there is something about it in the trucks user's book.

Thanks again,
Jeronimo

[Angleofattack]

Well, I can't explain. I tested the new pump again, this time as suggested, with the positive grounded, and the heaters power positive to the negative connector.
It started right away... but this did not make sense, so I tried again to reproduce the fault I was getting before and nothing.
The new pump now works one way or another.

The only explanation is that maybe the first time I tested the new pump, my batteries were low. Would the BN4 have a low voltage protection?

JC