Testing the Dosing Pump


New member
Hey everyone!
I have a 2005 140" I bought in February of this year and I've never been able to get the espar heater to fire up. It doesn't have the 7 day timer, it is just the heater booster one. I've been trying to trouble shoot the problem and first tested and found the coolant pump to be shot. Replaced that, still no luck. Using a volt meter, the heater seems to be getting power so I moved on to see if it was getting fuel. Nothing. The line is totally dry. Went under the van and found the dosing pump and it has power to the wires but from what I'm reading it goes on a waveform? I don't quite understand it, but either way, the pump doesn't seem to make any noise or do anything when I hit the heater booster button. Is there a way to test the pump? Or is it likely shot? And I've scoured this website and the internet and can't for the life of me find where to buy a replacement dosing pump. Any suggestions?

Thanks everyone!


The pump should list voltage on it. They come in both 12 and 24 v versions. You likely have 12V version in your van. You could hit it with 12V and see if it does anything. It should click. Polarity does not matter on the solenoid.

You can get replacement pumps from Espar suppliers online. I assume it depends on which heater you have.

You can 'scope' the output of the heater. It should put out a pulsed waveform. A multi-meter usually falls a little short with this type of diagnosis.

Aqua Puttana

Poly - Thread Finder


Well-known member
Confirm it is a pulse pump.
We use a tech's power probe to pulse it up.

You simply need a flick switch with two wires one going to ground to cycle the pump to see it it pumps or in fact actually works.
All simple stuff really.

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