Vandog Traveller

How I fixed my propex (compact 1600) campervan heater – not igniting

I bought a second hand Propex heater (see my other post: Heating my van. Here’s how I installed a Propex heater) but it wouldn’t ignite. This post goes over how I fixed it. If you also have a Propex heater with this problem, this post might help.

Disclaimer: I’m not a gas engineer and I’m not qualified to give advice on servicing gas appliances. I’ll just share with you what I did. Best not to blindly copy me.

The problem with my Propex Compact 1600

The fan turns on but the flame doesn’t ignite and then it just turns itself off, after several seconds. The fault is intermittent – it fires up only about 5% of the time.

Fault finding

I read through the PDF manual (found here) and looked at the start sequence. I could hear the gas valve opening but there was no spark (should be a successive ticking sound before igniting the gas within a few seconds).

The problem is with the spark

The spark is generated with a high voltage coil (which converts 12v into thousands) and an electrode – similar to the ignition coil and spark plug in an engine.

Possible reasons for no spark

Before I dismantled the unit I spoke to a gas engineer and also a Propex technician and made a list of possible reasons why there might not be a spark (ruling out all external possibilities like a low battery, or lack of gas etc.):

  1. Faulty voltage supply to the coil. It could be that the internal power supply to the coil is faulty.
  2. Faulty HT lead. These leads have very thick insulation because they need to carry such a high voltage to the spark electrode. The rubber insulation can deteriorate and the voltage can short to the metal casing. I remember this happened in my old car and it gave a weak spark.
  3. Faulty electrode. The electrode body is made of ceramic. This can crack and can short the ignition voltage (similar to the above).
  4. Bad connections. Dry soldier joint or corroded connection. This could easily give a weak spark or no spark at all.
  5. Incorrect spark gap. If the spark gap is too large the voltage might not arc, resulting in no spark. Why the spark gap should be wrong I don’t know, but I was told by a Propex engineer not to be surprised if this gap was not exactly right on the older units such as this.

The propex Compact 1600 heater – under the hood

Testing and fixing

I went through each of the 5 possible reasons for no sparking (above) and tested each one.

1. Tested the supply voltage to the ignition coil (all good). I put a voltmeter on the supply Voltage contacts of the ignition coil (Black box mounted on circuit board – photo below) and monitored it whilst I turned the heater on. Immediately after the gas valve opened (a single click sound), the meter read 12V. So that’s all good.

2. Visually inspected the HT lead (all good). It looked like it was in good condition and was not perished or damaged at all.

3. Visually inspect electrode (all good). I removed the one screw that holds the electrode to the cody of the burning chamber. It looked fine with no cracks on the ceramic housing.

4. Checked connections (questionable). I removed the HT lead connected (with spade connector) to the the ignition coil. It looked fine but I gave it a light rub with with emery paper to ensure a good connection. The soldered connection at the electrode side looked questionable – dull dry solder. I desoldered and Resoldered it.

5. Checked and adjusted spark gap (this fixed it). It looks like the spark is meant to bridge between the metal wire electrode and the screw. Although the design looks a bit… makeshift? I’d expect the spark gap to be from the very end of the electrode to ground (the screw) but instead it seems to be a third of the way down of the electrode wire. I powered the heater up and watched the electrode to see if there was any spark at all. There wasn’t.

I decreased the spark gap slightly and cleaned the metal contacts with sandpaper

It now sparks every time

I gave the inside a clean before putting it back together

And resealed the casing with high temperature silicone

I had to break the existing silicone when dismantling. It’s important to add a fresh bead around all the casing edges that previously had it.


I Turned it on and off over 100 times and it’s ignited every time within a few seconds. It seems to be working 😃

EDIT: Spark gap was too small. Heater stopped igniting when I got over an altitude of 1000 meters – needs a more powerful spark to ignite with less oxygen and colder temperatures. I took the heater apart again and made it a big bigger. Works fine


I said before, if I wasn’t comfortable taking things apart I’d would have really regretted buying this gumtree heater and I would have lost a lot of money.

If I knew I’d have all this trouble I would have just bought a new Propex heater. But I guess I learnt some stuff.

So if you’re thinking of buying an old second hand heater propex heater, be prepared to either have to pay to get it serviced by Propex or take it apart and fix it yourself.

For photos of installation see this post: Heating my van. Here’s how I installed a Propex heater