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Here’s the 13 most common diesel heater installation mistakes….

…they’re the things that kept on coming up A LOT when I was doing research into installing this diesel heater I bought from eBay in our Jayco Swan.

The instructions that come with these things are terrible. Or non-existent.

(you can see how I installed ours step-by-step here)

This article should help with:

Reducing unnecessary damage.

Improving efficiency.

And most importantly:


Let’s get started:

1. Mounting the fuel pump horizontally

The piston in these fuel pumps cause tiny bubbles to form in the diesel.

And if the pump is on it’s side?

The bubbles can’t escape. They build up.

Diesel Heater Installation Mistakes - Fuel Pump Mounted Horizontally

This means the fuel pump wears out more quickly AND the heater doesn’t run efficiently

(it messes with the amount of diesel that reaches the heater)

This is the most common of the diesel heater installation mistakes… but it’s an easy fix:

The fuel pump should be mounted on a 15-30 degree angle to allow the air bubbles to escape.

2. Mounting the muffler sideways (or upside down)

See the little hole on the bottom edge of the muffler?

Drainage Weep Hole on Base of Diesel Heater Muffler

It’s a drainage ‘weep’ hole. It’s purpose is to allow water (a byproduct of the diesel heater’s combusion) to escape.

This muffler is mounted on it’s side:

Diesel Heater Installation Mistakes - Mounting Muffler On Side

Upside down, Miss Jane:

Diesel Heater Muffler Installed Upside Down

So yeah:

The muffler is mounted vertically, not on it’s side, to allow the water to drain out of the weep hole.

This was one of my diesel heater installation mistakes

[I learned that AFTER I’d initially attached it… so I took it off, flattened the bracket, and reattached it]

The good news is when I did this it made it easier for me to avoid another common installation issue:

3. Creating a low point in the exhaust pipe

One of the byproducts of the diesel heater’s combustion is water:

If there’s a bend in the pipe that’s lower than the exhaust outlet, water will collect there.

(and your exhaust pipe will rust more quickly)

Diesel Heater Installation Mistakes - Creating A Low Point In Exhaust

The exhaust pipe should slope slightly downwards to prevent water from collecting at the low point. 

4. Replacing the fuel line with automotive fuel hose

The hard nylon fuel line that comes with diesel heaters looks DIFFERENT than the fuel hose that people are used to seeing…

… so it’s easy to assume that it’s an inferior product.


This type of fuel line is specifically designed to work with diesel heater systems:

  1. It’s narrow diameter bore prevents air gaps from forming
  2. The rigidity stops the absorption of the fuel pulse from the pump

I nearly made the mistake of “upgrading” to automotive fuel hose…

Diesel Heater Installation Mistakes - Using the Wrong Fuel Line

Until I heard from someone who really knows what they’re talking about

[This legend made a 22 minute video going into the ins and outs of the fuel system]

Use the fuel line the diesel heater comes with… if you’re worried about sunlight or stone damage then cover it with some conduit.

5. Mounting the fuel filter after the fuel pump

The aperture in these fuel pumps is pretty small:

They can get clogged up pretty easily

[even a partial blockage will reduce your diesel heater’s performance]

Diesel Heater Installation Mistakes - Mounting Fuel Filter After Fuel Pump

So you want to make sure there’s no sediment getting into the fuel pump.

Mount the fuel filter before the fuel pump to prevent blockages.

6. Installing the fuel filter backwards

I assumed the little basket in the fuel filter was to catch any sediment.

The key word there?


These fuel filters are designed such that the fuel goes in AROUND the basket

Diesel Heater Installation Mistakes - Fuel Filter Installed Backwards

(otherwise the basket would fill up rather quickly)

Diesel Heater Fuel Filter - Direction of Flow

Mount the fuel filter so the diesel flows in and around the basket. Not into it.

7. Facing the air intake hose forwards

What’s the problem if the air filter is facing forwards?

When you’re driving there’s air, dirt, dust and bugs being pushed into the system at high pressure.

(especially if you don’t have an air filter on the end of it)

Incomplete combustion.

HINT: Some of the diesel heaters are sold with “silencers” that look pretty much like the air filters…

…but bench testing shows they increase the noise!

And they don’t filter. Which makes them useless.

Mount the air intake hose so it’s protected from air being forced into it while you’re driving. And make sure you have an air filter.

8. Installing the diesel heater without any base plate insulation

The fan in these heaters work really well to transfer the heat from the engine to the air ducts:

The base plates don’t get that hot during normal operation

How hot does the base plate of a diesel heater get

[this was after about 10 minutes on high]

But what happens in the unlikely event that power cuts out?

There’s no way to dissipate the motor’s heat.

Risk = Likelihood x Impact

Sure it’s unlikely… but the potential impact?

This one makes me sleep better at night:

Place some heat resistant silicon, a piece of concrete sheat, or a heat proof chopping board between the base plate and the floor.

9. Fitting the diesel fuel tank nozzle on the bottom

These bottom-mounted fuel tank nozzles are notorious for developing leaks.

Bottom-Mounting A Diesel Heater Fuel Tank Nozzle

And even if that doesn’t happen?

Diesel can be dirty.

If you’ve mounted the fuel tank nozzle on the bottom, you’re guaranteed to get sediment in your fuel lines.

Use a fuel standpipe that’s cut to allow a minimum of 25mm from the bottom… or at the very least side-mount the fuel tank nozzle.

Using a Fuel Standpipe for Diesel Heater Tank

[if your diesel heater doesn’t come with one, they’re less than $10 here on eBay]

UPDATE: Not only does installing a standpipe reduce the risk of spillage… this can provide the option of using a jerry can and using a quick disconnect!

Diese Heater Fuel Line Quick Disconnect - Before and After

ReadDiesel Heater Fuel Line Quick Disconnect: Installation and Review

10. Drilling a hole in the floor from the top down

If you’re using a hole saw and you only drill from the top down it chews up the wood underneath:

You now have unsealed and unprotected wood that’ll be exposed to the elements when you’re driving

Diesel Heater Installation Mistakes - Drilling a hole in the floor from the top down

It takes about two seconds to prevent this:

Start drilling the hole from the top, then finish it off from underneath (and use some sealant while you’re at it)

11. Starting the diesel heater for the first time without priming the fuel line

The fuel pump is only lubricated by the diesel itself.

When there’s no diesel?

There’s no lubrication.

And considering the fuel pump dose is a tiny 0.02 ml per stroke?

If you dry start your diesel heater that’s A LOT of metal on metal before the fuel pump gets its first sip of diesel.

Diesel Heater Fuel Filter Connected

[and if it hadn’t had a meltdown, it’d surely have some arthrits for the future]

Unfortunately this isn’t one of the reversible diesel heater installation mistakes.

Make sure you prime the fuel line before you connect the line between the fuel filter and the fuel pump.

12. Pointing the exhaust underneath the van

This one is more of an insurance policy:

These diesel heaters are very efficient and don’t produce much Carbon Monoxide.

But what if they’re not working properly due to:

  • Fuel pump not mounted correctly
  • Water caught in the exhaust
  • Just a plain old malfunction

Diesel Heater Installation Mistakes - Mounting Muffler On Side

Next thing you know… Carbon Monoxide trapped under the van.

Now this may never happen, but why take the risk?

Point the exhaust away from the van, not under it.

And if you’re going to ignore this, at least avoid…

Q13. Not installing a carbon monoxide alarm

To be honest:

I was tempted to leave this off this list of diesel heater installation mistakes…

…you shouldn’t actually need a CO monitor

[diesel heaters work by blowing the heat off the outside of a fully contained motor]

But here’s the thing:

Diesel heaters are fully sealed…until they’re not.

Diesel Heater Leaking Inside Cabin - But Is It Carbon Monoxide

Now, it is actually VERY difficult to find examples of these things leaking

(your main concern should actually be problems with the gas system)

Either way, for peace of mind we have one of these Carbon Monoxide detectors by Quell:

Best Carbon Monoxide Detector for Diesel Heater in Caravan

They’re about $45 here from eBay, or just pop down to Bunnings and get one (more like $60 there though)

Summary: diesel heater installation mistakes

So these are the most common diesel heater installation mistakes

(and oftern you see more than one in the same installation)

6 Diesel Heater Installation Mistakes - Same Installation

Hopefully you’re reading about these before you’ve started.

If not, the good news is that most of these are reversible.

To be honest:

Most of the feedback I’ve read hasn’t been due to diesel heater faults, but related to the installation. When done properly, they’re totally a great deal

(so this will be a good head start)

ReadGas vs Diesel Heaters: Pros, Cons, FAQs (and Myths)

Haven’t bought a diesel heater yet?

Here’s the eBay link to the one we bought (very happy with it)

Comment below if you have any questions. Otherwise, check out 33 Most Popular Caravan Accessories for Travelling Australia