Zeus-F3 Fuel Tank Heater

The Zeus-F3 is a heated fuel pickup — a diesel fuel tank heater that works at one point instead of everywhere. It mounts on the pickup tube, or standpipe, already in your tank and warms only the diesel being drawn up that tube — the one place where wax stops flow before anything downstream even sees it. A built-in slot filter screens coarse debris on the way in. It runs on 12V, draws up to 150W, and uses a self-regulating PTC element that cannot overheat your fuel.

• Voltage: 12V only (10.8–15V) — we do not build a 24V version
• Power: up to 150W, startup draw under 10A, 15A fuse supplied
• Element: self-regulating PTC — no thermostat to set, no runaway
• Fits: Ø0.39 in (10mm) pickup tubes up to 31.5 in (800mm) long
• Tank opening needed: 1.54 in (Ø39mm) minimum
• Sealing: IP68 inside the tank, IP67 outside
• Service life: 4,000+ hours / 3 years per the factory data sheet
• In the box: heater, 2 grooved gaskets, lock ring, relay, 15A fuse, dash button, LED, harness, manual

If a fresh filter did not fix it, the wax is at the pickup

Changing the filter and getting five more minutes of running is the classic symptom of wax sitting in the tank, not in the filter. Operators describe it the same way every winter: new filter, dose of anti-gel, engine runs briefly, dies again. Pull the line at the lift pump and slightly gelled fuel dribbles out; let it run clear and you get another five minutes.

Two things make the pickup the worst spot in the system:

• The pickup screen is a strainer sitting in the coldest fuel in the tank. Wax crystals collect on it and choke flow long before the tank is anywhere near solid.
• Additive you pour in the filler cannot reach fuel that has already waxed. Anti-gel works by keeping crystals from forming; once they have formed around the pickup, mixing more treatment into the top of the tank does not dissolve them.

That is where the Zeus-F3 sits. It does not wait for the problem to travel downstream.

Why 150W at the pickup beats a much bigger pad on the tank

A pad on the outside of the tank has to warm every gallon in it before the pickup feels any difference. On a 100-gallon saddle tank in a -4°F (-20°C) night, that is a large thermal mass, a lot of surface losing heat to airflow, and hours before anything changes at the intake.

The Zeus-F3 does the opposite. It only has to raise the temperature of the fuel actually moving up the tube — a thin stream, warmed at the exact moment it is drawn. The power number looks small because the target is small. That is the whole design idea: heat what leaves, not what sits.

It also means no shore power. Tank pads in this size class run on 110V or 230V and tie you to a plug; the Zeus-F3 runs off the vehicle battery through the supplied relay.

Specifications

Self-regulating PTC — what that actually does for you

As the PTC element warms, its own resistance rises and throttles the current back. It settles at its working temperature and stays there, on its own, with no thermostat, no sensor and no control box.

Inside a diesel tank that matters more than it would anywhere else. There is nothing to stick closed, nothing to calibrate, and no failure mode where a stuck contact keeps feeding power into a heating element sitting in fuel. The element is also built to be shock-resistant and rated for use in a fuel-vapor environment.

What it does not do is decide when to run. The Zeus-F3 is switched by hand from the dash — self-regulating is not the same as automatic. The safety rules below are yours to follow.

Wiring exits through the flange gasket — no drilling

The kit replaces your stock flange gasket with two grooved rubber gaskets, and the wires run out through the channel the two grooves form when they meet. No new hole in the tank, no hole in the sender plate.

This works on flange-and-bolt pickup units — the arrangement on most semi-trailers, tractors, construction machinery, gensets, buses and marine tanks. If your tank uses a lock-ring sender module, which is common on some North American light trucks and pickups, there is no separate flange gasket to swap and the wires have to get out another way. Tell us your tank arrangement before you order and we will say plainly whether this fits.

Installing it

1. Disconnect the battery. Remove the pickup or sender unit from the tank.
2. Slide the insulation sleeve onto the pickup tube, then push the heater onto the tube all the way to its stop. If you use a 1mm gasket, shorten the pickup tube by 0.16 in (4mm) so immersion depth stays correct.
3. Tighten the two set screws until their slots line up with the ring groove, then seat the lock ring in the groove so the screws cannot back out.
4. Route the wires through the groove channel between the two rubber gaskets and seal it. Leave about 6 in (150mm) of wire from the gasket to the plug; wrap the excess around the pickup tube over the insulation sleeve and tie it off. Never tie the wire in a way that could pull it out of the heater.
5. Refit the pickup into the tank.
6. Wire the cab side: battery positive → 15A fuse → relay → heater, negative to the vehicle body. Mount the push button and LED on the dash within reach — button cutout 0.80 in (Ø20.2mm) with a 2.2mm locating slot, LED bracket hole 0.26 in (Ø6.5mm). Relay and fuse go under the dash panel.

Running it through the winter

Press the dash button 3–5 minutes before you crank, then start. The LED tells you the element is drawing. Switch it off once the engine is running and fuel is moving.

Use it only in below-freezing weather, and only when pickup is actually difficult. This is not a device you leave on.

Safety rules — these are hard limits, not suggestions

This heater sits inside a diesel tank. Read these before the first cold morning, not during it.

• Diesel only. Never switch on with gasoline- or kerosene-blended fuel. If you winter-blend with kerosene, do not use the heater on that fuel.
• Never switch on with less than 0.79 in (20mm) of fuel in the tank. There is no dry-burn protection — confirming there is fuel over the element is your job.
• Do not switch on above freezing — 32°F (0°C).
• Install or remove the pickup only with the heater switched off and the battery disconnected.
• Diesel vapor is explosive. No open flame where fuel is handled; use explosion-proof lighting.

We publish these plainly because the alternative is worse. Every winter someone puts a torch on a frozen fuel line because nothing else is working — that is the situation this product exists to prevent, and it is not one to be casual about.

Maintenance

Clean the slot filter periodically with a blunt wooden stick — never a sharp metal tool. A scratched or deformed slot changes the intake geometry and can shed metal into the fuel. Check the electrical connections including the body ground point at the same service.

Where it earns its keep

Anywhere the machine sits outside overnight and has to start cold in the morning. Diesel gensets are the clearest case — a standby set that will not draw fuel is a standby set that failed. Beyond that: semis and trailers, agricultural tractors, construction machinery, buses, ambulances, boats and light commercial vans.

Most cold-climate fleets end up running the pickup and the filter together. See the whole range of fuel heaters for how the points fit together.

Frequently asked questions

I changed the fuel filter and it still stalls. Will this fix it?

If a fresh filter only buys you a few minutes of running, yes — that is exactly the pattern this solves. It means wax is still sitting in the tank around the pickup and in the suction line, so the new filter loads up again as soon as it starts drawing. Heating at the pickup keeps the fuel moving before it reaches the filter. Note the other suspects worth ruling out first: a collapsing suction hose, water freezing in the fuel, or a plugged pickup screen from bio growth all produce the same symptom.

Does it heat the whole tank?

No, and that is deliberate. It heats only the diesel being drawn up the pickup tube. Warming a full tank takes hours and a great deal more power; warming the stream on its way out takes 150W and 3–5 minutes. If what you actually want is a whole warm tank — a long shutdown in extreme cold, say — then you want a wrap-around fuel tank heater pad on shore power, not this.

Do I still need anti-gel additive?

Yes. Additive lowers the temperature at which wax forms throughout the tank; the heater keeps the one point that matters clear when the additive is not enough. They do different jobs. Dose the additive as you fuel so it mixes going in — treatment poured on top of already-waxed fuel does very little.

Can I run it with the engine off?

Yes — that is how it is meant to be used. Press the button 3–5 minutes before cranking, with the engine off. Just switch it off once the engine is running, and never leave it on unattended.

What happens if the fuel level drops below the heater?

Do not switch it on below 0.79 in (20mm) of fuel. There is no dry-burn protection. The PTC element limits its own temperature, but it is designed to shed heat into liquid fuel, and running it in vapor is outside what it is built for.

Is there a 24V version?

No — the Zeus-F3 is 12V only. There are 24V heated pickups in the wider product family, but we do not build one. If you are on a 24V system, tell us the application and we will tell you honestly whether we have anything for it.

Will it fit my tank?

Two measurements decide it. The pickup tube must be Ø0.39 in (10mm), and the tank opening must be at least 1.54 in (Ø39mm) — the heater body is 1.50 in (Ø38mm), so clearance is about 0.02 in (0.5mm) per side. Also check whether your tank uses a bolted flange or a lock-ring sender module; the no-drill wire exit depends on a flange gasket being there.

How long does the element last?

4,000+ hours of operation, and a 3-year service life, per the factory data sheet. In practice the heater only runs a few minutes per cold start, so that is a long time in service. Warranty is 12 months.

Can I use it with winter-blended fuel?

Not if the blend contains gasoline or kerosene. That is an absolute limit, not a caution. If you blend with kerosene for deep cold, run the blend without the heater, or use a different heating point in the system such as a filter heater.

Does the slot filter replace my fuel filter?

No. It is a coarse strainer that keeps debris out of the pickup, in the same role as the stock tank screen. Your primary filter and water separator still do their jobs and still need servicing on schedule.

Related: fuel heaters — how the tank, line, filter and separator heaters work together across a diesel fuel system.