Parts for your 1988 Suzuki Jimny-Temperature sensors

1988 Suzuki Jimny (Sierra SJ413) temperature sensors — what they do and how to look after them

Temperature sensors are absolutely relevant and used on the 1988 Suzuki Jimny, known locally as the Sierra SJ413. Factory literature such as the Suzuki SJ413/Samurai workshop manuals, the Haynes Suzuki SJ410 & SJ413 manual, and the Gregory’s Suzuki Sierra manual describe a coolant temperature sender for the dash gauge on carburetted models, and, on fuel‑injected variants (mainly JDM), an engine coolant temperature (ECT) sensor for the ECU. Many models also use a thermo-switch for an electric radiator fan where fitted, though a lot of AU/NZ Sierras ran a mechanical viscous fan instead.

On this tough little 4x4, the temperature sensors do a few key jobs:

• Coolant temperature sender (single-wire) runs the dash gauge so the driver can monitor engine temperature.
• ECT sensor (two-wire, EFI models) tells the ECU how hot the engine is for fuelling and ignition decisions, especially on cold starts.
• Thermo-fan switch (where fitted) turns an electric radiator fan on and off at set temperatures.

Replacing or maintaining these bits is straightforward and worth doing when the gauge reads oddly, the fan won’t kick in (on electric-fan models), there are hard cold starts (EFI), or there are signs of overheating. Good service practice on a 1988 Jimny/Sierra includes:

1. Work with a cool engine. Crack the radiator cap only when there’s no pressure.
2. Drain a litre or so of coolant to sit below sensor height.
3. Unplug the connector or remove the single wire. Note wire position and condition.
4. Remove the sensor or switch with a deep socket. Catch any spilt coolant.
5. Check threads and sealing surfaces. If the manual calls for it, use a suitable thread sealant or washer, avoid overdoing PTFE tape. Tighten to the specified torque in the service manual.
6. Reconnect, top up with the correct coolant mix, and bleed air. Verify the gauge reads steadily, the fan (if electric) cycles properly, and there are no leaks.

Preventative tips that help sensors live a long life:

• Keep the cooling system clean, replace coolant at the intervals in the manual (commonly every 2 years).
• Inspect and clean earths and connectors, a dodgy ground can make the gauge wander.
• If the vehicle has a viscous fan (common in AU/NZ), check fan clutch condition, if it has an electric fan, test the thermo-switch occasionally with a simple hot-water test.
• Confirm you’re fitting the correct part: the gauge sender (carb) and ECT sensor (EFI) look similar but are not interchangeable.

Quality OEM or reputable aftermarket sensors are inexpensive insurance on an ageing but much-loved Jimny/Sierra.

Popular questions about 1988 Suzuki Jimny temperature sensors

Where is the temperature sensor on a 1988 Jimny/Sierra?
On carburetted SJ413s, the single-wire coolant temperature sender is usually on the cylinder head near the thermostat housing. If the vehicle has an electric radiator fan, the thermo-switch may be in the radiator tank or the thermostat housing. EFI variants use a two-pin ECT sensor near the thermostat housing.

How can an owner test a temperature sender or fan switch?
For the dash-gauge sender, measure resistance across the sender body and terminal at different temperatures (room temp vs. hot water) and compare to specs in the workshop manual. A thermo-fan switch should show continuity only above its switch-on temperature, dip it in heated water while monitoring with a multimeter. EFI ECT sensors are tested by checking resistance across the two pins versus temperature.

Does a 1988 Jimny have an electric radiator fan?
Many AU/NZ carburetted Sierras used a mechanical viscous fan, so they won’t have a thermo-fan switch. Some market variants and EFI or A/C-equipped models used an electric fan with a dedicated temperature switch.