Jaguar XJ6 Series 3 Blower Motor Not Working
When both blowers on a Series 3 stop together, it's almost always the supply, not the motors: the 50 A fan fuse or its holder, then the climate feed fuses, an earth or the four-relay pack. I'd select Defrost with the engine warm first, then fit a new fan fuse and squeeze its clips before buying anything.
How bad is it · Safe to drive
Safe to drive — keep the screen clear
Nothing here harms the engine. Without the fans the screen mists quickly in cold or wet weather, and only ram air at speed will clear it.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
The 50 A fan fuse and its holder
Both blowers run from one 50 A fuse — fuse 16 in the auxiliary fuse panel on the 1987 layout. Lucas glass fuses break inside the cap or at a soldered end and still look good, and the cradle clips loosen, heat up and burn the wires behind them.
Both fans dead on every setting while the flaps and servo can still be heard moving; fans that come back when the fuse is touched. Fans that quit after driving through deep water, or that come and go before dying, point at the clips.
Don't trust your eyes or an ohmmeter: fit a new fuse, squeeze the cradle clips so they grip, then check 12 V on both sides with a test lamp under load. Drop the holder and look at the wires behind it. If the wires behind the cradle have overheated, they barely make contact even with a new fuse in place.
A new fuse and clean, tight clips. A scorched holder or a loose wire behind it is soldered or rewired; a thin-wire in-line bodge is replaced with proper cable. To keep the cradle, take it apart, solder the crimped wire ends and tin the contact faces. Don't split the load across two smaller fuses in parallel: they never share the current, and one ends up carrying it all unprotected.
Fans held off because the water at the heater is cold
When heating, a temperature switch on the heater inlet pipe keeps the fans off until the coolant reaches about 41 °C; Defrost overrides it. If the vacuum heater valve sticks shut, or air sits in the heater core, that pipe never warms and the fans stay off or blow cold.
Fans run in Defrost but not in Lo or Auto, or only once the engine is fully hot; the heater hose from the bulkhead stays cool.
Feel both heater hoses at the bulkhead with the engine hot. Pull the vacuum line and move the valve lever by hand. To prove the switch, unplug it and bridge its two wires — as a test only.
Free a sticking valve with penetrating oil and work it, or fit a new one. After a coolant change, with the engine warm and the front raised, hold the valve shut by hand for about ten seconds and let go to clear the air.
The climate feed fuses, hidden in-line fuses and earths
The relays, mode switch and amplifier take their own smaller feed, and in-line fuses hide behind the console side panels and knee ducts. With that feed gone the system acts as if it were switched off, even with a good 50 A fuse. A corroded earth does the same, or keeps blowing the fan fuse.
No relay clicks at all; the fans run when a relay is pressed by hand; fans and servo dead together. A feed fuse that blows the instant it's replaced points to a short in the sensor wiring rather than the fans.
Measure both sides of every fuse in both footwell panels, then look behind the console side panels and knee ducts for in-line holders gone green. Clean the earth points in the footwells. If it blows at once, unplug the wire at the in-car temperature sensor: a chafed white/blue wire between the in-car and ambient sensors can short to earth.
Renew the blown feed fuse, clean the corroded in-line holder, sand and grease the earth.
The four-relay fan pack
Fan speeds come from a pack of four relays (C46179) and a dropper resistor unit, low on the left of the climate unit behind the console side panel. A dead relay usually costs one or two speeds rather than all of them; a stuck one keeps the fans running.
Lo and Auto dead but Hi and Defrost fine, or low speed only whatever the setting; a click or a spark at the pack connector. Fans that keep running with the switch at Off, or with the key out, are usually a relay in the pack stuck closed: the motor feed is live all the time and only the relays switch it.
Test lamp on the heavy brown/white feed at the pack. With the ignition on and the switch at Hi or Defrost, jumper brown/white to green/slate: the fans should run flat out. In Auto at 65, wiggle and tap each wire at the pack. For fans that won't stop, pull the yellow, blue and red wires at the pack one at a time and see which stops them. Some cars have three relays in the pack and a separate round Low relay behind it, which fails regularly.
Clean and tighten the pack connector, restore a missing earth to the Hi relay, or fit a refurbished pack. A metal relay pack can be opened and its points cleaned; a plastic one is replaced.
A microswitch in the mode switch
The Off, Lo, Auto, Hi and Defrost positions work through small microswitches on a cam (AEU 2743). A cracked or sticking microswitch leaves the fans dead in every position, or running when they should stop.
No relay clicks in any position although the feed reaches the switch; fans that start only when the knob is rocked. A sticking Off microswitch can also leave the fans running at low speed with the switch at Off while every other position works.
Confirm power at the switch feed first, then at each microswitch output with the switch assembled.
Replace the microswitch (RTC675) or the whole switch panel with a good used one. It means dash work: photograph everything and mind the fibre-optic strands. Short of dash removal, a sticking microswitch can sometimes be freed with a long screwdriver from the right footwell and a shot of PTFE spray — a temporary cure.
The climate amplifier and its setting
In Auto the fan speed follows the amplifier and servo; Defrost and manual Hi bypass them. An amplifier set too far one way can hold the fans at a quarter speed, and a failing one leaves only Defrost working.
Speed doesn't change with the temperature knob while Defrost runs flat out; no servo sound when the knob is flicked.
With the cabin between 65 and 85 °F, flick the knob between 65 and 85 and listen for the servo each time. The adjustment screw is fine-tuning only — turn it in small steps.
Turn the adjustment screw clockwise; if the servo won't respond, try a known-good amplifier. The original amplifier is a common failure; a replacement unit is the reliable cure.
The fuse keeps blowing or the fans won't stop
A new fan fuse that blows at once points to a short or a burnt motor, not the amplifier. Wiring from an added auxiliary cooling-fan circuit can feed back into the climate circuit and blow its fuse; a broken wire at a fan touching metal keeps it running.
The fuse goes straight away; fans run with the switch off; trouble began after electrical work. On a car with the auxiliary radiator fan, a shorted isolating diode on the small board near that fan can keep the blowers running at low speed.
Disconnect the motor wiring and reconnect one at a time. Check any added fan wiring for crossed wires, and the small wires at each fan housing for chafing.
Correct the crossed or chafed wire, then fit a new fuse.
A blower motor itself
There are two blowers, one each side, so both rarely die at once. One weak or dead motor shows as poor flow from one side; worn brushes are a known cause. On the 1987–92 V12 with Delanair Mk III, each fan has its own electronics in the housing, and water from blocked drains can kill them.
Air from one side only; on Mk III, fans stuck on high or never switching off.
Feed 12 V straight to a motor to split a fan fault from a supply fault. Where each blower has its own fuse, pull one at a time with the switch on Hi and listen. One dead fan is usually local to that side; both dead together send you back to the fuse, relays and resistor unit.
Worth trying: new brushes or a good used motor; on Mk III, a known-good fan unit. On a Mk III fan board, check the small diode as well as the Darlington transistor.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Engine warm, select Defrost
Defrost runs the fans flat out and bypasses the water switch and the amplifier. If they run here, the supply is fine — look at the heater water and the settings.
freeFit a new 50 A fan fuse
Fuse 16 in the auxiliary panel on the 1987 layout. Squeeze the cradle clips and test both sides with a lamp, not a meter.
a fuseCheck the feed fuses and earths
Both footwell fuse panels, the in-line fuses behind the console side panels and knee ducts, and the earth points.
a test lampProve the fans at the relay pack
Brown/white should be live. Jumper it to green/slate with the switch on Hi: if the fans run, the motors are fine.
a jumper wireWiggle the relay pack in Auto at 65
Tap the pack and move each wire with the engine running; a speed that comes and goes is the connector or a relay.
freeMode switch, amplifier, motors
Only after the above. The switch needs the dash apart; the amplifier is best tested by swapping in a known-good one.
parts plus dash workThe fuses named above — where they sit
The highlighted position is the one the procedure talks about. Pulling a fuse is a stop-gap, never a repair: check what the circuit feeds before you pull it.
We have no drawing of this box for this car — find them on the legend printed on the lid of the box itself.
What it usually isn't
Don't spend money here first:
On jagaux.com
- Jaguar XJ6 Series 3 Air Conditioning ProblemsIf the fans run but the air won't cool — the compressor clutch, the gas and the heater valve.
- XJ6 Series 3 fuse boxesWhere the main and auxiliary fuse panels sit, and fuse 16 for the blowers.
- Jaguar XJ6 Series 3 Heater Not WorkingIf the fans run but the air stays cold — the heater valve, the amplifier and the servo fuses.
- Jaguar VIN decoderConfirm your exact model year, engine and factory options before ordering parts — free.
Ratings, fuse numbers and torque figures vary by model year and market. Read the legend on your own car before pulling anything, and use the figures in the manual for your car, not the ones in a video.
Check your VIN: exactly which car you have and which bulletins apply to it.