Jaguar XJ40 Blower Motor Not Working
The XJ40 has two blowers, and the usual reason one stops is a cracked solder joint in its footwell fuse box, then the speed-control transistor (high only) and worn brushes. If both blowers die with the climate panel lamps, it's almost always the microswitch behind the fan speed knob. I'd start by pulling each blower fuse in turn to find the dead side, then put a test lamp on its brown/blue feed.
How bad is it · Safe to drive
Safe to drive — but the screen may not clear
Nothing mechanical is harmed, but without the blowers the windscreen mists in wet weather. A blower that blows its fuse or runs its fuses hot should be disconnected until it's fixed.
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.
Cracked solder joints in the footwell fuse box
Each blower is fed from its own side fuse box, and the joint behind the blower fuse sits where the stacked boards flex most. It cracks, and the box passes voltage but not current.
One or both blowers dead on every speed, a fuse that looks and tests good, no fuse-fail message. Mostly 1993–94 cars, but earlier boxes do it too, and condensation from blocked drains corrodes them.
Test lamp, not a meter, on the brown/blue wire at the blower plug — it should be live even with the key off. A meter can show 8–10 V there that collapses as soon as the motor loads it.
Pull the box (about ten minutes a side) and reflow the joints at the blower fuse and around it. If you can't reach them, run a new fused 20 A feed from the box's supply to the brown/blue wire.
Microswitch behind the fan speed knob
A cam on the fan speed knob closes a small microswitch that powers the whole climate panel and unit — Jaguar covered it in TSB 82-38. When it wears or fouls, the blowers, the panel lamps and the A/C clutch all go together.
Ignition on, fan knob off OFF: no Auto/Manual or other panel lamps, no blower on any speed, not even High or Defrost, and no compressor click. Often intermittent at first — dead for a few minutes, or back after a flick of the knob.
Take the panel out — ski-slope trim off, then it slides out like a radio — and bridge the switch's two terminals with a short wire. If the panel and blowers come alive, it's the switch. A meter that beeps across it doesn't clear it; it can fail only under load.
Contact cleaner through the gap where the nub moves buys time. The lasting cure is a new switch: Jaguar kit JLM11240, or a generic SPDT microswitch with the lever removed, held by #2-56 screws and nuts in place of the drilled-out rivets.
Speed-control Darlington transistor
A board inside each blower makes low and medium through a 2N6284 NPN Darlington; high has its own relay. A binding motor or dried heat paste kills the transistor.
That blower runs on high and defrost only, low and medium dead. A fully dead blower on every speed is not the transistor. A transistor that fails shorted does the opposite: the blower keeps running with the key out, until it dies.
On the bench, 12 V straight to the motor: if it runs, the board is next. Inspect the transistor's solder and the diodes and 68 ohm resistor around it. Its mounting screws carry its earth to the case, so clean them; a meter on diode test shows it open when blown and conducting both ways when shorted.
Fit a new 2N6284 or NTE251 with heat-conducting paste, resolder the board, replace any failed diode or resistor. Free and oil the motor first, or the new one goes the same way. Often the board needs only cleaning and its joints reflowing, with no new transistor.
Worn brushes, dirty commutator or a seized motor
The motors are open-frame and sit in the air stream. Brushes start losing contact at about half worn, and water from blocked drains corrodes the commutator or rusts the shaft solid. Damp rusts the brush springs, and arcing brushes are what overload the speed-control transistor.
Slow, intermittent or dead; a kick to the knee bolster brings it back; grinding before it stops; hot 20 A blower fuses or a fuse that blows on high.
Pull the blower and turn the cage by hand — it should spin freely. Check brush length and that the springs press them onto the commutator.
Clean the commutator with fine paper until bright, fit new brushes (power-tool or starter brushes filed to size), oil both bushings. Free a seized shaft with penetrating oil; don't separate the balanced cage.
Relays inside the blower housing
Each blower carries an isolation relay and a high-speed relay. The originals (Hella 4RA 003 510-34) have a diode across the coil; a replacement without one fails or damages the control.
Dead on every speed, or no high; relays that click but don't pass current; burnt or pitted contacts. Speeds that come and go: a transistor is either good or dead, so erratic behaviour points at relay contacts or a motor binding until it warms.
Bench-test each relay under load, not for continuity. You can reach them through the top flap without removing the blower on some cars. The diode inside a relay can itself short. On a replacement, check which way round the diode sits — the stripe goes to pin 86 — before blaming the new relay.
Clean the contacts, or fit 40 A relays with a 1N4007 diode across the coil, polarity checked.
No feed to the climate unit: the A/C and radio relay
On 1987–92 cars the panel and climate unit get their 12 V through the A/C and radio relay under the passenger dash; 1993–94 cars use relay module H instead. Lose that feed and the panel, both blowers and the radio die together.
Panel lamps and blowers dead and the radio silent too. A radio that shorts can take the shared fuse with it, sometimes with a whiff of smoke from behind the glovebox.
Look for 12 V going into the relay and coming out of it, then on the light green/orange wire at pin 1 of the upper 15-way white plug on the climate unit — that pin corrodes.
Replace the relay, or the fuse with the faulty radio unplugged, or clean and re-crimp the corroded pin. If the relay socket is empty, as it can be on a 1990 right-hand-drive car, fit the relay.
A loose plug or spade connector
The blower plugs and the heater unit multiplug sit behind the knee panels and get disturbed by any dash work. A spade inside the fan cage can work loose after a bump.
Failure right after other work under the dash; both blowers and the panel lamps out at once points to the multiplug on the heater unit.
Remove the knee panel and push every plug home; feel for a spade off its terminal inside the fan cage while the fan is energised. On 1988 cars the right blower's isolation relay signal (orange/black) and its earth (yellow/green) come through a separate 15-way plug at the climate unit; a loose plug with those two wires belongs there.
Reseat the plug or spade.
Water in the blower box
The evaporator drains clog with foam from the sound deadening, or the heater matrix leaks. The blower box fills, the motor seizes and the circuit shorts.
Wet front carpets, green stains, water rushing behind the console, a coolant smell or misted screen; a blower fuse that blows with the A/C on. Gurgling from behind the dash with the air conditioning on.
Find the drain tube each side of the tunnel under the carpet and blow up through it; check the duck-bill drain in the engine bay. Coolant level dropping means the matrix.
Clear and rejoin the drains, drill out the clogged entry hole, repair or replace the heater matrix, then dry and service the blower. Compressed air up the drain tubes clears them for about a year; the foam is only pushed aside and comes back. Don't cut the duck-bill to make it flow — it keeps engine fumes out of the cabin. A casing that holds water can be given a small drain hole.
A tired original motor or assembly
After decades, motor and board can both be past saving. A weak motor also lets the stronger side blow back through it.
Weak air even though both sides run; squealing; a motor drawing enough to blow its fuse.
Compare both sides by pulling one blower fuse at a time.
A used blower (any 1990–94 one fits with connector changes), a rebuilt assembly with a sealed motor, or a matched pair of substitute motors.
Relay module H (1993–94)
Relay module H (DBC10009, yellow base, under the passenger dash) switches the ignition feed to the radio, blowers, phone, seats and mirrors. Its joints crack and it drops them all together.
Radio and blowers cut out together for a while, then return; electric seats and mirrors dead at the same time.
If the radio and seats work, it isn't this. Tap the module with everything dead.
Resolder and clean the module, or fit a used one.
The climate control panel itself
Behind the knobs is a circuit board whose solder joints and tracks crack or corrode with age. If bridging the microswitch doesn't wake the panel while 12 V reaches it, look at the board.
Panel stays dark with the microswitch bridged or new.
Open the panel and look for dull, ringed solder joints and green corrosion on the tracks.
Resolder the board or bridge a corroded track with a wire link; otherwise fit a rebuilt or used panel — and keep the old one, a new microswitch makes it a spare.
The climate control unit
The Delanair unit sends each blower its own speed and enable signal. It's the last suspect, after power and the blowers themselves.
Every mode lamp lit at once, even with a new panel, and blowers on high only.
Check the unit's outputs against the wiring diagram; 12 V on a blower's trigger wire tests the relay path past the unit. If the panel lights and the relays click, the microswitch is fine; look for 12 V on the orange wire at pin 1 of the middle 15-way plug (AC3) and check the permanent earth on the A-post above the right-hand fuse box.
Replace the climate control unit.
A broken blower wheel
The plastic squirrel cage or its ring breaks up. Pieces can end up in the evaporator.
Loud, out of balance, or a fan that sticks.
Look at the cage with the blower out.
Replace motor and wheel together — shaft sizes differ — or refit the ring if it has only come off.
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.
Find out which blower is dead
There are two, one above each footwell, and they blow against each other. With one dead, the other's air escapes back through it, so the vents feel weak even though a fan is running. With the fan on, pull each blower fuse in turn and listen, or listen at the scuttle by each wiper.
freeNote which speeds work
High and defrost only: the speed-control board. Nothing on any speed: power, relays or motor. Panel lamps out as well: the fan switch or a plug.
freeTest the feed at the blower plug
The brown/blue wire is live all the time. Use a test lamp, which loads the circuit; a meter can read volts that vanish under load. The blower fuse is B4, 20 A, in each footwell box on 1992–93 cars and F3, 20 A, on 1988–89 panels — check your year on the fuse box page. No feed with a good fuse means the box's solder joints.
a test lampPanel lamps or radio dead too?
Ignition on, fan knob off OFF: the Auto/Manual lamps should light. Panel dark and neither blower running: bridge the microswitch behind the fan knob, then check the heater unit multiplug. Radio dead as well: the A/C and radio relay under the passenger dash on 1987–92 cars, relay module H on 1993–94 — seats and mirrors out too with the module.
freeTake the blower out and bench it
Knee bolster and panel off, two plugs, two 10 mm bolts on a long extension; the first time can take four or five hours. 12 V straight to the motor: if it runs, look at the relays and the Darlington; if not, the brushes and bearings. Refitting, slotting one mounting ear lets the housing swing in under its bolt.
free, but a long jobWhile it's out
Brushes, bushings, relay contacts, the crumbling flap foam and the condensate drains. Replace flap foam with foam, not heavier rubber.
cheap partsBuying a used blower
Sovereign and base-model blowers are the same part; connectors changed in 1991. An L or R stamp marks rotation, not side — the L unit fits the right.
used unitThe 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.
Circuit descriptions from the Jaguar fuse tables, 1993 edition. Drawing by jagaux.com from the factory electrical guide. Fuse layouts change between model years — read the legend on the lid of your own box before pulling anything.
Circuit descriptions from the Jaguar fuse tables, 1993 edition. Drawing by jagaux.com from the factory electrical guide. Fuse layouts change between model years — read the legend on the lid of your own box before pulling anything.
What it usually isn't
Don't spend money here first:
If none of this finds it:
On jagaux.com
- XJ6 (XJ40) fuse boxesWhich fuse feeds each blower — other years from the same page.
- Jaguar XJ40 FUSE 1 or FUSE 2 FAIL WarningIf the trip computer reports a fuse box as well.
- Jaguar XJ40 Radio Not Working or Cutting OutIf the radio cuts out together with the blowers.
- Jaguar XJ40 Air Conditioning ProblemsIf both blowers run but the air isn't cold.
- Jaguar XJ40 ABS and Brake Accumulator ProblemsIf ABS and BRAKE lights came on after the blower was out — the brake pump relays sit on its housing.
- Jaguar XJ40 Heater Not WorkingIf both blowers run but the air stays cold.
- 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.