Jaguar XJ6 (X300) Air Conditioning Problems
On the X300 warm air is usually a low charge with code 23 — the gas seeps out, most often through a condenser corroded at its lower mounts. I'd read the climate codes and watch whether the compressor hub turns before buying anything. After that: the clutch, the trinary switch, the condenser fans and a heater valve stuck open.
How bad is it · Safe to drive
Safe to drive — switch the A/C off if the compressor grinds or smokes
Warm air doesn't affect how the car drives. A grinding clutch bearing or a noisy compressor should be left switched off until it's fixed, before it seizes and spreads metal through the system.
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.
Low on gas from a slow leak — code 23
Every X300 left the factory on R134a, and the charge seeps away a little at a time — through the condenser, hose joints, service valves and the compressor seal. The low-pressure side of the trinary switch then stops the clutch, so the compressor simply never starts.
Cooling fades over a season, worst in traffic and on hot days, then warm air. The self-test shows code 23, sometimes 22. With the A/C on, the clutch hub stays still. There is no sight glass on this car. Early on it still cools first thing from a cool garage and loses ground once the car has stood in the sun.
Run the climate self-test first. Then gauges at about 1500 rpm: around 35 psi low side and 190–200 psi high side at 25 C, rising with heat. The charge figure is on a label at the top of the right-hand wing (under the front of the bonnet on US cars). If the fuse is good and the clutch stays out, suspect the charge before the wiring: the low-pressure side of the switch won't let it in. A vacuum that holds for half an hour also proves the system tight. The low-side port is on the pipe running up the right-hand side to the expansion valve; a DIY kit coupler fits only that one.
Find the leak, then have the system vacuumed and filled by weight: 1100 g ± 50 g of R134a with PAG 46 oil. A top-up can on a nearly full system works if the loss is slow, but a vacuum is the only way to get air and moisture out.
A leaking condenser — corroded at the lower mounts or holed by a stone
The condenser sits in front of the radiator on rubber upper and foam lower bushes. The lower bushes crumble, the thin aluminium touches the steel cradle and corrodes, or the core rubs through. Stones from the grille do the rest. The 4.0 and the V12 use different condensers, and the X300 part fits 1995–97 cars only.
Gas lost again within days or weeks of a regas. Bright green oily residue or dye on the bottom of the condenser or the undertray below it. A replacement that leaks again within a year or two is usually a bare aluminium copy meant to be painted, or one cracked in manufacture.
Take off the plate over the radiator (about 11 Torx screws, usually seized) and look at the bottom edge with a UV lamp after a dye charge. The lower bushes can be reached through the lower air intake in the bumper cover with the horizontal trim strip off, without opening the pipes; missing lower bushes also cause a rattle at the front.
Replace, don't repair — the tubes are too thin to hold a patch. A quality copy condenser does the job at a fraction of the genuine price. Fit a new drier and all four mounting bushes with it, then vacuum and charge by weight. It comes out from the top without removing the radiator. Buy a coated condenser — a condenser supplied with its drier under MNA-7390-AA fitted exactly where several copies didn't.
The compressor clutch — seized pulley bearing or burnt coil
The pulley spins on its own bearing whenever the engine runs. When that bearing dries out it drags, overheats the clutch coil and can melt the plate; a damaged coil then blows its 10 A fuse.
Rattle or grinding from the front of the compressor, grease flung around it, smoke from the clutch, or the A/C clutch fuse in the right-hand engine-bay fuse box blowing. The clutch clicks but the hub doesn't turn.
Belt off: the pulley should spin freely and quietly, and the centre hub turn smoothly against compression. If the hub turns and the pulley grinds, it's the bearing, not the compressor.
Change the pulley bearing — it can be done on the car with the clutch nut, plate and circlips off — or swap the complete clutch. A blown clutch fuse doesn't mean the compressor is finished.
The trinary pressure switch or a broken wire at it
The four-wire switch on the high-pressure pipe at the right-hand side of the bulkhead stops the clutch on low or very high pressure and switches the fans. Its contacts and solder joints fail, giving code 23 with a full charge.
The A/C dies suddenly rather than fading; code 23 although the gauges are normal; the clutch clicks in when the switch or its wires are moved.
First confirm there is more than 2 bar in the system — below that the switch is right to stay open. Then briefly bridge Blue/Black to Black at its connector: if the clutch pulls in and 23 clears, it's the switch. Never leave the bridge in. Two switches are listed for these cars — two-wire LNA7655BA and four-wire LNA7657AB — after a factory change to the pressure switches and fan control; fit the one your harness takes.
Resolder a broken or dry joint on its leads — no need to open the system. If the switch itself has failed, replace it.
The compressor itself — failed inside or seized
The X300 uses a Nippondenso 10PA17C. Run short of oil or gas it wears, and when it breaks up it sends metal through the condenser, drier and expansion valve.
A whine or rasp only while the compressor is engaged, getting worse; then hot air. The pulley turns with the belt but the hub stays still, or the hub can't be turned by hand at all. A rasp above about 2,500 rpm, only while the compressor works hard, has turned out to be a swash-plate thrust bearing fused to its washer. A rumble straight after a recommission with new parts often means too much oil, which can break the reed valves.
With the belt off, the hub should turn smoothly against compression. Look for metal at the outlet when the lines come off.
A remanufactured compressor with the correct oil in it, a new drier, and the lines flushed or replaced. A noisy compressor caught before it seizes costs far less. Drain the old unit and put the same amount of oil in the new one. After an overfill, recover the gas, drain the compressor, blow the lines through with nitrogen and refill with the minimum oil.
The condenser fans not running with the A/C on
Selecting A/C should bring both radiator fans in at low speed. Without air through the condenser the high-side pressure climbs and the switch cuts the compressor.
Cold on the move, warm at idle and in traffic, and slow to cool until the engine is warm.
Engine running, A/C on cold: both fans should run. Tapping the two-wire switch that briefly starts them points at that switch. Gauges at idle on a hot day: around 300 psi on the high side points at a dirty condenser rather than the gas.
Replace the two-wire fan switch; bridging its two wires gets the fans running at low speed in the meantime. Cleaning the radiator and condenser fins has brought idle cooling back on its own.
The heater valve stuck open
The A/C cools the air and the heater matrix warms it again behind the evaporator. A heater valve stuck open lets hot coolant through all the time, so the refrigeration works but the air comes out warm.
The suction pipe to the compressor is cold and the discharge pipe too hot to hold, but the vents blow warm.
Pinch both heater hoses with hose clamps and run the A/C. If the air goes cold, it's the valve, not the gas.
A new heater control valve. It saves a dash-out search for a blend servo.
A leaking hose, union O-ring or service valve
The flexible hoses perish and a hose that lies against the exhaust manifold burns through. Union O-rings and the service valves seep too. A loss spread over months is rarely the condenser or another hard part — a hole there empties the system in hours or days; look at the service valves, the O-rings and the compressor front seal.
A hiss when the hose is touched; oil wetness at a union; gas escaping from a service port while it's being filled.
Feel and look along each hose, especially near the manifold and the line beside the radiator. A sniffer or dye finds the slower ones. A damp service port is the valve core, not the cap — the cap only keeps dirt out, and an over-tightened one can push the core in. Sniffers give false alarms in moving air near the vents and can wrongly condemn the evaporator.
A hydraulic-hose shop can splice or rebuild the hose for much less than a new one. The service valves are cartridges that unscrew whole from the pipe — evacuate first, then fit new ones with fresh O-rings. Replace the O-ring at a weeping union. Seized unions on the drier: hold the hex on the drier with one spanner while turning the pipe nut with another; soak overnight first.
The outside-air temperature sensor open or missing
With no reading from the ambient sensor the climate control thinks it's freezing outside and pushes heat on every restart until the in-car sensor takes over.
Hot air for a minute or more after a restart on a hot day, then slow cooling. The EXT display shows two dashes or something far too cold.
Press the exterior temperature button and compare it with the real outside temperature. The sensor should read about 3.1–3.7 k at 10 C, 1.6–1.8 k at 25 C and 500–700 ohms at 50 C.
Fit a new sensor. A 1 k–2.2 k resistor in its place proves the point at once and stops the hot blast.
The A/C belt and its plastic tensioner pulley
The compressor has its own belt with a small plastic idler. The bearing in that pulley wears and the belt grooves the plastic; the square adjuster under the compressor rusts solid.
A whirring that follows engine speed with the A/C on or off; a screech, burning rubber or a broken belt.
Belt off, spin the idler: it should turn smoothly with no play.
Replace the pulley — a steel one with a replaceable 6203 2RS bearing outlasts the plastic original. To slacken the belt, loosen the pulley through-bolt first, then turn the square adjuster from below; soak a seized one in penetrating oil overnight.
The expansion valve blocked by beads from the drier
The receiver-drier sits on top of the condenser. When its desiccant bag tears, the beads travel to the expansion valve on the evaporator and choke it.
The discharge pipe very hot and the return pipe at air temperature; the low side reads very low and the clutch never cycles. A tap at the bulkhead sometimes brings the cold back for a while.
Gauges show the restriction. Before going further, open the old drier and see whether its bag has come apart.
On one X300 that a shop had booked for a new expansion valve, the beads were the whole story: dealing with the drier and clearing the beads brought ice-cold air back, and the dash never came out. So a new drier and the beads blown out backwards through the evaporator with nitrogen come first. The valve is not sold apart from the evaporator, and getting at it means taking the dash out.
Too much gas after a top-up
An overfilled system runs very high pressures on a hot day. The switch first runs the fans flat out, then cuts the compressor.
Poor cooling after someone added cans without gauges; the compressor dropping in and out more than usual.
Two-gauge readings against the ambient temperature.
Recover the gas and charge the exact weight from the label. Worth doing before suspecting anything dearer.
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.
Read the climate codes
Engine warm, switch off, then hold AUTO and RECIRC while you restart. AUTO shows the codes (0 means none) and DEMIST steps through them. 23 is the refrigerant pressure switch circuit, 22 compressor lock, 12 the outside-air sensor, 11 the in-car sensor fan.
freeIs the compressor turning?
A/C on, coldest setting: watch the centre hub, not the pulley. The idle dips a little when it pulls in. Clicking in and out every few seconds is normal.
freeFeel the pipes and watch the fans
The suction pipe should be cold and sweating, the discharge pipe hot. Both radiator fans should run with the A/C on.
freeClutch not pulling in? Pressure, switch, fuse
With more than 2 bar in the system, look at the trinary switch and its wires at the bulkhead. Then the A/C clutch fuse in the right-hand engine-bay fuse box, the clutch relay, and 12 V straight to the clutch for a moment.
freePinch the heater hoses
If clamping both heater hoses makes the air cold, the heater valve is letting hot water through.
freeFind the leak
UV dye or a sniffer. Start at the bottom of the condenser, then the hoses near the exhaust, the unions and the service valves.
a dye chargeRepair, then vacuum and charge by weight
New drier whenever the system has been open, new O-rings, a vacuum of 30–45 minutes that holds, then 1100 g of R134a with PAG 46. No stop-leak, no oil-filled cans.
about £60–80 for the regasOnly then the compressor or the expansion valve
When the gauges point at a restriction or the compressor won't pump with a correct charge.
a compressor, or the dash outThe 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, 1995 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
- Jaguar XJ6 (X300) Heater Not WorkingIf the problem is the other way round — no heat with the heat on full.
- Jaguar XJ6 (X300) Battery Drain, Flat BatteryIf the radiator fans keep running with the key out — the A/C pressure switch can do that.
- Jaguar XJ6 (X300) Alternator Not ChargingIf a belt squeal comes with the charge warning as well.
- XJ6 (X300) fuse boxes and relaysWhere the A/C clutch fuse in the right-hand engine-bay box sits; 1996 and 1997 from the same page.
- Jaguar XJ6 (X300) Overheating, Cooling FansIf the engine runs hot in traffic with the A/C on — the cooling fans may not be running.
- Jaguar XJ6 (X300) Suspension Knock, Rear ShocksIf the A/C stopped cooling after a knock from the front — a loose radiator can rub through the A/C pipe, see the suspension knock page.
- Jaguar XJ6 (X300) Climate Control Not WorkingIf the climate panel shows Er, stored codes or nothing at all.
- 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.