Mechanics

MODELS HEATER BLOWS ONLY COLD AIR

2001 Jaguar Other

Heater problem
2001 Other Jaguar Models V8 Two Wheel Drive Automatic 120000 miles

Whether on Auto or if I manually raise the cabin temp on the heater it blows cold air. I have already checked the heater core by taking the top 2 hoses off and running the garden hose through it and it appears to flow both ways un-hindered. I can hear the baffle moving when I change the temp (a creeking noise). The only odd thing is that when the car is hot and the heater is on the hose on the right (looking from the front) coming out of the heater core is cold. That hose runs into a distribution block by the radiator. I tried to run water through that hose but it is blocked at the distribution block. It appears that there is some sort of thermostat or valve that it runs into. Could that be the issue?

I am freezing my ass off on the way to work.

Thanks.
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Tallan1976
October 21, 2008.



AUTOMATIC A/C-HEATER SYSTEMS -2001 Jaguar XJ8
Page 1 of 3

NOTE: Diagnostic Trouble Codes (DTC) can be retrieved using Jaguar Portable Diagnostic Unit (PDU) or a scan tool. If not available, A/C-heater control panel DTCs can be retrieved using on-board diagnosis incorporated in A/CCM. PDU diagnosis is more comprehensive than A/C-heater control panel diagnosis.

RETRIEVING DIAGNOSTIC TROUBLE CODES
System Self-Diagnostic Test
A/C-heater control panel display will flash repeatedly indicating a list of 2-digit numbers. See DIAGNOSTIC TROUBLE CODE DEFINITIONS table. This procedure must be completed in order, through one complete cycle: 1. Display Element Check
Turn ignition switch to OFF position. Simultaneously press and hold AUTO and RECIRC buttons. See Fig. 1. Turn ignition switch to ON position while holding buttons. All display elements should illuminate and segments will flash on and off. If any display elements or segments do not light, an A/C-heater control panel or light fault is indicated.
2. Display Stored Numeric Trouble Code(s)

Press AUTO button. A 2-digit trouble code will be displayed. Codes 11, 15 and 21, will cause audible beep and ER to be displayed. If zero appears, there are no stored trouble codes, wait 30 seconds to allow system self-test to finish. A trouble code followed by a beep indicates an active trouble code. A trouble code not followed by a beep indicates an inactive trouble code stored in memory.
3. Scroll Through Trouble Code(s)
Press face button to display stored trouble codes. A maximum of 5 trouble codes can be stored.
4. Clear Stored Trouble Code(s)
Simultaneously press face and " R" (heated rear screen) buttons. It may be necessary to press face and " R" buttons to clear each stored trouble code.
NOTE: Actuator codes are not system trouble codes. See ACTUATOR CHECK under TROUBLE SHOOTING.
5. Initiate Actuator Check Press RECIRC button to initiate actuator check. Actuator codes 20 through 27. Press fan to skip actuator check.
6. Exit System Self-Diagnostic Test

Press fan button to exit system self-diagnostic test. Press PUSH OFF button to restore normal

10/21/2008
AUTOMATIC A/C-HEATER SYSTEMS -2001 Jaguar XJ8
Page 2 of 3
operation.
DIAGNOSTIC TROUBLE CODE DEFINITIONS DTC (Panel DTC). (0) (1) Normal Operation P0335 (.) Engine Speed Input In-Vehicle Temperature Sensor In-Vehicle Temperature Sensor Ambient Temperature Sensor Ambient Temperature Sensor Solar Sensor Solar Sensor Component B1253 (11) B1257 (12) B1260 (21) B1250 (11) B1258 (21) B1254 (12)
B1262 (44)
(2) Defrost Servo Motor
B1263 (45)
(2) Center Vent Servo Motor
B1264 (46)
(2) Foot Servo Motor
B1265 (43)
(2) Cool Air By-Pass Servo Motor
B1266 (41)
(2) Left Fresh/Recirculated Air Servo Motor
B1267 (42)
(2) Right Fresh/Recirculated Air Servo Motor
B1268 (34)
(3) Defrost Vent Feedback Potentiometer
B1271 (34)
(3) Defrost Vent Feedback Potentiometer
B1272 (35)
(3) Center Vent Feedback Potentiometer
B1275 (35)
(3) Center Vent Feedback Potentiometer
B1276 (36)
(3) Foot Vent Feedback Potentiometer
B1279 (36)
(3) Foot Vent Feedback Potentiometer
B1280 (33)
(3) Cool Air By-Pass Feedback Potentiometer
B1283 (33)
(3) Cool Air By-Pass Feedback Potentiometer
B1284 (31) (3) Left Fresh/Recirculated Air Feedback Potentiometer B1287 (31) (3) Left Fresh/Recirculated Air Feedback Potentiometer B1288 (32) (3) Right Fresh/Recirculated Air Feedback Potentiometer B1291 (32) (3) Right Fresh/Recirculated Air Feedback Potentiometer B1292 (.) Battery Voltage Supply Through A/C Isolate Relay Battery Voltage Supply Through A/C Isolate Relay Sensor 5-Volt Reference Voltage Sensor 5-Volt Reference Voltage Sensor 5-Volt Reference Voltage Battery Voltage Supply Face Vent Differential Temperature Control Face Vent Differential Temperature Control Aspirator Motor Aspirator Motor B1294 (.) B1298 (.) B1355 (.) B1852 (24) B1856 (.) B1297 (.) B1849 (24) B1299 (.) B1853 (.)

10/21/2008
AUTOMATIC A/C-HEATER SYSTEMS -2001 Jaguar XJ8
Page 3 of 3
B1857 (.)
Ignition Switched (AUX/ON) Ground Signal
B1858 (23)
(4) Refrigerant Dual Pressure Switch
B1861 (23)
B1862 (22)
B1863 (.)
B1946 (13)
B1947 (13)
B1948 (14)
B1949 (14)
B1966 (15)
B1967 (15)
B1968 (.)
B1969 (.)
U1263 (.)
U1264 (.)
(1) When there are no DTCs, WAIT 30 seconds for system self-diagnostic test to finish.
(2) Check for an open or short in motor drive circuit, or a sticking/jammed motor flap.
(3) Open or short in potentiometer feed circuit. At times, motor may overrun and set additional codes. Cycling ignition on and off 2 or 3 times may correct problem.
(4) Temperatures less than 32 °F (0 °C) may set false trouble code due to low refrigerant pressure. Temperatures greater than 95 °F (35 °C) may set false trouble code due to temporary high refrigerant pressure.
(4) Refrigerant Dual Pressure Switch Compressor Lock Signal Sensor Signal Ground Evaporator Temperature Sensor Evaporator Temperature Sensor Coolant Temperature Sensor Signal Coolant Temperature Sensor Signal Heater Matrix Temperature Sensor Heater Matrix Temperature Sensor Heater Pump Compressor Clutch Circuit Control Panel Serial Communication Control Panel Serial Communication

10/21/2008
Test this way and look up the code(s).

Merlin2021
Oct 21, 2008.
When I change the air flow on the control panel it switches to which ever option I choose. I really don't think it is a valve problem, especially with the cold heater core hose. Will this test of the AC/Heating system diagnose if the coolant valve @ the distribution block near the radiator is opening, allowing flow of hot water through the heater core? I didn't see that on any of the codes. They all have to do with the valves and air flow.
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Tiny
Tallan1976
Oct 21, 2008.
The reason we run this is a process of elimination, so please run it and post any codes, I can look them up and go from there! Team work!

Merlin2021
Oct 21, 2008.
I have a 2000 XJ8 with the same problem. Will your diagnostic process work for the 2000 model, also?

Thank you.

Tiny
Drewcollier
Dec 22, 2008.
I have the same problem with cold air from the heater. Seemed to happen at the same time the fog lights stopped working. I have checked all the fuses, given the relays a tap and swapped them out. Found an article about water ingress in the alarm sounder blowing fuse 6 on RH fuse box under back seat which causes heater pump and fog lights to fail, but it checks out ok on my car so didn't help. Bought a used pump today and plugged it into the feed for the aux heat pump under bonnet but it doesnt seem to be getting power? I will try the self diagnostics tomorrow, but I havent noticed any errors on the speedo display. The flaps etc seem to be working, air flow moving around from floor to screen etc when selecting appropriate buttons - but air is always cold unless engine doing over 3000 revs (pressume extra pressure from fast running engine makes some hot water travel through heater matrix even if pump not running? - Does this indicate heater matrix is ok?)

Could I have missed a fuse box, is there a common failure point on related wiring looms etc?

I was thinking it might be the multiway valve under the bonnet, but as the second pump didnt fire up when plugged in I have gone back to assuming electrical fault. Would the pump run anyway with heating turned on or could some other sensor stop it recieving power?

This is driving me nutty, I don't want to pull the dash apart and replace an expensive climate ecu without checking everything else first.

Many thanks for any help, Paul

Tiny
Fazery
Feb 2, 2009.
Hi Paul,

Its the alarm sounder, it fills up with water and blows the foglamp fuse under the bonnet on the ns, this also stops voltage to the heater pump. Disconnect the sounder(nsf underneath between rad and engine, replace fuse (i think its no 3) if foglights and heater pump work it needs new sounder (£ 133.34 +vat).

Hope this helps James

Tiny
Premveh1
Feb 18, 2009.
Ok guys, thanks to all. It was the alarm sounder, and yes, once disconnected and fuse under bonnet replaced all is once again ok. I believe this alarm sounder is a backup unit, does that mean the car horns will still sound if alarm triggered?

Next problem, the heater control panel has two buttons which are not being illuminated when the lights are on. The buttons are for 'feet only' and 'demist (screen and feet)', and they are both working fine, just no backlight. Do they have bulbs that are changeable? Could it be something else.

Tiny
Fazery
Feb 21, 2009.
Excellent article well done, had the same problem no heat on local journeys but normal when on 3000 revs, changed fuse number 3 under bonnet and disconnected alarm sounder all sorted. Well done guys !

Tiny
Cjvh
Jan 2, 2012.

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