AC not working on 99 RR 4.6 HSE Newbie needs help

[pgallagher99]

This has been helpful before so here I am again. My 99 LR has the open book and exclamation point on the HVAC display. Occasionally when very hot, the air will kick on. It may stay on through seveal ignition on and offs, and then it stops again. It seems that while it is blasting hot air, if I close off all the vents, it may kick on again, or may not. I am assuming it is a temperature sensor in the cabin. I do not know where to look. Anyone have any thoughts that would help a newbie.

[Savannah Buzz]

For the sensor, from the RAVE manual:

In-car temperature sensor

The in-car temperature sensor provides the ATC ECU
with an input of interior air temperature. The sensor is
integrated into the inlet of an electric fan, which is
installed behind a grille in the centre of the fascia,
immediately below the clock. The fan runs
continuously, while the A/C system is on, to draw air

through the grille and across the sensor.

For the symbol:

Fault detected (handbook symbol).

For some of the other problem areas:

Control system

The control system operates the refrigerant system
and the control flaps in the heater unit to control the
temperature and distribution of air in the vehicle
interior. It also outputs signals to the fresh/
recirculated air servos and the blowers to control the
volume and source of inlet air. The control system
consists of:
An Air Temperature Control (ATC) ECU.
An in-car temperature sensor.
An ambient air temperature sensor.
An evaporator temperature sensor.
A heater coolant temperature sensor.
A sunlight sensor.
A dual pressure switch.

A single pressure switch.

Might be a good isea to have this free download on hand for diagnosis.. Or use the built-in backup system model number 260 - roll down two windows and drive 60..

[pgallagher99]

I appreciate the help. Can anyone get me started on how I begin removing the center console faci to gain access to the temp sensor?

[Savannah Buzz]

I don't know about your model, but the Disco's have a body repair manual in the RAVE as well as the workshop and electrical manuals. It may be in one of the other files you downloaded.

[atancreti]

It is really simple on the disco. However I found that the clock is a pain. To remove the center of the dash ( I think thats what your meaning) on the disco is 6 screws. 3 on the lower left, 3 on lower right. I bet yours is close to the same..

[rtonder]

The sensor gets cabin air from the grill under the clock. There's a fan back there that sucks in cabin air and pushes it over the sensor. Sometimes the fan gets plugged with crap, and sits and hums without pulling anything in. Blow it out with some canned air and see if that helps. If you're getting the book symbol on the heater control it usually means a sensor is failing to communicate with the rest of the heater control, or it could mean the heater control itself is hosed. I find the most common problem is the temp sensor on the heater hose that tells the goofy thing that the coolant is hot enough to heat the cabin. If the contact area for the sensor is corroded or loose, the heater control won't start in automatic and delivers a book symbol on the dash. That said, your problem might be similar in that the cabin sensor isn't communicating the right data.

[rtonder]

Also check to see if the wiring connector to the A/C compressor is pushed in all the way.

[LRScott]

One thing you can do to overide the fault in the mean time is set the temp on both sides to "Lo". Then at least you won't be frying in the thing.