Noisy blower

[Max]

How loud should the blower be? Mine is pretty noisy, much louder than the engine, making a rough mechanical noise as well as rushing air. Also doesn't work on speed setting 1. I'd like to do something about it, but it sounds like a nightmare of complexity in that system!

[almcl]

There are two blower motors and while you can certainly hear them on the higher speed settings, they shouldn't be excessively loud.

More info depends on what year your car is as there were several different systems used over time and how the speed is regulated varies.

[Max]

Yes, I realise there are two blowers, but couldn't be bothered to go back and change what I'd written! Mine's a '95 4L coupe, not a celebration. The whole ventilation system seems pretty weird, really, as everyone knows. For instance, if you press the "manual" button, what exactly is it that you can manually control???

[almcl]

Well past my knowledge level now, but manual should allow control of temperature.

In auto mode the system tries to maintain an in-car temp. In manual it blows air at the specified temp regardless of inside conditions.

If all is working well, selecting manual and min temp should result in air below 5C coming from the centre vent.

But as have never worked on anything past '93 there are almost certainly little differences...

Fan speed in the later cars should be continuously variable and once things have settled down in auto should drop to a steady low-ish speed.

[ptjs1]

Max,

All post-April 94 XJSs use the same aircon system.

In Auto mode, ie if "Manual" is not selected, Position "1" is a low-speed but variable fan speed. Position "2" is a fully variable speed. Position "3" is a constant maximum fan speed. Position "Defrost" is maximum fan speed at maximum available temperature. For all fan speed positions, the temperature is thermostatically controlled to the set temperature based on inputs from the cabin temperature sensor.

If "Manual" is selected, then Positions "1" & "2" stay at constant low and medium fan speeds respectively. In addition, the temperature selected is not thermostatically controlled.

A an over-enthusiastic fan speed, often on one blower only, particularly when Position 1 is selected is often indicative of a failed Darlington transistor.

Hope that helps.

Paul

[Max]

I'm sure it will help enormously, Paul, as long as I can remember it!

[ptjs1]

Max,

Put it in Auto mode, ie Manual button not lit, put the fan on Position 2 and just set the temp where you want it. Press the A/C button if you want aircon. Most owners leave it like this in normal running.

As the cabin reaches the thermostatically set temp, the fans will lower their speed. If they don't then you possibly have a darlington transistor failure. Plenty of info on that here on the Bulletin Board. Al is the expert on changing these!

Paul