Hello,
When turning on my heater using the left hand fan control I get what sounds like medium speed for a few seconds. The speed then drops to very, very low. I did replace the control panel with no effect, but it does seem to function. It is getting cold here around Seattle. Thanks for any ideas.

 

Usually it's the low speed that doesn't work correctly if the speed control circuitry (inside each blower) goes haywire ...There are two relays in each blower so it's possible that one could have failed, but VERY unlikely that both failed at the same time ...so in my mind this points to a pre-blower fault, most likely in the control panel (but you replaced that ...)

Other possible scenario is that you've been living with one non-working blower for some time and now the other side has a problem?

Try to test each one individually by pulling the left and right fuses one at a time and see what you come up with - If one side isn't working, at least we'll have somewhere to start ..

Good luck and BTW my first winter I had no blowers at all and had to do the speed limit to get warm ...


addl: Did you ever reflow those fuse boxes as Rob suggested last year?


Larry

 

No, I have not been able to solder the fuse panels. Too much else to do on this car. Is it strange that after a few seconds the fan speed drops? Could it be vacumm doors?

 

Time for me to chime in. Do you have it set to manual or auto. If its on auto then it may well change speeds without warning. Just putting it out there....

 

Well, wether in manual or auto the fan control knob has no effect. Just a very faint blower sound remains.

 

Hi dbeck54,

Larry's suggestion to test for blower fan operation is the first thing I would do. It's likely that one of your blower fans has not been working and the other is now misbehaving for some reason.

Just to throw out a few other possibilities:

It may be possible that one of the temperature sensors has failed and is telling the climate control microprocessor that your fans should run on the lowest speed possible. Do the fans behave the same way if you set the system to A/C?

Another possibility could be that one of your blower fans is not working, and for some reason the other fan is running briefly then shutting off, and the very faint blower fan sound you hear is the aspirator fan on the internal temperature sensor behind the pepper shaker/pepper pot vent below the front passenger knee bolster or scuttle.

There have been a few reports of looseness of or corrosion on one of the electrical connectors on the climate control microprocessor, which is mounted on the right side of the Climate Control Unit (CCU).

If I recall correctly, you have the three humidity settings on your control panel. Be sure all those lights are off while testing the system.

There is a lot of information about the system in the XJ40 eBook at the Jag-Lovers forum. You have to join to view the eBook, but it's free, and there is a mountain of XJ40 information in the archives there.

Please keep us informed.

Cheers,

Don