Blower Motors

[jaydev]

Hi,

I was wondering if somebody could enlighten me on how the climate control operates.

During this heated period and great weather, I have been out in the cat and I was operating the Air-conditioning. It seems to blowing cold air ok so that seems all fine. However, I have noticed that there is a right hand blower fan and a left hand blower fan; I just wanted to compare the operations with somebody else’s XJS and see if my one is different.

Here goes, If I set the Temp to 65 deg F and have the fan set to low; the left hand blower (passenger side) goes on at low speed. Then I set the fan speed to Norm, and still the left hand blower (passenger side) rises in speed. The right hand (driver’s side) still remains off.
When I set the fan to High, then both Blower fans come on at high speed. But when the fan is set back to Norm then the right hand blower turns off.

There was a situation yesterday when I had the fan speed set to High for some considerable time, and when I returned it to Norm both fans still remained on but at a lower speed. Then I set the fan speed to low and the right hand blower (driver’s side) went off. I then switched it back to Norm and the right hand blower stayed off.

I have checked the two 25A fuses in both locations

Q. Should both Blowers work at all settings?

Many thanks.

Jay

PS it’s a RHD pre facelift

[dhdove]

Jay
As far as I know both fans should work in tandem, otherwise air gets blown back up the side of the "weak" fan. So some of the cold air driven from the L/H fan is emerging out of the bonnet intake!
I suspect that your R/H fan has a dodgy transistorised speed control. I think to rectify this you have to remove the fan unit complete and disassemble to replace, it's soldered in to the fan casing.
I haven't done this (R/H fan removal) but I believe it's more time consuming and awkward than difficult.
I can't advise on the required transistor unit but I'm sure someone else will post with further info.
Good Luck
DH Dove

[Jon]

Just to second what dh dove has said, it is likely to be a problem with the darlington transistor. Theres also a little diode that rots away, so its advisable to replace both.

The reason it works on high speed is that there is a high speed relay which bypasses the transistor control on high speed.

The following page may be helpful.

http://www.jag-lovers.org/xj-s/book/acblower.htm

If you don't fancy messing around soldering though, I think complete 2nd hand replacement assemblies are available fairly cheaply.

[jaydev]

Hi,

Thanks very much for the info.

Is the Fan Motor and assembly directly behind the main fuse box on the drivers side?

I know dh mentioned that it would be quite time consuming on removal but could some one kindly suggest where i start on taking things apart.

Many thanks once again

Regards

Jay

[dhdove]

Jay
Start in front of the driver's seat and keep going until you get to it!
DH Dove

[poprivet]

The following page may be helpful.
http://www.jag-lovers.org/xj-s/book/acblower.htm

Confession time. That web page is mine. It was based on a combination of my own findings, suggestions from the old Jag Lovers bulletin board and also wiring diagrams by our own MarkB.
The info is achived in JagLovers and on the 'Nine-Lives' CD rom. From the feedback I've received world-wide it's helped countless owners. The information is still valid if a little out dated, I hope it will help you analyse and repair the problem.
Pop

[Jon]

Hi,

could some one kindly suggest where i start on taking things apart.



One tip: when you've loosened off the fuse rail (I'm not sure if that is necessary but it makes things easier) pull down the recirculation flap on the bottom of the blower assembly and hook it down with a peg or something. This will close the fresh air flap on the top of the unit which you can't see very well, but it will make it easier to remove the assembly.

My assembly didnt seem to want to budge even with all the fixings off. If this happens to you, just persevere, it will come down eventually with enough gentle persuasion!

When it comes to refitting I suggest fitting the blue pipe back on the blower assembly first and securing it with some strong tape. If you don't, chances are you'll pull it off the blower when connecting it at the other end, and its impossible to re-fit it to the blower when its in situ (I couldn't do it anyway!! )

[jaydev]

Very many thanks for all your kind help, I will attempt to dismantle and inspect.

One thing I forgot to mention, im not sure but I think it started happening when i installed a new stereo. I did notice some connectors in the area which the stereo goes. I made sure that none of them were disturbed, but its really tight in there. so im not sure if somthing was disturbed there. But the point i mentioned above when I had the blower on high and then switched to low the right hand blower decreased in speed as it should so its possible that the circuit in the blower assembly might be intemittent.

What ever the case i will have a bash at it.

Many thanks to all

Regards


Jay

[Mark_B]

Judging by the symptoms it does look very much like a disssolved diode, rotten resistor and a dud darlington device, very common problem.

If you're going to replace the parts yourself you need to be already proficient with a soldering iron, and then giving the circuit board a good coat of varnish both sides afterwards.

Though having said that... an intermittent connection where the wires go into the ECU can cause these symptoms too, I've had this happen to me, but admittedly I'd unplugged the wires from the ECU about half a dozen times. If the wires are flexed too many times the wires can break inside the insulation rather like a vacuum cleaner flex always breaks inside the wire near the handle. If it's that then you'll find the right side blower starts and stops to order if you poke around the wiring going into the ECU with your finger. It might be worth trying that first.

Yes I ought to revamp my delanair website, it does look a bit dated !

[jaydev]

Morning Chaps,

I have managed to have a look under the steering wheel area rummidged around the ecu area. But nothing in the form of the motor working on low and norm. So, before i begin the dismantling the fuse box and brackets woud sombody know where the supply wires go in to the motor. before dismantling the assembly i just wanted to check that the motor is getting the volts from the ecu.


Many thanks.

Jay

[dodgy]

Hi Jaydev,

As discussed above, if the fan runs at full speed but not at any other setting than it is almost definatly the power module on the fan assembly. You will need to take out the whole unit and replace/repair it. There are some pictures of a 1995 XJS version which shows what it should look like here You should lubricate the fan while you are in there as it is not fun to get in/out. The fan assembly will not come out unless you open the recirculation flap as also mentioned. I spent ages trying to get it out until I moved the flap and then it was out in seconds.

best of luck

Dodgy

[Mark_B]

Supply current to motor is a fat pair of wires whcih connect via a 2-pronged black rubbery push-together connector. The wire supplies power if I remeber rightly straight from the battery via a fuse. Between these wires and the motor is a control 'darlington circuit' for low/med speed. Bypassing the darlington is the 'high speed' relay. Both the relay and darlington are controlled via thin wires from the ECU. THese control wires carry no power.

[jaydev]

Many thanks to you for the advice.

I will get on the case now, I think i will buy a Darlington Transistor and the other components before hand and replace what i can whilst the unit is out.

thank you very much

Jay

[Charlie99]

Hi All,

A slightly different problem but not sure if it could be the same cause.

I've had the car for about 10 months, used as a daily driver and the fans worked peferctly.

A couple of days ago I noticed that the fan speed seems to be 'hunting' fast and slow, changing quickly.

This happens no matter what setting - low, Norm, Max or defrost and only varies slightly when the temperature set point is changed.

There are no unusual noises so I don't think it is fan bearings or similar. I presume it is a problem with the speed control rather than temperature sensor since it also affects the Max & Defrost settings.

I still get hot air, it is mostly annoying at the moment but i'd like to get it sorted before something packs in completely.

Any suggestions greatly appreciated.

Thanks,

Keith.

[Mark_B]

this a strange one.. because when the RH knob set to Max or Def, both blower fans should be at flat-out speed as the high-speed overide relays are bypassing the 'darlington' speed control.

If the HS relays each side are working ok and the speeds are still fluctuating then it can only be something like the motor brushes worn making intermittent contact, getting worse.

Are you sure both blower speeds were changing together at same time? It only needs one side on the blink to cause air stopping and starting.