Before I write this procedure step by step, I would like to thanks a lot to Mr. JSeaman from other Jaguar forum from UK let me copy some steps of his procedures.
One day is too cold in winter season in North America, UK or hot day in summer time in Texas of US , when you turn on AC but no air blow out at all, I imagine how frustration you are because it happen to me.
When blowers motor stop working, no air blow out at all, We will think straight blower problem but there are many things relative this problem, I would like to suggess that we need to check other components what is easy to access and cheap replacement them first before taking a part blower motor becuase it's hard to access and long procedure to do that.
Here things we need to do first: Check fuses, check batter voltage, check micro switch....

Step 1 - To start with we need to remove the lower cover in the passenger footwell. There are 4 Philips screws holding this on, one on the far left (nearest the door) shown in the first picture, one slightly further in front of the vent and two more on the right hand side nearest the centre console

Step 2 - Once you've removed the 4 screws you should be able to ease the panel away gently (note the 2 red plugs which hold the trim in place so it will need to be pulled out directly towards the passenger seat)

 

Step 3 Remove the lower air box guides airflow temperature sensor.

 

Step 4 - Disconnect all the multiplug connection which are starting to get in the way, also disconnect vacuum line and then remove ECU.

90 XJ40 model:

 

Step 5 - You can now slide your extension bars up and remove the 10mm bolt holding the blower motor fan in place. I beleive there are total 2 bolts secure the motor in place. And final you can remove the motor out.

 

Step 6 - There are 5 clips around the fan unit which hold it together, ease these off with a flatblade screwdriver (and cover with your hand so they don't go springing off!).


Step 7 Remove 2 philips screws and rubber seal

Rubber seal

 

Step 7 - Open up the blower motor, you see 2 blue relays insite. This relays need to check replacement them if bad.

 

Step 8 - Those relay has a diot connected terminal 85 to 86 and The duty of diode is protected relay coil, it let high voltage, high current flows around cycling the coil thru diode when supply voltage between those terminals suddently cut off. So it may burn out some time and go to damage relay coil.

 

Step 9 - These relay is hard to find in auto part. There are some on ebay but used. I would not recommand to buy the used one. I would suggess you go any local auto part close to you and buy the one like this which I bought from Radio Shack and modify it

 

Step 10 - In order to modify the relay, you need to order diode. Here diodes which bought from Jameco Electronic, part#1N4148. You will need this diode for rebuild the ciruit board of blower motor also. So I would recommand buy this diode.

 

Step 10 - Take a look at closely the original relay circuit in step 8. Use solder iron to solder the diode 1N5401 between terminal 85 & 86 of standard relay. See the black standard relay had been modified with diode 1N5401 below. Don't bend the diode to the site what I did below because it will get stuck and will not fit the relay into blower motor what I did mistake. Bend the diode to oppisite site.

 

Step 11 - I heard many people complaint about darlington transistor in circuit board of blower motor go bad by the time with some reason like water leak in the motor... Once we take a part blower motor out, all the hard works has been done so far, I would recommand rebuild completely the main circuit of blower motor because all the electronic components supply for this circuit is very cheap.
Components list:
1/ Darlington transistor: 2N6284
2/ Diode : 1N5401
3/ diode : 1N4148
4/ Tatalium Polarize capacitor: 22uF 16v
5/ Resistor: 68 ohms 5% tolerance
6/ Ceramic capacitor: A1C/103M that mean 0.01uF ceramic capacitor
all these components you can buy fom Radio Shack or you can order from Jameco Electronic. Here is link:2N6284: ST MICRO: ICs & Semiconductors

 

Zenidial,

What is the part number on the relay you found at Radio Shack?

Do both relays need to be replaced with modified relay's?

Great write up!!!

 

Here is the main circuit board of blower motor.

 

Rob Evenson,

the part# 275-0001 at Radio Shack.
I would like to replace for both relays because the internal diode of original relay is going to be bad by time. Those original diode is very smaller and with more than 10years, so you never know what is going on? Since you pull out the blower motor, Why we don't put the new one for another 10 years.

 

Step 12 - Now, you need solder iron, solder wick for unsolder all old components, and then replace them all with new components.
Here is some pics for old corrosion transistor......
Before:



After:


Before :


After:

 

Step 13 - Don't forget to clean up all the dirt build up in motor fan, cacbon brush.... by use air compressor gun before you start re-install every things back. The procedure for re-instalation back is invert way you take a part. That's it. Good lucks to every one.

 

Zenidyle,

I've heard some forum members even rebuilt the brushed on the motors, did you do this, or were yours okay?

 

Rob,

Mine is half worn out, So I am good with that because those cacbon brush is from original manufactury and very last long more than 150K miles. Yes, you can rebuild those cacbon brush and you can look in Grainger here is link http://www.grainger.com/Grainger/wwg...121212232836:s they have whole bunch of kinds cacbon brush for DC motor. Those cacbon brush made in China and won't last long. I would suggess use the old one until completely worn out and then rebuild it with junk China.

 

I was able to get the blower motor out using your directions as a guide and for that I am very thankful. There was about a half of a liter of dirty water in the assembly. How did the water accumulate in there? How can I correct the problem? Should I just get another unit? Is this a common problem? I do not want to install new transitors diodes and resistors unless I am sure I can resolve the water accumulation issue. Thanks

 

The HVAC blowers in my '90 Majestic quit. I rebuilt the pcbs including the small pcb connected/powering (replaced the cap) to the motors.
I replaced all parts after having done considerable research to select the correct(?) parts using original relays. Installed the right side (passenger)
blower yesterday turned it on and nothing but a dull click (relay?). Any ideas on where I messed up? Cap I used on small board with coils is a 1.0u 250v ceramic.
Thank you for your help.
Roger