Recently whenever I turn on my Climate Control the Blower motors may fail to turn on in any of the modes or work flawlessly.
Sometimes if I turn it to 'LOW' nothing happens. I turn it to "AUTO" "HIGH" and "DEFROST" and it works.
Sometimes if I turn it to "LOW" it works. I turn it to "AUTO" "HIGH" and "DEFROST" and it doesn't work.
Sometimes it will only work in "DEFROST" mode.
Sometimes it does not work at all.
When I turn the temperature switch, I hear the servos whirring so I know that part of the system works because whenever the blower motors feel to turn 'ON' the system operates as it should. I turn the temperature switch from 65 through 85 the appropriate vents open and close as they should for AC and Heat.
With the Ignition 'ON' when if I turn the mode switch to any of the 'ON' positions if I hear the relay behind the driver side cheek panel click, the blower motors will turn on. Sometimes I hear the relay click-click-click and the blower motors will not turn on or sometimes they will.
If the blower motors do turn on and I leave the system 'ON' it may work for minutes, hours, days or weeks, then suddenly it will stop working until it happens to turn on again.
I have power throughout the system fuses whether the blower motors turns on or not.
The question is whether it is the mode switch or the driver side relay.
I don't want to buy one then find out it is the other or maybe it is something totally different.
Anyone?

 

I hate to break your heart but you will need to remove each blower case assembly from under the dash, a pita on a good day.

chances are the blower motors are covered with the grime of the centuries and there's your problem, I already went through that, happy to say.

Also on the passenger side: at the darkest corner under the blower case, towards the right, there is a little Incoming Air Sensor circuit-board which is probably covered with grime too. Take a toothbrush and clean the surface, see if any miracle happens.

Otherwise if the Service Manual has any good section, it is the instructions to remove the blower cases. You'll need 7/16 or 11mm sockets for the bolts, a long extension and ratchet. You will need a piece of wood to wedge it into the recirculate flap to keep it open as you remove the case.

follow the Service Manual. I do not think it is the Mode Switch or the giant relays.

 

@ Jose: I know it is difficult I did it so no need. New blower motors installed eighteen months ago when I replaced my heater core.
Tested both motors today and the are fine. Re-read my post. The problem is intermittent.

 

First thing to do is remove the driver or left hand cover by removing the two screws for the vent foot well vent. There you will find two loose brown wires with grey insulators. Connect or short them with a jumper wire and see if your issue goes away. This is the circuit for the heater core temp sensor. It can often wear out.

If the issues resolves you will need a new 80C temp switch installed on the heater core pipe.

If the issues doesn't go away you may need a new right side control assembly.

 

you many want to see this.
https://www.jaguarforums.com/forum/a...p-img_0259.jpg

https://www.jaguarforums.com/forum/x...or-help-55798/

 

My s3 had the same problem. Sometimes it worked fine, other times it would take forever to respond. Turns out it was the amplifier. I installed the manual control switch sold by Jag-aire. Problem solved. Talk to Gary at jag-aire; he is an expert and can help you diagnose the problem. Of course, Jose's advise is always sound and dirty and loose electrical connections are always a problem in old Jaguars.

 

I like to begin with the easy stuff

If jumping the wires with the gray connectors doesn't pan out.....

Go right to the relay and check the connectors. It isn't unusual to find some that are corroded....or even obviously overheated from excessive resistance. In fact, I think you can evidence of this in the picture posted by ICS. Look at the red wire.

Cheers
DD

 

I jumped the wires with the grey connectors(See PIC 2) and I got the relay clicking on an off a few times and then the blower motors started to work in LOW, AUTO and HIGH. Without the jumper, the blower motors only work in DEFROST.
I also noticed that the green wire connected to the relay (Pic 1) looked burnt.
What do I do next? Can I leave the jumper connected in the interim until we figure out what part to replace?
Given that the green wire is burnt, should I replace the relay/s with all the white connectors shown in the pic.
I also noticed that the PO had connected the radio wire (RED) to the brown/white wire going to the relay. See the blue connector on the brown wire. I will relocate the red radio wire while I am trying to resolve this issue.

 

So I just tried to turn on the blower motors with the jumper and nothing happened. The relay is only clicking on and off. I guess the problem is elsewhere.

 

Leave the jumper wire in place for now and check your fuses, then start the process of elimination on the rest of the system.

 

@icsamerica: I left the jumper in place and all my fuses are good.
Here is what I found:
If I turn the temp switch to 85, The servos start to work. When the servo completes the cycle the blowers turn on.
If I turn the temp to 65 the blowers shut down. The servo begin to cycle and at the completion of the cycle the blowers turn back on
I change the temp back to 85 the blowers shut down and the servo cycles and upon completion of the cycle the blowers turn on.
So messing with the temp controls cause the blowers to shut down until the servo set the system to whatever position it has to be in and then the blowers will turn back on.
Any change in the temp setting will cause the blowers to shut down until the servo activates the unit to the desired temp setting.

 

Which doesn't sounds right.

When you change the temp setting the blowers should stay at the existing speed until and unless the system decides that a different fan speed is needed.

Um....I think.

I'm not near my car right now so I can't check.

Cheers
dd

 

OK, good.

That's something.



Right. That's how it should be.



Rather common


Yes, you can leave it in place as previously mentioned....permanently or temporarily.

Those wires go to a temp switch mounted on one of the heater pipes. The sole purpose of the switch is to prevent the fans from operating if two conditions simultaneously exist: 1) the system is set to provide heating 2) the coolant entering the heater core isn't enough to provide heat.

What to do next?

Begin with what you can already identify as a fault and work from there. In this case, repair any bad or suspicious connections at the relay and retest the operation



Clean and repair the connections first. Replace relay if needed.

The relay (which is actually 4 relays in one package) can be tested if you have a test light

The brown/white white is 12v constant. The radio being tapped into it, in and of itself, shouldn't be a problem....unless perhaps it (the NW wire) was damaged by the splice.

Cheers
DD

 

Hi Sanchez, Did you ever figure out what this problem was? I am having an intermittent blower issue as well and it sounds somewhat like yours.

 

I'm reviving Sanchez' thread because I am having, what I thought to be an intermittent Fan Issue. Fans are not coming on,

So far I have checked and replaced fuses. I am getting 12V at the Brown and White Wire. 3-4v on the Green and Slate with the key in the start or car running position. That is to say with the car turned off and turned on.

I have jumped the Brown and White to the Green and Slate and the fans work with the wires jumped.

I do not believe I hear clicking from the relay when the car is turned on. But I don't know when the relay would "Click". Does it click when you turn the selector knob or only when you turn the key for the first time. Of when you do anything?

When it last worked it was very low speed fan so I think the setting is stuck on "Low"?

I can hear flaps turning when I change the speed from Off to Low to High to Defrost.

Two days ago the whole thing was working and I was getting air appropriately from each setting.

I have been looking at the wiring diagram and can't make anything out of it yet?

How does one test the relay?

I have a multimeter and have run down electrical gremlins in the past. But I am not auto electrician.

 

in my experience the red relay for the auxiliary under bumper fan is somehow related to the a/c system. This relay is located by the washer bottle.

I had a symptom where nothing in the system would work properly and I noticed the aux. fan was not coming on either.

I replaced the red relay and bang! the whole system started running perfectly.

what is the relation? I have no clue. But I now have spare red relays handy.

 

There's no intended realationship that I can see.

However....

Sometimes failure of xx-circuit or xx-component can cause weird results via back-feeds. A well known example is a blown antenna fuse causing the door lights to stay on 24/7/365! I don't understand exactly how that happens....but it does

Cheers
DD

 

I'm a bit tired and bleary-eyed so I can't offer much at the moment. But, have you examined the connections at the relay pack? Over the years I've seen 2-3 Series IIIs where the connections/plugs were loose or dirty....causing high resistance and melting the connection and/or plug.

Cheers
DD

 

!!! That explains all those MELTED (and LOOSE) connections I found hidden away in Nix's innards, and the Unmistakable smell of Hot Electric during the first few months of my ownership!

Not having a KLOO what I was doing, I cleaned and tightened them and simply re-plugged them together.
No further smell of Hot plastic or Burning insulation.
(';')

 

So a bit more information.

There are only 2 clicks from the relay when the mode selector switch is turned. Those clicks occur when the mode is turned either to or from (ie "selected") the "OFF" position or when the mode is turned to or from "DEFROST". The Servos are functioning in all modes. I believe this rules out the Mode Microswitches as a potential problem.