Heater Blowers on 1991 XJ40

Hi reading about other chaps problems with heater blowers, I have similar problem with my right hand drive XJ40 in UK

Took drivers side motor out & put new Darlington unit in to solve same problem as others re fast blowers ok, but no low or medium speeds.

Sadly, not much difference! So still have fast & defrost speed blowers, but no lower speeds. Apart from, if I put it on MEDIUM speed, it blows for a couple of seconds, and stops. Any ideas folks?

Rgds

Neil

I’m no expert on this, do you have the wiring schematic for the system? there’s a heat sink for the blower motors and ambient sensor, if the medium speed works for a few secs/ then it’s losing power most likely - hopefully not due to an overheat problem, i can send you an schematic extract in colour if you want…tom

Ah thanks Tom that would be useful please.

Rgds

Neil

Neil,
schematic below should cover the info…Tom

Hi Tom and thank you for the diagram.
I cant see connections in diagram to blower rotary sw, or SLOW blower speed controlling item.
Would you advise please?
Rgds

Neil

Neil, I am out of my element here as my car is a '94MY but my understanding is the climate control system for the '91MY is similar to the '89MY. Here is a link to the electrical guide for the '89MY; Fig 28 is the c.c. system. Hope this helps.

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neil,
i can post the next system for the control unit, still a sealed unit but you could test using a multi meter, do you have the heating/cooling switch control assembly off? there’s 2 relays mounted behind that panel as well. the makers didn’t want to make it easy for us to fix like the old models.

N/U for brown with blue tracer, I get U for Ultramarine but N stands for ???

larry,
in all jaguar schematics N = brown … U = blue nothing fancy just blue, if any of the colours are a lighter colour it would be for eg: LU/ = light blue, very early jags used a dark green so it was a DG

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Hi Tom. Havnt got it out yet, but do please post more inc method to remove the sw panel please.
Rgds

Neil

neil,
i’ve loaded the picture in this chat, to remove the switch panel there’s 6 screws i believe which also contains the radio, if you can’t see the picture i posted then message me

Hi Tom.
Thank you, but cant see pic at moment.

Rgds

Neil

Larry, this is from Jaguar’s “S6593_Electrical Guide XJ6 Sedan Range 1993”:

My supposition is the color codes were determined through a process of prioritization and elimination, to wit: black is probably the most used color as it is generally used for ground / earth / negative, which every circuit has, so ‘B’ was chosen for black. Red is commonly used for the other (positive) side of a simple two wire circuit - think of battery cables - so ‘R’ was chosen for red. Now there are other colors that begin with ‘b’ - brown and blue. For brown, ‘B’ is assigned to black, and ‘R’ to red, so what about ‘O’? Well, we must think ahead - we have orange to deal with, so let’s use ‘O’ for orange. So what about ‘W’? Again, thinking ahead, there is white - let’s use ‘W’ for white. So through elimination, what does that leave for brown? ‘N’. OK then, how about blue? ‘B’ is taken, how about ‘L’? We want to use ‘L’ to indicate light, as in light blue or light green. How about ‘U’ then? Fine, we will use ‘U’ for blue. Considering the other colors yet to be dealt with, there are purple and pink. The letter ‘p’ appears twice in purple, and only once in pink. So let’s use ‘P’ for purple IF we can use a different letter for pink. Could we use ‘I’ for pink? Well, anyone that has served on a standard-setting committee knows the use of ‘I’ is to be avoided - it should be ‘we’ did this or that, not ‘I’. :grin: Anyway, moving on, ‘N’ was assigned to brown, so that leaves ‘K’ for pink. Fine. And thus purple gets ‘P’. I won’t further bore you with the rest of the process, I imagine you can fill in the rest of the story. By the bye, was I on the committee that came up with these color codes? Heck no! Am I an electrical engineer? Double heck no! But I did stay at a Holiday Inn Express one time, and dreamt about these color codes…in case you are not familiar with the Holiday Inn Express reference: https://youtu.be/eHCTaUFXpP8

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Neil,
send me a private message with your email

Hmmmm,
bit of mono logging there Mike, have you been smoking a bit of rat-funk :laughing:

Hi Tom. How do I send privately to you?
Rgds

Neil

Neil,
left click on my avatar 7 it will show my details with a box " message"

not 7 = & or email me> jagschemes@live.com.au

Nope, not me…sorry if I overstepped.

Neil…

First thing to do is correctly replace the correct Darlington (and if you’re confident you’ve done this) then test it in the “Manual” vs “Auto” mode in the climate control panel. In the manual mode you bypass all of the auto sensors. But I’m not really sure that makes any difference to this problem.

The symptoms you describe almost ALWAYS indicate a failed Darlington transistor. In fact in the 20+ years that I’ve been on this forum I can’t remember those symptoms ever being anything else.