So I was working on my '90 XJS this weekend when I noticed an Ambient Air Temperature Sensor located on the panel in front of the radiators.

I thought that it must be part or the air conditioning system but when I looked at the wiring diagrams I found out that it is actually part of the windshield wiper system.

I cant imagine why the wiper system would need an ambient temp sensor. Did Jaguar decide to prevent operation of the wipers if the outside temperature is too cold or too hot?

I'm hoping someone here can explain the need for this sensor.

Thanks!

Mark

 

At about this time, heated screenwasher jets were on some cars, and also heated outside rearview mirrors. So one explanation could, repeat could, be, that the loom included all the necessary wiring etc, whether this option was fitted or not.

I fitted a NoS wiper motor, and that has a wire for heating the screenwasher jets.

Greg

 

Jaguar then changed from putting the sensor at the front of the car to putting it with the washer jets.

Paul

 

Here is a copy of the schematic;

 

Safari,

I've often wondered if the diagram for the 1990/91 cars was actually wrong. Because looking at that diagram, you would conclude that the sensor was there to protect the wipers from operating when it was too cold / hot?

However, if you look at the diagrams of cars from earlier cars (1988- 1989) and then later cars (1992 onwards) it's clear that the ambient air sensor provides a signal only to the washer jets and headalmp washer jets.

Strange....

Paul

 

I was wondering the very same thing, Paul

cheers
DD

 

One day when I have time I will trace the wire and see if it actually goes to the wiper motor as indicated by the schematic.

I have never heard of a car that limits the wiper motor function based on air temperature but I have learned that with Jaguar anything is possible!

Mark

 

It doesn't. The ambient switches on the heaters in the nozzles of the washer jets, the wiring to do this (if my motor is any guide) is partly incorporated in the feed to the motor, but does not affect motor function.

 

If you read the diagram above the wire goes to ground not the motor. The heated jets and motor probably share a ground wire.

 

Maybe I'm reading it wrong but what I see is 12V+ coming from the fuse panel into the sensor. When the sensor closes it sends that voltage to the motor.

My car has no heated jets. The only heat they see come from the V12!

Mark

PS...Post #300!

 

Bc xj,

Tks, I see what you mean. It is a poor way to draw the direction to the earth terminal, which they drew in a more logical fashion in other years. Also, in this years diagram, they didn't actually label the washer heaters which they did in both the previous and subsequent years.

Clearly the 1990 wiring diagram technician got sacked after 1 year!

Paul

 

Here is the drawing for the 1989 cars;





This does a better job of showing that the power from the temp sensor feeds voltage to the water jet heater. Where the heck is the heater located?

Mark

 

...and the 1992 diagram is even clearer on the route to earth of the jet heaters.

Paul

 

The actual nozzles on heated jest have little heater coils in them.

Greg

 

Safari, in regards to this drawing, a few times I've had the need to add a diagram to a post, but I can only do Jpeg pictures. What kind of a document this one comes from and how do you paste it here?
Thank you,

 

The electrical diagrams I have are all in PDF format. I have a Pro version of Adobe Acrobat that allows me to convert a PDF page into a JPG image. I can then take that JPG and edit it with PhotoShop.

After that its ready to upload to a message by clicking on the "Insert Image" icon at the top of the message window. Just browse to the file where the image is stored and click on the file. It will upload the image into the message.

Hope this helps.

Mark