Heated Rear Screen Timer

Interior and Exterior bodywork Faults and Fixes
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Mike Rometer
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Heated Rear Screen Timer

Post by Mike Rometer » Thu Sep 12, 2019 10:00 am

Did a search and drew a complete blank. This morning, when I was due to go out, there was dew (note the spellings ;) ) on the screens. On start-up the auto wipe cleared the front, but the HRS didn't come on so I switched it on manually. Before I got to the end of our road (30 secs. max.) it had turned itself off again and the screen wasn't even touched. I turned it on and it stayed on a little longer this time but not enough. Ditto-repeato all the way there. How long should it stay on and what other criteria, if any, affect it. This morning it was less use than a chocolate teapot! I got to my destination with the screen in the same state as I left home. We're not talking heavy dew here, not enough to even run in the draught over the car.
Jag No 3. 2 Litre petrol Prestige 200. Italian Racing Red. 65 plate

My other vehicle is coal fired. 8-) (very lo-tech)


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Vespa
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Location: North West UK

Re: Heated Rear Screen Timer

Post by Vespa » Thu Sep 12, 2019 10:11 am

I am sure that this is timed according to the outside temp. When it does get cold and on auto I think it varies from 6-10 mins before switching off.
180 diesel XE R Sport, with many extras :D and working stop/start :lol: Made to work Feb 2019 by me


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Vespa
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Re: Heated Rear Screen Timer

Post by Vespa » Thu Sep 12, 2019 10:25 am

Here is an explanation from my gathered info........
Heated rear window operation is only enabled when the engine is running. The ATCM controls operation of the heated rear
window using a relay in the RJB (Rear junction Box). When a request is made for heated rear window operation, the ATCM
broadcasts a message to the BCM/GWM on the MS CAN comfort systems bus, the BCM/GWM. On receipt of this message, the
RJB energizes the relay by providing a ground path for the relay coil. This allows a battery feed to flow across the relay to
power the heater element.
There are 2 modes of heated rear window operation; manual and automatic.
Manual operation is activated by pressing the heated rear window switch. When the switch is pressed, the status Light
Emitting Diode (LED) in the switch illuminates and the rear window heater element is energized. Manual operation is
discontinued when the heated rear window switch is pressed a second time, between 5 and 21 minutes have elapsed
(dependent on ambient air temperature), or the engine stops. If manual operation is discontinued by the engine stopping, the
previous heating phase is resumed if the engine is re-started within 30 seconds.
There are 2 variants of automatic operation; automatic operation at the start of a journey and automatic operation during a
journey.
Automatic operation at the start of a journey is initiated for between 5 and 21 minutes (dependent on ambient air
temperature). The higher the ambient air temperature, the shorter the time. In this instance, the switch LED is illuminated
and the heater element is energized. In addition to shorter operating times in temperate winter conditions, there are condition
qualifiers to prevent subsequent operations once the cabin or engine is warm, or there is a significant sunload. Automatic
operation is discontinued if the heated rear window switch is pressed or the engine stops
180 diesel XE R Sport, with many extras :D and working stop/start :lol: Made to work Feb 2019 by me


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Vespa
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Re: Heated Rear Screen Timer

Post by Vespa » Thu Sep 12, 2019 10:26 am

Also nothing to do with this I have the SVP question submitted to JLR
180 diesel XE R Sport, with many extras :D and working stop/start :lol: Made to work Feb 2019 by me


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Mike Rometer
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Re: Heated Rear Screen Timer

Post by Mike Rometer » Thu Sep 12, 2019 10:28 am

I don't think I have it set to auto, seem to remember switching that off. Outside temp was about 15C. Normally the car would have been in the carport and wouldn't need the screens clearing.

Edit:- Cheers for the above Vespa.
Jag No 3. 2 Litre petrol Prestige 200. Italian Racing Red. 65 plate

My other vehicle is coal fired. 8-) (very lo-tech)


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Mike Rometer
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Location: N. Staffs

Re: Heated Rear Screen Timer

Post by Mike Rometer » Thu Sep 12, 2019 11:16 am

I have checked the settings for my HRS and Auto is turned off. There is another setting on that screen, 'Auto Power', which is set to 'Low'. What exactly does that control?
Jag No 3. 2 Litre petrol Prestige 200. Italian Racing Red. 65 plate

My other vehicle is coal fired. 8-) (very lo-tech)


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Vespa
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Location: North West UK

Re: Heated Rear Screen Timer

Post by Vespa » Thu Sep 12, 2019 11:45 am

Fans speed.
180 diesel XE R Sport, with many extras :D and working stop/start :lol: Made to work Feb 2019 by me


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Mike Rometer
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Re: Heated Rear Screen Timer

Post by Mike Rometer » Thu Sep 12, 2019 6:54 pm

Vespa wrote:
Thu Sep 12, 2019 11:45 am
Fans speed.
Ah!
Jag No 3. 2 Litre petrol Prestige 200. Italian Racing Red. 65 plate

My other vehicle is coal fired. 8-) (very lo-tech)


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Mike Rometer
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Joined: Tue Mar 19, 2019 10:28 am
Location: N. Staffs

Re: Heated Rear Screen Timer

Post by Mike Rometer » Thu Oct 03, 2019 9:31 am

Still of the opinion that the HRS is as much use as a chocolate teapot (or an ashtray on a motorcycle). This morning, dew on the outside and steamed up lightly on the inside. Outside temp a balmy 5c. brrrr! Heated front and rear screen (and heated seat and wheel :D ) turned on. The front stayed on, the rear turned off before the insides had cleared even halfway, and nothing shifted from the outside. It was one of the rare times I would have used the "Defrost" on the X-type, which would have shifted it in less than two minutes. Should I have hit the "Max"? It doesn't seem to be quite the same thing.

The HRS could of course have a faulty relay, or somesuch.
Jag No 3. 2 Litre petrol Prestige 200. Italian Racing Red. 65 plate

My other vehicle is coal fired. 8-) (very lo-tech)


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Vespa
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Location: North West UK

Re: Heated Rear Screen Timer

Post by Vespa » Thu Oct 03, 2019 9:57 am

Just manually press it back on and it will stay on longer to a preset timing.
180 diesel XE R Sport, with many extras :D and working stop/start :lol: Made to work Feb 2019 by me


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