| Author | Message | ||
     Christopher Williams Unregistered guest |
Hello all, I have a 1989 Mulsanne S, and my rear defrost is not functioning. I have tested the fuses, which were good, and tested the relay, which was faulty. I installed a new relay, which worked once, then I lost the grounding signal from the ACU. Before I dig into the module itself, I wanted to ask if there is anything else that would cause the ACU to not send its ground signal. My testing was done with the switch in the defrost position. Thank you for any insight, Christoper Williams (Message approved by david_gore) | ||
| michael vass Frequent User Username: mikebentleyturbo2 Post Number: 72 Registered: 7-2015 |
Hi Chris The ecu will only set the screen on when it wants , temp difference, humitity etc So it may not be faulty ok see this http://www.rollsroyceforums.com/forums/27-sz-motorcars-1980-2003/138-heated-rear-screen-switching-question-89-turbo-r.html Mike | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1819 Registered: 6-2009 |
In digging through the documentation I have it appears that the best bet for details on the operation of the rear window demister system would be in Chapter C3 of TSD4700, but that particular section is missing in the materials scanned on the Technical Library. If anyone has hard copy it would be worth checking in that section just to see if they give the details about when the rear window demister would be activated by the ECU. Brian | ||
| Roderick Waite Prolific User Username: rodwaite Post Number: 152 Registered: 1-2012 |
Hello Christopher - agree with Mike on this - the rear window demister does not necessarily work when you think it should, and doesn't work very well when it does work. In my view it's a mistake not to have a manual control for it, and something of a nuisance. I wonder if anyone has ever installed a manual switch? Rod '84 Spirit | ||
| Dick Campbell Experienced User Username: dick_campbell Post Number: 13 Registered: 5-2015 |
Before getting into the control system I would check that there is a circuit thorough the heating element. There are two connectors buried in the rear screen sealing rubber that gradually corrode away. They go to the relay in the boot so are easy to identify. They had on my Mulsanne and the Shadow before it. If they have it is rear screen replacement. I agree with a manual switch......should not be a problem. Dick | ||
| michael vass Frequent User Username: mikebentleyturbo2 Post Number: 73 Registered: 7-2015 |
Hi Christopher I agree with Dick mine are correded ,but just a warning don't go digging around in the rubber they are very delicate connections ,do as Dick says and check first if you have continuity to ground from the relay ok , the nearest you should need to get to the screen itself are the "bullet" connectors behind the roof trim ok Cheers Mike | ||
| michael vass Frequent User Username: mikebentleyturbo2 Post Number: 74 Registered: 7-2015 |
ps what chassis number is yours Chris? | ||
| Christopher Williams Unregistered guest |
Hello Michael and everyone who responded, My chassis is #24822. I've checked at the terminal 87 spot on the relay, and I do not have continuity to ground, so I will investigate that first and find if this rear screen is still a complete circuit or if I have a broken/corroded/disconnected wire in the mix. I have poured through the repair information, and have yet to find the actual criteria that is needed for the "on" signal to come from the ACU. (Message approved by david_gore) | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 101 Registered: 7-2012 |
VIN 24822 IS A SHADOW 1 WITH MANUAL REAR WINDOW CONTROL. IT SEEMS THAT THIS BEING MIXED UP WITH SHADOW 11 AUTO SYSTEM WHERE THERE IS NO MANUAL CONTROL SWITCH, THIS BEING DONE BY THE ECU. AS I UNDERSTAND SHADOW 1 SYSTEM, THE MANUAL SWITCH IS FED FROM ITS OWN FUSE TO THE HEATED REAR SCREEN MANUAL SWITCH THEN TO A RELAY WHO'S JOB IS TO CUT OFF FEED TO HEATED REAR SCREEN WHEN THE MAIN UPPER SYSTEM SWITCH IS IN ON POSITION. THIS HAS EFFECT OF SWITCHING OFF HEATED REAR SCREEN WHEN UPPER/FRIDGED AIR IS TURNED ON, EVEN IF HEATED REAR WINDOW MANUAL SWITCH IS LEFT IN ON POSITION. | ||
| Mark Herbstreit Prolific User Username: mark_herbstreit Post Number: 141 Registered: 5-2005 |
Gordon. Chris has posted the numerical sequence of his 17 digit Vin which would look something like this in its entirety. SCBZS00??kch24822. Not to be confused with Shadow SRH24822. (assuming both right hand drive) | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 102 Registered: 7-2012 |
disregard last post please, thought I was on Shadow file!! |
