Late Shadow 11 panel light relay - Page 2 - Rolls-Royce and Bentley Forums
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post #11 of 19 (permalink) Old 08-18-2019, 05:14 AM Thread Starter
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Thanks Jake,


Wise advice is always appreciated.


I am trying to plan my approach so I don't end up in the Frisby Flop position over the car sill/runner for too long.


I now see from the electrical schematic that I have what looks like a standard Lucas or Bosch type relay before the dimmer switch, then the dimmer switch variable resistor, and then I see another unit named 'Panel Light Control Unit' which looks like a diode+transistor+resistor combination.


So it could be a fault possible on 3 items. What I don't know is the position now in the car of the Panel Light Control Unit so am trying to see if I can find where that was put in the car.


I have googled and tried to find the part in Flying Spares catalogue so I can at least see what one looks like as again the schematic clearly shows dotted lines around both the relay and Panel Light Control Unit separately so I am assuming they are two different items.


Any further advice appreciated from all.
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post #12 of 19 (permalink) Old 08-18-2019, 06:14 AM Thread Starter
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Update......looking at the drawing of component location Robert directed me to I think item 12 are the two parts... ie the relay and the Panel Light Control Unit they refer to as dimmer unit. The 'dimming switch' (potentiometer) that is in the cabin for the driver to use then does not appear on this sheet but I know where that is anyway.


It looks to me like the dimmer switch potentiometer for the driver will be a low current item and interacts with the 'dimmer unit' which then takes the load of all the panel lights.


I still cannot find any part catalogued for sale to replace this unit if it is this part that is faulty, but if it is just some simple electronic circuit I should be able to repair it if it comes out easily.


I can do a temporary loop as Shadow 11 advises from the relay to the panel lamps so at least they can be seen at night but not able to be dimmed.


Thanks
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post #13 of 19 (permalink) Old 08-18-2019, 11:21 AM
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I would suggest the bypass option myself...the panel lights are not bright enough to require a dimmer in the first place. I upgraded all of my panel lights with LED versions of the same and it looks great, also, with LED bulbs I should never have to go in and replace them again, nor should the next custodian.

Cheers!

"Gracie"
1979 SSII
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post #14 of 19 (permalink) Old 08-18-2019, 02:47 PM Thread Starter
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Thanks jonnyc,


Obviously it is not my decision as it is someone else's car but I will put forward the proposition. My intention was to do the bypass as a temporary fix until I repaired any detailed component fault.



Looking at the circuit the 'Panel light control unit' is just a diode, resistor and transistor and once I get it out I can check and replace those components for pennies (cents). I just need to check if the transistor is a PnP or an NpN, hopefully some markings will be on the components.


The relay is not an issue as they can usually be opened and cleaned but I have a lot of Lucas and Bosch relays anyway on hand.


It would probably be more work for me to remove all the woods and instruments to change each lamp than repair the circuit electronics.


I assume that with your mod the LED panel lights then, they are not dimmable anyway? I agree though I have never even used the dim on my MGB dimmer and I just leave the panel lights on maximum and even have magnolia bright dials. My RR is not a potentiometer adjustment just a fixed 3 position variable click switch.



I changed my whole house to LED several years ago but it was sometime till I got to get the dimmable LED lights available for certain rooms and to be honest the dimmable LED ones do not perform that well. If set on low dim they struggle to 'excite' and light up again until the switch is turned to maximum and then turn the dim switch down too far they just cut out. They just don't really dim either that low or have the same range compared with the old tungsten ones.


BTW I have drafted a response to your seatbelt question and will post it up as a reply in the next day or so just for interest.


I will update the findings on the panel lights tomorrow once the blood has travelled back to my feet.


All the best


Steve
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post #15 of 19 (permalink) Old 08-21-2019, 12:09 PM
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Hi Steve,

I ended up changing to the LED versions of the panel lights because I had several bulbs blown out, figured since I was in there I may as well change them all out to LED. There's a company here that makes a direct replacement in LED so it was as easy as replacing the old bulbs with new. The name of the company escapes me now. I agree that they are probably not dimmable but since I like them bright and I bypassed the dimmer not an issue for me. Thanks in advance for the seatbelt answer...I cant believe how little slack they have compared to newer vehicles.

"Gracie"
1979 SSII
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post #16 of 19 (permalink) Old 08-22-2019, 09:16 AM Thread Starter
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Cool

Well I got the panel lights working eventually but it was not that simple.


Whether it is all wired correct at the main fusebox was hard to know as the radio aerial had seized and the owner had removed the fuse as it kept blowing if radio turned on.



As a result he had just fitted CD player into the glovebox with a flylead to add the MP3 or iPod and a couple of speakers under the dash facia and done away with using the radio albeit still fitted.


Now that is where the search finally took me sorting out the panel lights.


Whilst there is a 10 amp fuse for panel lights/control unit and dimmer circuit clearly marked in the fuseboard the actual supply to the relay is/was linked to the 10amp fused labelled as radio/aerial. So without this fuse in place the panel light relay would not energise to make the panel light control unit and dimmer send 12v to the panel lights which supply comes from the fuse marked as panel light.


So what started as a panel light issue ended up with me removing aerial cleaning shafts and regreasing the aerial motor so I could get that fuse for aerial/radio back in place. Anyone that has done this also knows it means dropping the wheel arch liner so a big job.



That then I thought would now solve the panel light illumination problem..... but alas whilst I now had supply to the panel light relay and it was allowing the Dimmer potentiometer and control unit back with a supply link the control unit was still found faulty.


That fix actually though was quite simple and exactly what Shadow11 ended up having to do.


Just remove the red and green trace wires with the two spade terminals and discard. One is from relay one from control unit.


Also remove the twin red white trace wire at the control unit and fit direct to relay in place of the red/green wire and this will then give power to panel lights at full illumination at least.


My intention was to do a circuit repair to the panel electronics light control unit but the whole bracketry it is embedded into has fuel pump and other relays attached to it so seems to also act as the heatsink for the control unit and a huge bracket for all the relays.


Given the time constraints of fixing other things I decided to order a second hand unit which is NOT gauranteed functional but was cheap. It comes with all the Lucas relays so I can now check/repair and have it ready for the next time my friend visits and we can just do a quick changeover and then I will repair his unit too and hold for a spare for someone later.


My friend left quite happy last night with music playing from the radio, and able to see the gauges/dial in the dark now.


Thanks for all the support on issues but just wondering if someone with later SS11 could just pull the radio/aerial fuse on their car and see if their panel lights do go out which would confirm my findings on different fuse supply to relay.


Steve

Last edited by Steve E; 08-22-2019 at 09:23 AM.
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post #17 of 19 (permalink) Old 08-22-2019, 10:37 AM
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Steve.

Yes, the instrument lights will not work if the radio/aerial fuse has blown.
Also, to be sure, I did pull the fuse on my Shadow and no panel lights.

When I first had my Shadow there were many electrical faults ie. coolant warning, interior lights, various issues with ACU wiring, radio and someone, in there wisdom, had fitted a car alarm.

I did initially get a auto electrician to look at these and a few more problems and he said unless I had a very full wallet he would not want to get involved with it.

After spending many hours reading and studying, I fixed all the problems myself. Guessing, but I would think to get them all sorted, it took a month of work.
Luckily I have had no problems since apart from the one bulb blowing.

Jake.
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post #18 of 19 (permalink) Old 08-22-2019, 11:11 AM Thread Starter
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Thanks Jake for the clarification, at least the electrics are fairly as factory then.


Not that it makes a lot of sense to me WHY that there would need to be 2 separately fused 12v supplies for the panel lights to function and one not even referred to or easily found. I suspect a lot of RR/B owners may have had the radio/aerial fuse blown and no panel lights then when checked the 'panel light' fuse as indicated it was good. The only thing I could assume it was to protect the electronics in the panel light control module from any damage in some way.



Now the task is to find somewhere in all the 700 pages in the manual or on a supplement schematic to see just if it is made clear.


I am having a rest today


Regards


Steve
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post #19 of 19 (permalink) Old 08-22-2019, 01:41 PM
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Steve.

There are two fused supplies to the instrument lights so that when the ignition is switched off the radio/aerial fuse is isolated then the instrument lights switch off, leaving the exterior parking/side lights on. Save the battery?

Jake.
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