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Aug 16, 2022 20:38:17 GMT
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This is for a friend's 1976 Shadow 1 that he has owned for years. It has been off the road for the last couple of years, and over the last few weeks, in between helping out with other things, I have been working my way through the electrical snag list, which is the reason he took it off the road. It now has fully working windows, central locking and courtesy lights - when I started, only the driver's window worked and both rear doors wouldn't even open at all... However I have been having no luck so far at resurrecting the head lights which are the last things that needs doing so that it can be used again. Symptoms are as follows: - No main beam at all. Headlight flash relay makes a normal sounding noise, but there is no result at the head lights. - Left hand outer headlight has dip only, & cuts out with dip switch. - Right hand outer headlight is also on dip beam (confirmed by which wire is powering it), but doesn't go out when dip switch is operated... - Lh is drawing volts through both fuses 4 (headlights) and 9 (lh dip) - removal of either fuse results in that light not working. - Rh unaffected by removal of fuses 4 and 10 (rh dip). fuseboard layout:  (HL cutout referred to on the fuseboard is an auto-resetting thermal cut out)
- Main beam warning light not working. - Full continuity between relevant wires on outer & inner headlights (outer are main & dip, inner are only main) as each side has one main feed for main beam and also for the earth. - There is also full continuity of headlight looms from bulkhead / scuttle connector plugs through the engine bay to the lights. - Side, marker, & tail all working, so the main light switch is operating correctly. As the looms to the lights are intact, and the switch is working, our current train of thought is that the problem is the relevant relay(s) - does that sound right? Whilst I can find several relays scattered around the engine bay and also up behind the dash, I have been unable to identify any, except the headlight flash relay. The wiring diagrams & manuals are not especially helpful with this either, and searching online hasn't brought up the answer either (Shadow 2 and later are different). Engine bay relays (one with blue tape is the flasher - behind it may potentially be other relays but the ducting will need to come off to get in there):  and close up:  Under the glovebox (black box with red button is the electric windows thermal cut-out):  There are also some under the dash on the driver's side - visible through this aperture which is normally covered by a padded leather trim piece:  Looking to the left  and right  As those last relays are very difficult to access, I don't want to pull the dash out unless I know that they actually are the headlight ones! Any advice in solving this would be extremely appreciated! |
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Last Edit: Aug 16, 2022 20:40:06 GMT by Paul H
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jimi
Club Retro Rides Member
Posts: 1,815 
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Aug 16, 2022 22:55:25 GMT
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Without seeing a circuit diagram, its next to impossible to offer any advise, do you have the circuit diagrams ?
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Black is not a colour ! .... Its the absence of colour
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Aug 16, 2022 23:11:50 GMT
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Yes! rrtechnical.info/sy/tsd2476/16.pdfThe theoretical wiring diagram starts on p 73, and the practical wiring diagram on p 104. Unfortunately, the tracers on a lot of the actual wires are no longer clear, which doesn't help. The theoretical wiring diagram can also be rather misleading, and is best viewed in the context of the practical diagram.
I've probably been staring at it for too long, from when I was using it to sort out what was wrong with the electric windows and central locking...
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jimi
Club Retro Rides Member
Posts: 1,815
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Aug 17, 2022 16:35:11 GMT
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Haven't been able to spend any time looking at the diagrams yet, a quick glance shows them to be .... "interesting" 😳
One thought occurs to me, you have removed each lamp (from the headlights) and checked they work as they should ?
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Last Edit: Aug 17, 2022 16:49:43 GMT by jimi
Black is not a colour ! .... Its the absence of colour
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Aug 17, 2022 19:15:18 GMT
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You could try a fused supply direct from the battery and probe the light terminals , this will test the light units and more importantly the EARTH connections.
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Aug 17, 2022 20:45:05 GMT
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Thanks chaps!  Haven't been able to spend any time looking at the diagrams yet, a quick glance shows them to be .... "interesting" 😳 One thought occurs to me, you have removed each lamp (from the headlights) and checked they work as they should ? That is certainly a fair description of the wiring itself too. For example, there's something like nearly twenty wires running just into the driver's door. Because it's a Rolls-Royce, there is no visible wiring run into the door either - the loom is threaded inside a hollow check strap, and the other week, I had the fun of replacing a couple of those wires when I was fixing all the electric windows. The level of kit for a 1976 car is certainly impressive, but it's also all done with 1960s tech, and very over engineered... E.g. the central locking solenoids are like bolt guns, the thunk when all four activate is loud, and would make a good movie sound effect for a bank vault. You could try a fused supply direct from the battery and probe the light terminals , this will test the light units and more importantly the EARTH connections. The lights themselves are good & have been tested (inner pair are brand new as old ones were found to be duff the other week when I first started looking at the snag list), and earths have been checked carefully as well. Both outer lights do illuminate on dip, and main beam on those uses the same earth. Volts and earth for the inner lights are strung immediately from the outer lights (& there is proper low resistance continuity), so once main beam is behaving on the outer lights, the inner ones *should* also come alive. The issue seems to be the power supply inside the car / behind the dashboard, and we have yet to find the relevant relay(s). However I managed to find a parts diagram on an R-R specialist's webshop which seems to locate where they are hidden & now the vague written descriptions info in the factory manual finally make more sense and I am intending to investigate again tomorrow. Fingers crossed...
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Last Edit: Aug 17, 2022 20:45:43 GMT by Paul H
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jimi
Club Retro Rides Member
Posts: 1,815
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Aug 17, 2022 22:39:48 GMT
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Since you have proved the light units and the wiring to them then the fact that the headlight flash relay activates but the lights (and main beam indicator) do not illuminate would point to a lack of power getting to the lights. Which means the problem is further back, I'd say your on the right lines trying to locate the components behind the dash.
Have you checked if the head safety relay and the head safety cutout are in fact passing voltage through to the lights ?
Finding (and being able to access) the components will make a big difference to identifying/repairing the problem, in basic fault finding terms, track the voltage from the battery onwards through the circuit and you'll find the problem (which is, I'd guess what you are doing) keep at it you'll get there 👍
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Black is not a colour ! .... Its the absence of colour
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Aug 18, 2022 20:28:38 GMT
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Thanks chaps! Haven't been able to spend any time looking at the diagrams yet, a quick glance shows them to be .... "interesting" 😳 One thought occurs to me, you have removed each lamp (from the headlights) and checked they work as they should ? That is certainly a fair description of the wiring itself too. For example, there's something like nearly twenty wires running just into the driver's door. Because it's a Rolls-Royce, there is no visible wiring run into the door either - the loom is threaded inside a hollow check strap, and the other week, I had the fun of replacing a couple of those wires when I was fixing all the electric windows. The level of kit for a 1976 car is certainly impressive, but it's also all done with 1960s tech, and very over engineered... E.g. the central locking solenoids are like bolt guns, the thunk when all four activate is loud, and would make a good movie sound effect for a bank vault. You could try a fused supply direct from the battery and probe the light terminals , this will test the light units and more importantly the EARTH connections. The lights themselves are good & have been tested (inner pair are brand new as old ones were found to be duff the other week when I first started looking at the snag list), and earths have been checked carefully as well. Both outer lights do illuminate on dip, and main beam on those uses the same earth. Volts and earth for the inner lights are strung immediately from the outer lights (& there is proper low resistance continuity), so once main beam is behaving on the outer lights, the inner ones *should* also come alive. The issue seems to be the power supply inside the car / behind the dashboard, and we have yet to find the relevant relay(s). However I managed to find a parts diagram on an R-R specialist's webshop which seems to locate where they are hidden & now the vague written descriptions info in the factory manual finally make more sense and I am intending to investigate again tomorrow. Fingers crossed...Having some relevant information will definitely help . Good luck
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Aug 24, 2022 20:38:12 GMT
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Well, it is almost all sorted now! Lack of main beam turned out to be a dodgy connection downstream of the dip switch. However this wasn't identifiable until I was able to do further voltage and continuity checks once the relevant relay board was extracted from the engine bay, under the trunking in the first photo that I posted. The manual says to remove the washer bottle, two nuts and two bolts then it slides out. Except that the bracket for the throttle linkage was blocking it. This bracket also has one of the pulleys for the handbrake on it. Access to all the bolts wasn't easy as the bay is very full, but it came out eventually, allowing access to the relay board. The offending bracket was presumably a Shadow 2 part which had been introduced early (as it is a very late Shadow 1, there are quite a few such features elsewhere...), as that had a relocated relay board. To allow future access to the relay board, the relevant section of the bracket was cut off before it was refitted. It only held a relay which can be mounted in the same general area anyway and that will be easily detached for access. The PCB for the relay board had some damage from overheating (presumably due to various poor connections), so required degreasing and cleaning up as the carbonised area of the back board seemed to be allowing current to be conducted. Once that was dealt with, it was then sending the volts where they should go without any issues. The seemingly functioning flasher relay turned out to be dead. It activates the coil, but doesn't actually switch the cross over to flash the lights. I liberated one of the air con relays*, which has matching terminals and change-over circuit and the headlight flashers now work. The main beam tell tail is also now working - simply a dodgy earth as the tab on the bulb holder wasn't engaging properly with the speedometer body. Not fun to sort though as the wire on it is very short so I had to reach up under the dash and do it all by feel with just a small aperture to view through... *The air con was ditched years ago, so those relays aren't doing anything, and they are located on the same board as the headlight safety relay. Talking of that, the headlight wiring is very odd... There isn't actually a main beam relay - it all runs straight through the dip switch. Whilst I originally thought that the headlight safety relay was the problem, it was actually doing its job properly, as it turns out that it is designed to maintain power to the offside dip if there is no power to main beam. I can only assume that this was considered to be a modern safety feature when the electrical system was designed back in the early '60s... Still some reassembly to be done, the central locking solenoid that I previously fixed has stuck again so requires further attention and then the leaking heater tap needs fixing too...
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Last Edit: Aug 24, 2022 20:39:46 GMT by Paul H
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jimi
Club Retro Rides Member
Posts: 1,815
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Aug 24, 2022 21:44:20 GMT
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Well done, knew you would get there  |
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Last Edit: Aug 24, 2022 21:44:57 GMT by jimi
Black is not a colour ! .... Its the absence of colour
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Aug 25, 2022 12:15:52 GMT
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It's definitely been a very steep learning curve! Prior to working on this car, I'd only used a multimeter a few times. Now it feels like second nature to hook up a lead to extend a circuit to check continuity, or to plug in short connector wires to power only one wire at a plug connector etc.
I know that my friend is certainly looking forward to being able to use it again. Quite a while back, he had reconditioned the engine (& incorporated a few mods internally to solve some design issues with the coolant galleries) before putting it on the dyno in his test cell as R-R never quoted power figures. IIRC, it produces about 230bhp, but with 150bhp at pretty low rpm and a torque curve like table mountain. The reason for the rebuild was simply old age - various gaskets failing, but even at 100K, all the bearings etc were still well within factory tolerances.
He has also previously fully rebuilt the brakes and hydraulics (including the rat trap). Front caliper rebuild kits are the same as a similar era Ford (think it's Late Cortina / Sierra) but it needs double as there are two calipers per disc to run the dual circuit system. I think that this is the first time that the electrics have needed such heavy attention though so not bad for 46 years old especially given the complexity of the car. I've been doing it as he is currently very busy rebuilding a De Havilland Gypsy engine from a Tiger Moth and I've been helping out with smaller and less skilled stuff on that too, cleaning up & bead blasting parts as well as doing all the split pins on the crank.
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