One gets better and one gets worse
Last issue, I was trying to get the rear lights on the Robin to work, and had ordered a new pair as they were only £25 each. The new units arrived promptly and were the right ones, but looking at the condition of the ones I'd removed, I did rather suspect that they had already been replaced in recent memory.
The new ones came without any bulb holders, and both new and old units had the fog light slot blanked off and no bulb holder there. Looking at the wiring plug for the lights, it seemed that every connection pin was wired, and there was a rear fog light switch on the dash that lit up when it was switched on – even though there were apparently no rear fog lights fitted. This was a potential problem because the Robin would need a fog light for its MOT, but reading up on the regulations it seems that for a car first registered before September 2009, the reversing lights are not part of the test. And my car had bulb holders fitted for reversing lights...
The bulb holders are of a type I have not encountered before, with contact pins that sit against the metal circuit board and plastic lugs that go into slots in the light housing and lock the holder in place when it is rotated a few degrees. I tried without success to find the correct bulb holders, so if anybody can point me in the right direction for some, I would be very grateful. The bulb holders were in fact of two slightly different types – the indicator, fog and reversing light ones had only two plastic tabs and two contacts, each diametrically opposed to the other, because they only had a single filament bulb. The stop/ tail light had four contacts in a cross pattern and three retaining lugs offset to one side of the holder so that it could only be fitted one way around and you could not mix up the stop and tail light contacts.
For now I have moved the reversing light bulb holders to the fog light slots to keep the car legal. It worked, but only after a fashion. I would test the units out of the car and find they worked OK, but by the time I had fitted them back on, they would either not work at all or the indicator would flash slowly and cause the tail light to pulse in brightness in sympathy. As for the fog lights, they wouldn't play along at all!
Access is difficult to the four M5/8mm nuts holding each light unit in place, but I took them back off and used a multimeter to check for continuity between the earth pin on the light unit and each lighting circuit pin in turn, and that was good for all of them fitted with bulbs. (Incidentally, I have a new Clarke multimeter with a buzzer for connectivity, a feature that is a real bonus for jobs like this.)
Most of you will be ahead of me at this point because I have said before that the majority of electrical problems are caused by bad earths. This is especially true if activating one bulb also affects another one near it.so I turned to the downstream wiring. The loom tucked inside the OSR wing behind the light unit on that side was a bit of a nest, with a number of non-original wires spliced in. I traced these around the car to see what they were intended for. One ran all the way to the front of the car, then into the
cabin and to an aftermarket illuminated switch tucked under the dash. I had always wondered what this did (it never illuminated), but chasing the other wire from it showed that it led nowhere and was not connected, so I removed the lot.
I also found some nonoriginal black wires in the rear wing that I traced forwards to a coarse self-tapping screw that had been fitted halfway along the chassis side rail as an earth point. All well and good, but a slightly pointless exercise because the other end by the light unit was not connected to anything. Hmm... I traced the original earth wires forwards and they seemed to be firmly attached in the engine bay. I also removed and cleaned up the battery's main earth point, but that seemed fine too.
I cannot find a wiring diagram for this model, the only one I have being for the simpler original Robin from the 1970s and 1980s. So I made a note of the wiring colours used for each of the circuits on the light units just for future reference, then cut into the earth wires that ran from the light units to a multi-plug in the OSR wing. I fitted these ends with Lucar bullets, and added an additional earth wire to this. Instead of running it forwards to the DIY fitting point I'd found, it was much neater to keep the run short. So I refitted the screw just to seal up the hole in the chassis and connected the wire with a ring terminal under one of the rear anti-roll bar securing bolts. Bingo – all the lights were bright, all worked perfectly and I was back on the road.
Meanwhile, I also decided to invest in one more try at sorting out the VW Beetle and its constantly recurring CHECK ENGINE warning light, so booked it in at Hall's Garage. You may recall that the error codes keep indicating a lean mixture and a misfire, neither of which shows up in use or when the car is connected to a code reader to examine live data. Hall's first changed the fuel filter because that was really clogged up and hadn't been renewed in a long time.
This was always going to be a bit of a long shot, but it needed doing anyway. It made no difference of course, and bang on cue, the CHECK ENGINE warning light came back on after another 60 miles.
Hall's then carried out a smoke test because these engines can suffer from vacuum leaks – basically you put smoke into the air intake, run the engine and see where it comes out! There were no obvious leaks, but they noticed that the oil cap was not sealing properly, and that can let vacuum out. So they put a new one on – and then the car wouldn't run. This was actually progress of a sort, because at least now there was a 'reliable' problem to investigate!
The suspicion was that now the oil filler cap was doing its job and sealing the engine, vacuum had to be getting out somewhere else. Attention then turned to a valve in the air intake pipe – the PCV (Positive Crankcase Ventilation) valve. That would give all the same error codes as we had encountered – efficiency on cats, fuel efficiency, misfiring, mixtures... Unfortunately, it is all part of a fairly complex plastic housing. I did try to find a brand-new replacement and was even willing to pay the asking price of £175, but could find no stock anywhere. In the end I opted for the cleanest looking of the secondhand ones I could find online, which came in at £55. Unfortunately it made no difference. I suspect there is only one more report in the Beetle before I give up in frustration and bin it.