Rear offside fog lamp not working - MOT fail

[taiwan740]

My car has failed its MOT twice at two separate garages for a rear fog lamp issue.

It is irritating as many cars only have 1 fog light, and I'm pretty sure the offside fog light was never actually set up to work from the factory, it's just there for symmetry. I could be wrong though.

Anyone have any idea how I can get both rear fog lights working to make my supposedly dangerous and unroadworthy vehicle safe again? Is it as simple as install a bulb holder and a fresh bulb, or is there extra wiring involved?

[john.wigley]

Which year / model are we considering, 'taiwan 740'?

Many cars do indeed seem to have only one rear fog lamp, mirrored on the opposite side by a revering light. However, the fog lamp must be on the offside as seen from the rear. As that is the one which is not working, I strongly suspect that is why your car has been failed by the MOT examiner.

We have owned a total of 4 7-series cars, both estates and saloons of varying years, and all have been equipped with two functioning rear fog lights.

I think it likely that yours may be down to little more than a replacement bulb and/or holder. Sometimes just removing the holder and lightly polishing and/or bending the terminals in slightly will be sufficient to bring a recalcitrant lamp back to life.

Another possibility is that somebody has in the past incorrectly wired a towbar to the light unit and that is causing the malfunction. Yet another is the possibility of water ingress if the lamp unit is damaged resulting in corrosion. We had that once on a saloon when the seal failed and allowed water to accumulate inside the light unit.

Regards, John.

[GingerMagic]

Have you swapped the bulbs over, as in NS to OS just to eliminate the bulb as the culprit?

[taiwan740]

Originally Posted by GingerMagic

Have you swapped the bulbs over, as in NS to OS just to eliminate the bulb as the culprit?

I'll try that, will have to pluck up some enthusiasm. Taking the engine out is more straightforward than dealing with the rear bulbs in these cars

[taiwan740]

Originally Posted by john.wigley

Which year / model are we considering, 'taiwan 740'?

It's a 1992, so early model Mark 1.

It's getting the better of me to be honest, considering just getting rid of it. It first failed the MOT in March, so I've been without a vehicle and awaiting repair for two months now.

[Laird Scooby]

^^^^^ What John and Kelvin said!

The offside rear fog MUST work for the MoT in the UK, if the NS is working then it shows the fuse is ok and therefore the wiring and/or bulb and holder are the prime suspects.

Should be 21W bulb..............

[Forrest]

The MOT requirement is for

1 rear fog lamp which must be fitted to the centre or offside of vehicles first used on or after 1 April 1980

Some 900 series cars originally came with just an offside fog lamp and the nearside blanked off. However, any replacement lamp clusters are likely to have a viable bulb holder fitted and many owners connect up the optional nearside one as the wiring is there.

If you’ve got a means of testing for +12V then check the colour-coding of the wire on the working side and test the corresponding wire on the other side. That will narrow it down to cable or fitting.

Check the wire is securely attached to the correct terminal on the cluster.

Possibly, temporarily, sling a piece of wire across from the working side to the non-working side if the fault is in the cable. Maybe even take the car for its MOT like that if it enables you to get it working.

I think from memory the wire runs first to the nearside (these cars were designed in continental Europe) and then across to the offside by virtue of two wires joined in the nearside spade connector. I have seen this join fail, especially if someone has previously made an amateurish attempt at installing towbar wiring.

Good luck sorting it out. In the scheme of things this doesn’t sound a major problem to resolve.

[Laird Scooby]

Originally Posted by Forrest

The MOT requirement is for

1 rear fog lamp which must be fitted to the centre or offside of vehicles first used on or after 1 April 1980

Some 900 series cars originally came with just an offside fog lamp and the nearside blanked off. However, any replacement lamp clusters are likely to have a viable bulb holder fitted and many owners connect up the optional nearside one as the wiring is there.

If you’ve got a means of testing for +12V then check the colour-coding of the wire on the working side and test the corresponding wire on the other side. That will narrow it down to cable or fitting.

Check the wire is securely attached to the correct terminal on the cluster.

Possibly, temporarily, sling a piece of wire across from the working side to the non-working side if the fault is in the cable. Maybe even take the car for its MOT like that if it enables you to get it working.

I think from memory the wire runs first to the nearside (these cars were designed in continental Europe) and then across to the offside by virtue of two wires joined in the nearside spade connector. I have seen this join fail, especially if someone has previously made an amateurish attempt at installing towbar wiring.

Good luck sorting it out. In the scheme of things this doesn’t sound a major problem to resolve.

If memory serves, it was the 1995/6 onwards cars that only had the single rear fog light. Volvo had caught on to the cheapskate French idea of fog one side, reverse the other and just use different colour lenses.
Easy enough to convert to twin rear fog on later cars or remove the blank on lights from later cars when fitting to early cars.

With the OPs car being a 1992, it would have left the factory with twin rear fogs so it would be useful to know if the NS lamp operates.

[taiwan740]

If I gain some enthusiasm I might try swapping the rear bulb. It's failed for a number of things again, though. I'm leaning strongly towards getting rid of it one way or another pretty soon. Probably scrapping it.

It needs welding again, about a four inch square hole in the chassis rail next to the fuel filter. I have just shelled out for the inner front wings to be welded up and had to wait six weeks for that to be done, so I can't really afford to have to wait that long again without a vehicle.

Since I took it in for the MOT (they also replaced the front track rod ends), the ABS light comes on with the self-check. The connectors seem fine. I have no idea, honestly I've lost hope.

The speedo doesn't work at all. I thought I had a replacement but the replacement is for a Mark 2 Volvo and not compatible.

The drivers seat lumbar support is collapsed and the leather ripped to shreds.

The rear central brake light relay has an intermittent fault which managed to activate during the MOT so they failed it for that too.

Urgh, I can't afford the time or space to keep a car insured and taxed but isn't roadworthy. It's been off the road now for two months.

[Laird Scooby]

Originally Posted by taiwan740

If I gain some enthusiasm I might try swapping the rear bulb. It's failed for a number of things again, though. I'm leaning strongly towards getting rid of it one way or another pretty soon. Probably scrapping it.

It needs welding again, about a four inch square hole in the chassis rail next to the fuel filter. I have just shelled out for the inner front wings to be welded up and had to wait six weeks for that to be done, so I can't really afford to have to wait that long again without a vehicle.

Since I took it in for the MOT (they also replaced the front track rod ends), the ABS light comes on with the self-check. The connectors seem fine. I have no idea, honestly I've lost hope.

The speedo doesn't work at all. I thought I had a replacement but the replacement is for a Mark 2 Volvo and not compatible.

The drivers seat lumbar support is collapsed and the leather ripped to shreds.

The rear central brake light relay has an intermittent fault which managed to activate during the MOT so they failed it for that too.

Urgh, I can't afford the time or space to keep a car insured and taxed but isn't roadworthy. It's been off the road now for two months.

Fix the rear fog and take it somewhere else for MoT - before you do, pop the cover off the 3rd brake light bulb, clean and tighten the connectors to the unit and on the bulb, refit and i reckon you'll have solved the problem as there is no relay for the 3rd brake light. There is a rear Bulb Failure Unit which may be giving problems but if the 3rd brake light isn't working intermittently, chances are the connections need cleaning/tightening.

Your car is on the changeover between Bosch ABS and ABS-2E, either way, the ABS warning light is meant to come on during self-check, either it goes out when started (ABS) or after 6-8 seconds (ABS-2E) but either way should be out with the engine running and alternator charging. As such, it sounds like it's behaving itself as it should be.

Does your replacement speedo even look the same? The difference is in the tripmeters and odometers. Yours being a 1992 has a unique speedo/instrument cluster so needs the correct year and just for fun, they had a high failure rate that year!

I'm concerned that "it needs welding again" - if it only took 6 weeks for another hole to appear then either they missed it the first time (unlikely), spotted it the first time and thought "we'll fail it again on that!" (very likely, especially if they offered to take the car off your hands) or your car is rotting at such a rate, if you wait another 3 weeks you can sweep it up and not worry about having to scrap it - highly unlikely!

As i said above, fix the rear fog and 3rd brake light (which shouldn't be a fail if it's not working at all, only if it's intermittent) and get the patch on the chassis welded up and put it in for a test at a different garage.