The Morbidmobile Blog

[TomSaintJames]

I've had a look at the fuse board this morning - the plot thickens!

There was no fuse in the daytime running light (23) or rear fog light (25) positions. All other fuses here appear to be healthy and the correct wattage. Why, you ask? Well...

With a fuse in position 23, the daytime running lights work, which is good. However, so do the tail lights and the green 'headlight on' light is illuminated on the dash - so basically the sidelights are on with a fuse here. Interesting.

With a fuse in position 25 and the headlights and foglight switch on (the little red light now works), ONE of the rear fog lights works but also only one of the tail lights works, these are both on on the passenger side. Now would this have something to do with one of the number plate lights being disconnected? The two rear light units seem to be connected by a few different wires, at least one of which looks like it includes the numberplate lights in the circuit. I won't know I suppose until my replacement units arrive hopefully in the week. Could this be an earth issue instead/aswell?

I've not had a real look at the wires by the hinges, but one does squeak and rub when the tailgate is opened.

Test lamp bought - good idea that, it'll have many uses in the future i'm sure.

[Laird Scooby]

Originally Posted by TomSaintJames

I've had a look at the fuse board this morning - the plot thickens!

There was no fuse in the daytime running light (23) or rear fog light (25) positions. All other fuses here appear to be healthy and the correct wattage. Why, you ask? Well...

With a fuse in position 23, the daytime running lights work, which is good. However, so do the tail lights and the green 'headlight on' light is illuminated on the dash - so basically the sidelights are on with a fuse here. Interesting.

With a fuse in position 25 and the headlights and foglight switch on (the little red light now works), ONE of the rear fog lights works but also only one of the tail lights works, these are both on on the passenger side. Now would this have something to do with one of the number plate lights being disconnected? The two rear light units seem to be connected by a few different wires, at least one of which looks like it includes the numberplate lights in the circuit. I won't know I suppose until my replacement units arrive hopefully in the week. Could this be an earth issue instead/aswell?

I've not had a real look at the wires by the hinges, but one does squeak and rub when the tailgate is opened.

Test lamp bought - good idea that, it'll have many uses in the future i'm sure.

Starting with this bit -

"There was no fuse in the daytime running light (23) or rear fog light (25) positions. All other fuses here appear to be healthy and the correct wattage. Why, you ask? Well...

With a fuse in position 23, the daytime running lights work, which is good. However, so do the tail lights and the green 'headlight on' light is illuminated on the dash - so basically the sidelights are on with a fuse here. Interesting."

The tail lights come on with the DRLs on a 1988 740 Tom so all good - so do the dash lights and the green tell-tale sidelight on the dash. That's one fault fixed!

Next bit "With a fuse in position 25 and the headlights and foglight switch on (the little red light now works), ONE of the rear fog lights works but also only one of the tail lights works, these are both on on the passenger side."

Sounds like you have a bad earth on the right hand side, possibly the left as well. It's also possible someone has interposed the feed and earth wires on one of the bulbholders and it was blowing those fuses that were missing.

Either wedge the brake pedal down (ignition off) to check the brake lights work or better still, get your other half in the car and get him to hit the brakes (ignition still off). Observe the brake lights, particularly their intensity.

Now start the car - the tail lights should come on, all 4 of them and the light should be even intensity across all 4 of them. Now get him to hit the brakes - the outer pair should get much brighter - if any lights dim, make a note of which ones, it will be a valuable clue later!

If all is well, switch the headlights on to dipped beam. The tail lights should remain the same - now add the brake lights to the party. If all is good, let go of the brakes and add the fogs. Observe and note the lights again. Now get your OH to hit the brakes again and once more, observe and note the lights.

Final check is to repeat all the above with each indicator running and then the hazards, then repeat with indicators/hazards off but reverse lights on and finally reverse and indicators/hazards. Don't try and shortcut the indicators by testing the hazards only, this can mask problems which will only show up in the MoT test anyway.

Once you report back, i can hopefully point you straight to the fault, or at least somewhere very close. Also try swapping the fog light bulbs over to see if the fault moves.

If memory serves correctly, the number plates are fed from the left hand side of the sidelight circuit so that ties in with what you've found so far.

[TomSaintJames]

Thanks for all that Dave, i'll wait until I've got the replacement numberplate light unit, just incase that is a break in the circuit, then will perform all the checks. I've written a list of combinations and expected outcomes, i'm sure the other half will be game for some switch flicking!

It's frustrating to have it sat here with no MOT, with one numberplate light holding it back (and maybe other lights too)!

On another note, after running it yesterday I think it is the exhaust manifold that's making the ticking noise when cold - it's much quieter when the engine is warm. My BX GT did this too back along, another that has a known weak manifold in places.

[Laird Scooby]

Originally Posted by TomSaintJames

On another note, after running it yesterday I think it is the exhaust manifold that's making the ticking noise when cold - it's much quieter when the engine is warm. My BX GT did this too back along, another that has a known weak manifold in places.

You're welcome Tom - as for the manifold blow (which it sounds like you have) make sure the engine is nice and hot when it goes for MoT - if needs be take a day off work, book it in for whatever time you like that will guarantee it goes straight onto the MoT ramp and take it for as long a drive as possible before taking it in to get the exhaust nice and hot so it seals better.

[Stephen Edwin]

Can you fix the exhaust manifold "problem"?

Is it the gasket, the tightening of the fixings, the structure of the manifold....

[TomSaintJames]

I'm guessing it's split somewhere that's less than visible, only guessing mind - i've not looked properly. Can't hurt to try tightening the fixings I suppose!

[Laird Scooby]

Originally Posted by TomSaintJames

I'm guessing it's split somewhere that's less than visible, only guessing mind - i've not looked properly. Can't hurt to try tightening the fixings I suppose!

Did you renew the front pipe when you did the exhaust Tom, i can't remember?

If so, run the engine until hot then slacken the manifold to downpipe nuts 1/4 turn and retighten - do them one at a time so the others don't have a chance to break any seal they have formed.

Do similar with any other joins you think are blowing, you can feel by carefully putting your hand near them with it hot and running.

I have a sneaking suspicion that the exhaust manifold is cracked though, allegedly not uncommon on n/asp red-blocks but i've not had one go so can't be sure if it is common or not.

[classicswede]

I have only ever seen one cracked manifold on a NA redblock so it is VERY rare issue. The blow is most likely going to be on a gasket

[TomSaintJames]

Downpipe wasn't done in the end - I didn't have time before our holiday. I think i'll ask the garage to do it when it goes in for MOT.

Good news! Cleaned up the replacement numberplate light unit, and hey presto! The lights now work as they should, except for one fog and the bumper lights when the boot is closed, but this isn't an MOT issue (I hope?!), so i'll see if I can book it in for a super quick MOT at the garage around the corner, not my preferred but when driving with no MOT it's the most sensible option.

Thanks for the advice as always everyone. Broken phone, and my OH smashed the lens in his SLR = no picture taking devices, hence lack of photographic evidence.

[Laird Scooby]

Originally Posted by TomSaintJames

Downpipe wasn't done in the end - I didn't have time before our holiday. I think i'll ask the garage to do it when it goes in for MOT.

Good news! Cleaned up the replacement numberplate light unit, and hey presto! The lights now work as they should, except for one fog and the bumper lights when the boot is closed, but this isn't an MOT issue (I hope?!), so i'll see if I can book it in for a super quick MOT at the garage around the corner, not my preferred but when driving with no MOT it's the most sensible option.

Thanks for the advice as always everyone. Broken phone, and my OH smashed the lens in his SLR = no picture taking devices, hence lack of photographic evidence.

I think what i'd do is put the downpipe in the car, tell them if it needs it for the MoT to fit it, if not you'll fit it sometime later (like next year when it's spring/summer again unless you have to fit it beforehand) and have a go at getting that rear fog going unless it's the left hand one that isn't working. If it's the left hand fog light not working, remove the bulb and tell them it wasn't wired/fitted but you might retro-fit one later. The left one wasn't fitted on all cars, even when it looks like they have a lens for them.

They can't fail it on what wasn't originally fitted!

Talking of which, the bumper lights wouldn't have been fitted originally. I don't think it's a failure the bumper lights go off when the tailgate is down as the normal rear lamps are on the tailgate. I could be wrong, it's something i've never needed to know so my knowledge on that is zero i'm afraid. The fact they weren't original factory lights would be a good argument there as well.

Bit concerned about your phone AND your OH's camera lens BOTH being broken!

Have your devices been trying to consummate their own relationship and in so doing ducked themselves?