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[LC0112G]

I'd, be checking the earth strap's, as they corrode,

Do you mean the engine earth strap? How does that blow F15?

48 hour since I unplugged the rear level sensor (K21) (and rear heated seat switches) and so far no more fuses blown. If it survives tomorrow then weather permitting I'll be taking the sensor off on Sunday to bench test it next week.

[biggriffin]

I'd, be checking the earth strap's, as they corrode,

Do you mean the engine earth strap? How does that blow F15?

48 hour since I unplugged the rear level sensor (K21) (and rear heated seat switches) and so far no more fuses blown. If it survives tomorrow then weather permitting I'll be taking the sensor off on Sunday to bench test it next week.

 Reason I say, is on my last 3.0L it kept blowing the, big 30a one under bonnet, would be fine for couple of days,then stop,, took me weeks, turned out the earth strap's were corroded, and sparking, removed them, cleaned and refitted, no more problems,,.

Ps, I might have a rear suspension level sensors.

[biggriffin]

^^^^^yup got one. Check for sales

[LC0112G]

Sitrep...

Fuses kept blowing at intervals from 10 minutes to 1 hour. Rear level control unplugged, radio out, rear seats unplugged, OSF headlamp levelling unplugged. So I replaced the fuse with the ammeter and went for a drive. Everything normal for about 30 minutes - then smoke from the AVO and it's leads. Current reading was over-range on the 20A range. Quickly pulled the leads out of the AVO and went home. 

Replaced the fuse, and it blew immedatley. Removed the battery and put the AVO in to measure resistance from the cold side of F15 to ground. Success - of sorts. I'd now got a permanent short to ground. Unplugged all the relays in the under-bonnet fusebox. Still short to ground. Then looked again at Haynes.

The loom appears to be in 3 sections - Engine bay, Dash and Body. The fuse is in the dash, so part of the dash loom. The connection to the body is via connector X1. The connection to the engine bay is via connector X5. I should be able to isolate the 3 sections of the loom by unplugging these connections. That would tell me which section of the loom, and therefore which units, might be faulty.

So easiest first X5, which AIUI is one of the 3 circular connections next to the battery. I couldn't decide which of the 3 though, so I unplugged them all. AVO short still present. So that rules out any wiring or units down stream of X5.

Next X1, which I think is the long thin connector behind the kick panel in the drivers foot-well (behind the bonnet release lever). Unplugged that - short still present.

So it appears the fault is in the dash somewhere. Radio already out, so not that. Took the instrument binnacle out. Fault still present. Glovebox out. Fault still present. Dropped the fusebox for a looksee - wiring all looks Ok and nothing there that looks like it shouldn't be. Pulled the facia off to get at the back of the climate control, and unplugged the two plugs - Short goes away. Hmmm.

So the current thinking is its either....

1) Faulty CC panel
2) Faulty CC servo or solenoid
3) Faulty (dash?) wiring that I've disturbed by unplugging all the stuff.

Personally, I'm suspecting the dash wiring, but no amount of pulling, pushing, jiggling or wiggling of the various wires and connectors could get the fault to re-occur.

So I've plugged the power lead back into the CC (so the blower still works for demisting), and left the second plug (to the CC servos/Solenoids) unplugged. Then put everything else back together, replaced the fuse and went for a drive.  So far everything is Ok, although I haven't done any trips longer than 20 minutes yet. Got to go to the Bristol ABS meeting tomorrow, and probably Harwell sometime later this week too.     

[Andy B]

 

[STEMO]

I do hope you find this fault, Malcolm, because you certainly deserve to.  If you're looking for a silver lining, just think of all the stuff you've learned about how an omega is put together 

[Doctor Gollum]

The dash plugs into the body loom via a large blue and large black plug behind BOTH kick panels. If the drivers side is OK, try the passenger side.

There's also a loom that runs across the floor between the plugs.

[LC0112G]

Drove to Harwell and back today. Fuse popped at the A303/A34 junction on the way up. Replaced it at Tot Hill Services (just after my Double Sausage McMuffin and Bacon Roll brekkie), but it popped again before the M4.

Spent all day in a pointless meeting at Harwell, and replaced the fuse at about 6:30pm before heading off home. Fuse popped again at the A34/A303 junction. It obviously doesn't like that junction! CBA to stop on the way home, plus the A303 is closed overnight at 8PM near Wincanton, so needed to get past that before it shut.

Once safely past Wincanton, started experimenting. When Fuse F15 pops, the alternator/charge/ignition lamp comes on. I'd noticed in the past that sometimes it is half bright, and sometimes full bright, and it can 'wink' between the two. Tonight's experiments revealed that it tends to be full bright when turning left, and half bright when turning right. It was quite repeatable. This is all while travelling at 70 (ish) just taking the bends on the A303. I was starting to suspect the headlamp levelling, since presumably the sensors will detect the slight ducking and diving of the front of the car during cornering.

Next check was on the dual carriageway sections. I tried lifting and wiggling and pushing and twisting the steering wheel/column - without actually turning the wheel. Sure enough I could make the alternator/charge/ignition lamp change between half and full bright. Hmmm. This is making me think it might be the steering wheel/column fouling/trapping/shorting some wires behind the dash. What I don't know is if it's the full bright or half bright alternator/charge/ignition lamp condition that occurs during the short. Suspect it's half bright. Anyway, assuming it's not normal behaviour it's got to be worth a look along/around the steering column area.

Second problem is I appear to have smoked my AVO doing last weekends tests. It doesn't seem to have liked >20A going through it.

[Darius]

I hate intermittent faults - they drive anyone to insanity.

One thought.  You say the sun roof does not work.  This may be because it needs resetting after the battery was disconnected.  Reset instructions are in the manual or I could upload mine (2.2 DTI).  It could be the source of the fault but because it "doesn't work" you are not testing it.

[Darius]

Another thought.  Can you insert extra fuses after F15 but as close as possible to where the wiring splits off for the circuit?  Or is access too difficult?

Say F15 powers 5 circuits.  Insert smaller fuses (10A?) as close as possible to F15 but in each of the 5 circuits. 

If only F15 blows it is in the wiring before any of the other fuses or you have missed a sixth circuit. 

If any of the other fuses blows it is that circuit. 

It could help to isolate the problem by eliminating "good" circuits.

A complication is the fuses are in series with the larger F15 but if you set F15 to 30A and the others to 10A it is likely the 10A will blow before F15 blows.

I have been trying to think of a way of using the return current to the battery (it must be over 20A) to identify the region in the bodywork it flows through but I think and voltage drop it would be too small to be useful.

[LC0112G]

Another thought.  Can you insert extra fuses after F15 but as close as possible to where the wiring splits off for the circuit?  Or is access too difficult?

Say F15 powers 5 circuits.  Insert smaller fuses (10A?) as close as possible to F15 but in each of the 5 circuits. 

If only F15 blows it is in the wiring before any of the other fuses or you have missed a sixth circuit. 

If any of the other fuses blows it is that circuit. 

It could help to isolate the problem by eliminating "good" circuits.

A complication is the fuses are in series with the larger F15 but if you set F15 to 30A and the others to 10A it is likely the 10A will blow before F15 blows.

I have been trying to think of a way of using the return current to the battery (it must be over 20A) to identify the region in the bodywork it flows through but I think and voltage drop it would be too small to be useful.

)
F15 powers about 20 circuits. That's why it's been so tricky to debug. But yes, I have tried a version of your idea, and will try more once the gearbox is in (hopefully Friday)

So far I've isolated the dash/instrument binnacle, and powered it of it's own fuse. At least that means what when F15 blows I don't lose speedo, eng temp, rev counter and fuel gauge which was threatening to get me a speeding ticket! And F15 does still blow, so that rules out the instrument cluster as being the fault.

At the moment, the headlight levelling ECU, glove-box, sunroof and rear heated seats are unplugged - so not them.

I have previously unplugged the level control sensor plug (OSR trailling arm), radio, climate control panel, MID, underbonnet fusebox fan, Cruise Control, courtesy lights, drivers door window control switches, and light switch. F15 has continued to blow with these things disconnected.

Therefore  there is either something else taking it's power from F15 that I'm not aware of, or it's a short in the wiring. As far as I can tell, all the 'body' systems get their F15 power via connector X1-pin49. All of the 'engine bay' systems get their F15 power via connector X5-pin1.

The plan at the moment (once the gearbox and exhaust are back on) is to locate these connectors and try to isolate these pins. Ideally I'd like to pull the pins out of the connector, but I doubt I'll have the correct pin extraction tools. So if that fails, much as I dislike wiring bodges, I'll have to snip the wires close to the connectors and bodge-wire in fuses - probably 5A. Then if either of new 5 A fuse blows, I'll know the fault is downsteam of either the 'body fuse' or 'engine bay fuse'. If F15 still blows then it's pointing towards the wiring in the dash.

I don't think there is much point speculating on the cause now until I know which of the 3 fuses blows.

[Doctor Gollum]

Another thought.  Can you insert extra fuses after F15 but as close as possible to where the wiring splits off for the circuit?  Or is access too difficult?

Say F15 powers 5 circuits.  Insert smaller fuses (10A?) as close as possible to F15 but in each of the 5 circuits. 

If only F15 blows it is in the wiring before any of the other fuses or you have missed a sixth circuit. 

If any of the other fuses blows it is that circuit. 

It could help to isolate the problem by eliminating "good" circuits.

A complication is the fuses are in series with the larger F15 but if you set F15 to 30A and the others to 10A it is likely the 10A will blow before F15 blows.

I have been trying to think of a way of using the return current to the battery (it must be over 20A) to identify the region in the bodywork it flows through but I think and voltage drop it would be too small to be useful.

)
F15 powers about 20 circuits. That's why it's been so tricky to debug. But yes, I have tried a version of your idea, and will try more once the gearbox is in (hopefully Friday)

So far I've isolated the dash/instrument binnacle, and powered it of it's own fuse. At least that means what when F15 blows I don't lose speedo, eng temp, rev counter and fuel gauge which was threatening to get me a speeding ticket! And F15 does still blow, so that rules out the instrument cluster as being the fault.

At the moment, the headlight levelling ECU, glove-box, sunroof and rear heated seats are unplugged - so not them.

I have previously unplugged the level control sensor plug (OSR trailling arm), radio, climate control panel, MID, underbonnet fusebox fan, Cruise Control, courtesy lights, drivers door window control switches, and light switch. F15 has continued to blow with these things disconnected.

Therefore  there is either something else taking it's power from F15 that I'm not aware of, or it's a short in the wiring. As far as I can tell, all the 'body' systems get their F15 power via connector X1-pin49. All of the 'engine bay' systems get their F15 power via connector X5-pin1.

The plan at the moment (once the gearbox and exhaust are back on) is to locate these connectors and try to isolate these pins. Ideally I'd like to pull the pins out of the connector, but I doubt I'll have the correct pin extraction tools. So if that fails, much as I dislike wiring bodges, I'll have to snip the wires close to the connectors and bodge-wire in fuses - probably 5A. Then if either of new 5 A fuse blows, I'll know the fault is downsteam of either the 'body fuse' or 'engine bay fuse'. If F15 still blows then it's pointing towards the wiring in the dash.

I don't think there is much point speculating on the cause now until I know which of the 3 fuses blows.

Notwithstanding that any of the wiring between fuse 15 and the unplugged plugs could be faulty... 

[STEMO]

Post up a pic of your omega when it looks like Al's trolley, in a thousand pieces 

[LC0112G]

Notwithstanding that any of the wiring between fuse 15 and the unplugged plugs could be faulty... 

True, but if I can isolate the fault to 'body', 'dash' or 'engine bay' then at least that narrows down the sections of loom that need inspecting.

[Doctor Gollum]

Post up a pic of your omega when it looks like Al's trolley, in a thousand pieces 

That's the Trolley replacement  if the Vectra C give Terry nightmares, he probably shouldn't get an S Class