Interesting fault to report

[Samuel2709]

Hi all,

I’m new, so please be gentle!

So, I’ve dived into the world of Volvo ownership! Needed to reclaim some of those lost MPG on my big petrol 4x4, so I bought a lovely 2004 manual D5 V70 for the princely sum of £550.

It needs a new DMF amongst other things, but it’s completely drive-able. Well, it was...

I was driving home on Tuesday after work through a 20-zone and noticed a rattle from the back of the car. I pulled over to find that the rear drivers side caliper was a little loose on its slide bolts, but it wasn’t coming off (plastic retaining caps) so I thought that I’d fix it when I got home.

Anyway, as I pulled onto the A14 getting up to speed, I noticed that the SRS airbag service urgent message appeared. I had this deleted about a month back, but it’s clearly reared it’s ugly head once again.

A second later, the brake failure stop safely message flashed up for a whole further second, and then I noticed that all the dials had stopped moving.

3 seconds later, the entire dash went completely blank. Nothing. So I thought, I best check nothing else has broken. Tried the windows - nothing. Tried the indicators - nothing. Tried the brake lights *panics* - nothing.

I couldn’t select mirrors, I couldn’t adjust any windows about the car, I had no dash, and all lights had stopped working.

Pulled over in blind panic, and turned the engine off. Back on,all was well, and on the move. 4 seconds later - exactly the same thing.

Now, I know most people might say DIM - I have read the failure scenarios and understand the fix is a case of resoldering the dash (yay!). But I had 0 loss of power, and everything else worked. Brake servo was fine, engine was fine, radio all worked, the passengers window worked fine, it was just all of the drivers side things that decided to die.

Note - the fault disappears when the ignition is cycled, suggesting a fuse (unless resettable on the PCB) isn’t to blame.

Got home, and plugged in OBD. Read a P0600 fault (serial comms fault) so I cleared this, and took the car for a 2 mile drive. Got it up to speed, and all was well.

Anyone got any ideas? Any help would be very much appreciated. I have a weird theory that the rattling caliper may have thrown an ABS fault just at the moment the SRS airbag fault wasn’t initiated, and that caused the total shutdown of all drivers-side ancillaries.

[reggit]

Check the battery terminals are making a good connection and are tight.
Also check the engine earth strap hasn’t gone weak at the terminal on the starter motor. They tend to fray inside the rubber sheath and give interesting issues until they completely part company and the car won’t start.

[Wagon Sailor]

Our 240 occasionally does that thing when none of the dash, windows, indicators etc work. We found out that it happens when we turn the key a little too far on starting. I guess that the barrel's worn.

[oragex]

As above, low alternator charging or battery may cause random things and it's the first thing to verify. Unfortunately, a 2004 has another weak spot, the CEM water ingress

[Samuel2709]

Hi all,

Thank you kindly for your thoughts; I hadn't even considered a dodgey earth strap! Stupid really, as I am an electrical engineer. Wood through the trees me thinks...

I will check the earth terminals using a meter for their continuity. I will also look for fraying or filthy terminations.

I will also check the ignition barrel, however, I haven't noticed it feeling strange when starting the car.

I love a free fix! Lets hope and pray for crappy earthing....

Originally Posted by oragex

As above, low alternator charging or battery may cause random things and it's the first thing to verify. Unfortunately, a 2004 has another weak spot, the CEM water ingress

Whats a CEM?

Thank you all

[cheshired5]

Originally Posted by Samuel2709

I will check the earth terminals using a meter for their continuity

A continuity test will be no good.
You need to do voltage drop tests on high current cables.

[Samuel2709]

Originally Posted by cheshired5

A continuity test will be no good.
You need to do voltage drop tests on high current cables.

Ah, do you mean like a flash test?

I work with the equipment, so this won't be an issue. I shall look further into it

[cheshired5]

Originally Posted by Samuel2709

like a flash test?

No idea what that is.

Set the meter to DC volts, red lead on the earth strap bolt at the starter motor/engine block, the black lead on the earth strap bolt on the chassis and read off the highest voltage during cranking and report back.

Do several tests and manipulate the earth strap joints before each one to see if the reading changes.

[Samuel2709]

Originally Posted by cheshired5

No idea what that is.

Set the meter to DC volts, red lead on the earth strap bolt at the starter motor/engine block, the black lead on the earth strap bolt on the chassis and read off the highest voltage during cranking and report back.

Do several tests and manipulate the earth strap joints before each one to see if the reading changes.

Hi cheshired5,

My apologies; I have been busy with work so I didn't find a chance to respond!

I intend on testing the V-drop tonight; I did some basic preliminary investigatory work on Sunday evening and found a few odd-balls.

There is a fused small-gauge wire (possibly 0.5mm2) running off of the positive terminal of the battery. It goes under the rear seats and then I lost it, so I removed the fuse and nothing has stopped working as far as I can see.

I also found 2 fused wires that have been spliced into the loom behind the large fuse board behind the drivers door. They come from the 12v main supply, and are fused at 2a. One was blown, but I should have removed the good one to see what stopped working.

Thank you!

PS flash test is also known as an insulation resistance test; http://www.flashtesting.co.uk/ - boring safety stuff...

[palwing]

Didn’t we used to just use a megger with a windy handle to test insulation breakdown?

Oh, and shock adjacent engineers!