fabia strange electrics

[carmadrob]

do you think vcds lite along with a vag com kkl 409-1 cable will do or do i need the full vcds and ross tech setup, cheers

[TMB]

VCDS lite and that cable should be fine.

Edited 6 December, 2015 by TMB

[carmadrob]

update car still playing up, checked charging system again but need some advice, ive fitted a new alternator- engine running im getting 14.5 ish volts at battery but with meter connected the readings are going from 14.5v then down to 2v instantly then up to 14.5v again in a blink of a eye if you know what i mean, its like im taking meter off for a split second then back on, drops to 2v-7v-8v then back up, should charge be 14.5 v all the time or is it dropping becuase battery is fully charged, any help please, thanks

[Breezy_Pete]

Can you try with a different multimeter?

Alternator should always put out 14.5V or as close to that as it can manage if demand is greater than it can supply at a given rpm.

[carmadrob]

cheers tried that with my mates but still the same

[wiredsoftware]

Tried testing resistance from battery negative to chassis and seeing if it increases when voltage decreases?

[carmadrob]

sorry for being dumb but how do i set up my meter for above, cheers

[wiredsoftware]

sorry for being dumb but how do i set up my meter for above, cheers

 

Set it to Ω/ohms, say 2000Ω. A reading of "1." or ∞ or "infinity" or similar indicates full resistance (you'll see that figure when both probes are apart), 0 is no resistance (you'd see that when you touch both probes together). The figures you get don't matter much, as long as you are seeing a low value close to 0, say about 5. If you're getting an intermittent break to ground side, you'd expect it to briefly jump towards almost 1/infinity before going back to near zero. Be sure to choose a good place on the chassis (bare metal, no rust).

 

Also try the same test, putting the probes either side of the chassis-to-engine earth straps to test each of them.

Edited 14 January, 2016 by wiredsoftware

[Breezy_Pete]

cheers tried that with my mates but still the same

Any chance same mate can lend you his battery temporarily, to swap into your car to rule that out?

[carmadrob]

thanks for meter advice, will try another battery, would a duff battery give me the problems im getting, thanks

[Breezy_Pete]

Not sure TBH. One failure mechanism I've heard of with batteries is that bits of lead drop off the electrodes and fall to the bottom of the plastic case. If that pile of bits gets high enough, it can short out the battery.  I wonder if you're getting shorts that are taking big currents, and burning themselves away again as soon as they happen; giving you that dipping of voltage that recovers.

Sounds pretty far-fetched, I must admit, but if you can borrow a known good battery that'll fit in the box, it's a fairly quick and easy thing to rule out.

[wiredsoftware]

thanks for meter advice, will try another battery, would a duff battery give me the problems im getting, thanks

Yup, could well cause problems.

 

If the resistance tests are OK, you should do some voltage drop tests, even though you're not having starting problems. Lots of info here: http://www.aa1car.com/library/voltage_drop_testing.htm and here 

Edited 14 January, 2016 by wiredsoftware

[carmadrob]

cheers will try tests and swap out battery and post back, been out in the car again and got airbag, power steering-oil light on, no rev counter etc but car still drives ok

[Tech1e]

I'd be looking with VCDS at the CAN network myself. Sounds like you have a network issue, more than likely a faulty gateway/dash cluster.

[carmadrob]

cant swap out cluster because of its got imobiliser built in, damm, i take it gateway is the feed to cluster, i could take out cluster and check connections just to rule that out, ive got vcds lite but will that pull up full diagnosis ?

[Tech1e]

Gateway is the can bus interface. It's part of the dash cluster. If you can access gateway 19 with lite you could try having a look in the measure blocks to see if all can is communicating.

[carmadrob]

swapped out battery but just the same, i ran engine and whilst i was sitting in car which was idling i heard bleeps then looked at dash, temp gauge was on full same for fuel guage, revs dropped to zero, power steering light on, epc light on, then i switched off, started car again and back to normal, tried vcds with vag com cable but pc and ports good but wont communicate with car, tried another diag reader but the same, wont com, with car, doing my head in

[sepulchrave]

Last time I remember seeing these symptoms was after a bad ICE install had bricked various control modules, IIRC it was Aaron Mountford with a Fabia 1.4 16V and he scrapped it subsequently.

[carmadrob]

control modules, if its them then id of thought it would be a permanent fault not random and clear when i switch off and on again , except airbag light, did see somewhere that i can take a fuse out and cluster works but milage zeros when you cycle ignition but cant find topic again lol, going to try the meter test on battery / alternator tommorow for load etc,

[Tech1e]

Sounds like a knackered dash cluster to me.

[carmadrob]

well i managed to run a full vcds scan, loads of faults, i clicked save but when i open vcds log nothing showing, faults where mostly intermitent comm with cluster, low voltage, no comm etc, wished it had saved lol, cleared all codes, fitted new earth from battery to leg, new f16 fuse just in case, fitted new alternator belt, when it or if it plays up again i will run fresh scan and print/save results.

[sepulchrave]

Run autoscan again, click copy, then paste it into a blank text file.