Information Electrical - A2 earth points

[Howey]

Just tried removing the alternator belt in case the tensioner/alternator/air con pump are seized up but all 3 were fine turning easily by hand, dont know where else to check, when cranking the engine, the voltage drops & the earth wire on the battery pack very warm.

No idea where else to look !

What exactly have you done with the earth?
You could try running a earth from the battery to the engine block?

 

[Ami]

What exactly have you done with the earth?
You could try running a earth from the battery to the engine block?

I have taken an earth all the way from battery -Ve to the starter motor body, but no change, still cranks very weak as a result of possible short circuit etc hence battery voltage falls to 5.5 volts.

 

[Ami]

I also tried the earth behind the headlight, looked corroded and sure enough it snapped, so put a new longer earth cable from starter to one of the 3 bolts on the chassis the passenger sided leg

 

[Howey]

I have taken an earth all the way from battery -Ve to the starter motor body, but no change, still cranks very weak as a result of possible short circuit etc hence battery voltage falls to 5.5 volts.

Thats very strange!

I also tried the earth behind the headlight, looked corroded and sure enough it snapped, so put a new longer earth cable from starter to one of the 3 bolts on the chassis the passenger sided leg

i tried adding an earth their and it didnt work at all instead used the engine mount to aux belt tensioner but you say you have gone direct so earth cannot be the issue.
Folks have had issues with wiring to ac compressor and oil level sensor but thats me scrapping the barrel!
Will ask our auto electrians tomorrow see if they can think of anything!

 

[Ami]

Thats very strange!
i tried adding an earth their and it didnt work at all instead used the engine mount to aux belt tensioner but you say you have gone direct so earth cannot be the issue.
Folks have had issues with wiring to ac compressor and oil level sensor but thats me scrapping the barrel!
Will ask our auto electrians tomorrow see if they can think of anything!

Thank you very much for your help

 

[Catnip64]

Hi:
do you have a picture of this, I am having a lot trouble with what seems to be a short circuit across +ve & -ve upon cranking the engine, the battery voltage drops from 12.8 volts down to 5.5 volts, have replaced, starter, cable behind headlight, battery. Have had lots of advice with thanks to @audifan but just can not locate the short circuit, it happens upon cranking the ignition/engine as mentioned, which stops the car from starting. it was hard to start but gradually got worse, I can put two batteries in parallel & start the car, but even that not always work.
Maybe a Relay somewhere causes the short when turning the ignition, its doing my head in.
Cheers,
Ami

You've changed almost all of the parts associated with the starter circuit, so it seems as though the 'short' may be on another circuit, but only presents when cranking the engine. I assume that once the engine has started, the battery voltage is normal and that the alternator functions correctly?
If that's the case what you could try is to remove the solenoid feed on the starter and then measure the voltage at the battery when turning the key to the cranking position. If it still drops to 5.5V then the 'short' is not the starter and you can investigate the other circuits that are energised when the key is in this position.

 

[Ami]

You've changed almost all of the parts associated with the starter circuit, so it seems as though the 'short' may be on another circuit, but only presents when cranking the engine. I assume that once the engine has started, the battery voltage is normal and that the alternator functions correctly?
If that's the case what you could try is to remove the solenoid feed on the starter and then measure the voltage at the battery when turning the key to the cranking position. If it still drops to 5.5V then the 'short' is not the starter and you can investigate the other circuits that are energised when the key is in this position.

Thanks for your reply, I haven't checked the battery voltage when the engine was running, I will have another attempt tomorrow, never seen anything like it in 44 year driving,

 

[spike]

Although battery earth faults are most common it must also be possible to have problems with the battery positive supply. A high resistance in the cable or terminal connections could possibly cause the big voltage drop seen when cranking.
I've not checked the feasibility but would it be possible to run a positive cable direct to the starter to eliminate faults with the main feed.
Great care would be needed with the connections to avoid any risk of shorting, particularly due to relative movement / engine rock if it fires up.

Cheers Spike

 

[Catnip64]

Although battery earth faults are most common it must also be possible to have problems with the battery positive supply. A high resistance in the cable or terminal connections could possibly cause the big voltage drop seen when cranking.
I've not checked the feasibility but would it be possible to run a positive cable direct to the starter to eliminate faults with the main feed.
Great care would be needed with the connections to avoid any risk of shorting, particularly due to relative movement / engine rock if it fires up.

Cheers Spike

My thoughts as well Spike, but Ami said battery voltage was 5.5V, so I ruled this out but perhaps the drop was indeed measured at the starter? Perhaps Ami could confirm.

 

[Ami]

Although battery earth faults are most common it must also be possible to have problems with the battery positive supply. A high resistance in the cable or terminal connections could possibly cause the big voltage drop seen when cranking.
I've not checked the feasibility but would it be possible to run a positive cable direct to the starter to eliminate faults with the main feed.
Great care would be needed with the connections to avoid any risk of shorting, particularly due to relative movement / engine rock if it fires up.

Cheers Spike

Thanks for your input Spike, I actually have tried running a direct cable from battery positive & negative to the starter, using a very heavy duty long pair of jump leads, my friend was under the car while doing this, He said a lot of sparking at the starter motor.
I am wondering what could cause a short circuit across +ve & -ve when cranking.

 

[Ami]

My thoughts as well Spike, but Ami said battery voltage was 5.5V, so I ruled this out but perhaps the drop was indeed measured at the starter? Perhaps Ami could confirm.

Thanks , I actually measured volt drop at the battery end while cranking, it started with 2 batteries in parallel, last night I put 4 batteries in parallel, struggle was less, but never started, the -ve of the second battery on the row got very warm upon cranking.
The massive volt drop was still there even with 4 batteries in parallel , god knows what could be shorting & not burning out.

 

[Ami]

Once I get 5 minutes, I will try to write the series of event leading to this issue, maybe someone can see what I am missing.
Cheers all
Ami

 

[jonjo]

Is there a best practice guide for tidying up these ground locations?

Shiney metal on both faces as smooth as possible and any kind of grease to prevent further oxidation? I’m guessing this corrosion is galvanic more than ferrous oxidation? Should there be a sensible intermediary grease?

Contact corrosion can occur if unsuitable fasteners (bolts, nuts, washers, etc.) are used.

For this reason, only fasteners with a special surface coating are fitted.

 

[Ami]

As mentioned a brief history of the car issues still no cure:
The A2 came to me from a forum member who had been quoted £950 to get MOT, I got the new MOT using some new some second hand parts with just over £400 , on the way back from MOT station the ABS light came on, I thought I have had this many times before when the car has been sitting for a while.
She then asked me if I could do a service to include cam belt kit as it had not been done in 11 years I did service/cam belt etc and then the car wouldn't start, found a burnt wire on the aerial diversity unit, after checking as much as I could and changing earth cables, starter motor, new battery and much more now she starts.
I turned off the ABS light after cleaning sensor etc, drove round a block it came straight back on, changed the sensor turned off the lights it came back on as soon as I drove out.

My problem now:
1. I can not turn off the ABS light any more as my scanner says no communications
2. The power steering light has also come on
3 The speedo has also stopped working

Many technical forum members have helped with the above via PM, telephone etc, but still no resolution.
Any help/advice is very much appreciate it, I have checked wiring, fuses, relays but no result. also have used 2 other diagnostic tools no communications.

Many thanks,
Ami

 

[kp 115]

Hi Ami,
Have you scanned with VCDS fully licensed ?
Also I believe the electronic section can be separated, if so ECUTESTING.Com have a very good service may be worth having a chat with them.
Hope that helps
Keith.

 

[Ami]

Hi Ami,
Have you scanned with VCDS fully licensed ?
Also I believe the electronic section can be separated, if so ECUTESTING.Com have a very good service may be worth having a chat with them.
Hope that helps
Keith.

Hi Keith:
I also sent the car out to a friend who has full VCDS & He could not establish communications to enable him to turn the lights off.

I will check ECUTESTING.com
Many thanks,

 

[kp 115]

Hi Keith:
I also sent the car out to a friend who has full VCDS & He could not establish communications to enable him to turn the lights off.

I will check ECUTESTING.com
Many thanks,

I’ve used them twice for a Mercedes A160 ecu & a Vauxhall meriva ecu quick turnaround & still running, lifetime warranty!!

 

[Catnip64]

As mentioned a brief history of the car issues still no cure:
The A2 came to me from a forum member who had been quoted £950 to get MOT, I got the new MOT using some new some second hand parts with just over £400 , on the way back from MOT station the ABS light came on, I thought I have had this many times before when the car has been sitting for a while.
She then asked me if I could do a service to include cam belt kit as it had not been done in 11 years I did service/cam belt etc and then the car wouldn't start, found a burnt wire on the aerial diversity unit, after checking as much as I could and changing earth cables, starter motor, new battery and much more now she starts.
I turned off the ABS light after cleaning sensor etc, drove round a block it came straight back on, changed the sensor turned off the lights it came back on as soon as I drove out.

My problem now:
1. I can not turn off the ABS light any more as my scanner says no communications
2. The power steering light has also come on
3 The speedo has also stopped working

Many technical forum members have helped with the above via PM, telephone etc, but still no resolution.
Any help/advice is very much appreciate it, I have checked wiring, fuses, relays but no result. also have used 2 other diagnostic tools no communications.

Many thanks,
Ami

So does the car now start okay and there's no issue with the voltage drop that you saw previously - How did you solve this?

 

[Ami]

So does the car now start okay and there's no issue with the voltage drop that you saw previously - How did you solve this?

Cut off the burnt wire on the diversity amplifier & put a brand new battery.

 

[Guest 4123]

Hi Keith:
I also sent the car out to a friend who has full VCDS & He could not establish communications to enable him to turn the lights off.

I will check ECUTESTING.com
Many thanks,

Hi Ami,

Do you mean any communications with the car or just with ABS? Any error codes?

RAB