I have a 2001 A170 cdi that appears to have an electrical problem. It started the others day. The battery warning light came on (not fully bright as you would expect) and the power steering was lost. The RAC man said it was probably the poly belt and could not be repaired at the roadside. Taken to a local garage that said the belt was ok. They tested the Alternator and battery and said they appear ok (they battery was not perfect but still working ok). When they started the car the light had gone and everything appeared to work. They did change the battery and poly belt just in case. Thought that was the end of it - all electrical systems worked. However, they took the car for a test drive and found that when the car warmed up the problem came back. Battery warning light on and no power steering. They thought it must be the alternator but when they put the tester on it it was ok and was charging the battery. They found that the battery was starting to smell and when they tested the voltage it was 17V - high!. The situation now is when the car is cold. the normal battery voltage is 12.4V and the alternator charge voltage is constant at 14V (sounds normal) but when the car (and alternator) warm up the charge voltage goes up to 17Volts cooking the battery. They assume the problem must be with the alternator. They got what they thought was the replacement alternator (90amp veleo) but when they tried to fit it found that mine was equipped with a 150Amp water-cooled alternator!
Managed to get a Lucas water cooled replacement part from Euro Car Parts for £185. Took about 5 hours to fit! Tested the new unit and all appeared ok until we went for a test drive. The same problem came back - lost of power steering, battery light flickering on the dash.
Just sat with the car on the drive testing a few things out:
-Normal battery voltage 12.4V.
-engine starts firt time
-Alternator cuts in and charge voltage is 14.4V
-turn on headlights, heated windscreen, rear heater, fog lights and the charge voltage drops to about 13.95V
-move steering wheel too and fro - no effect on charge voltage.
-did this for 20 minutes voltage constant +/-0.3V
put foot on brake and put car in reverse then released brake. Car moved back and the battery light came on together with the loss of power steering even though the charge voltage was 14V (and did not even flicker)
-put car in forward - the same
-leave in park then the light goes out and the power steering returns (no change in charge voltage 14V).
-I then reved the engine to around 4K and the battery light came on and power steering off. yet again the voltage was constant at 14V. The light remained on flickering as the revs dropped.
This suggests the alternator is working ok
why does the steering pump cut out when the light is on?
I have also spoken to a Merc engineer who said that it could be either the speed sensor or angle sensor linked to the power steering. He thought that the speed sensor probably gets the signal from the alternator (could this be the blue wire?) He also suggested checking the engine tick-over that this reset properly when the battery was disconnected (sometimes this needs to be recalibrated). He said if the tick over was slightly on the low side then as the engine warmed up the revs would drop slightly causing the issue and when the gears are selected this will lower the engine revs and may trigger the fault. Sounds possible to me. Think I need to get the system reset by the ECU and see what happens.
What do you think?
Any ideas?
Managed to get a Lucas water cooled replacement part from Euro Car Parts for £185. Took about 5 hours to fit! Tested the new unit and all appeared ok until we went for a test drive. The same problem came back - lost of power steering, battery light flickering on the dash.
Just sat with the car on the drive testing a few things out:
-Normal battery voltage 12.4V.
-engine starts firt time
-Alternator cuts in and charge voltage is 14.4V
-turn on headlights, heated windscreen, rear heater, fog lights and the charge voltage drops to about 13.95V
-move steering wheel too and fro - no effect on charge voltage.
-did this for 20 minutes voltage constant +/-0.3V
put foot on brake and put car in reverse then released brake. Car moved back and the battery light came on together with the loss of power steering even though the charge voltage was 14V (and did not even flicker)
-put car in forward - the same
-leave in park then the light goes out and the power steering returns (no change in charge voltage 14V).
-I then reved the engine to around 4K and the battery light came on and power steering off. yet again the voltage was constant at 14V. The light remained on flickering as the revs dropped.
This suggests the alternator is working ok
why does the steering pump cut out when the light is on?
I have also spoken to a Merc engineer who said that it could be either the speed sensor or angle sensor linked to the power steering. He thought that the speed sensor probably gets the signal from the alternator (could this be the blue wire?) He also suggested checking the engine tick-over that this reset properly when the battery was disconnected (sometimes this needs to be recalibrated). He said if the tick over was slightly on the low side then as the engine warmed up the revs would drop slightly causing the issue and when the gears are selected this will lower the engine revs and may trigger the fault. Sounds possible to me. Think I need to get the system reset by the ECU and see what happens.
What do you think?
Any ideas?
