Starter solenoid noise, VW Golf Mk.6

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Re: Starter solenoid noise, VW Golf Mk.6

Postby AWright » Thu Mar 12, 2015 7:44 pm

Just looking at that waveform, is channel C connected to terminal 50 of the solenoid or the switched output of the solenoid to the starter motor ?
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Re: Starter solenoid noise, VW Golf Mk.6

Postby mikehaimes » Sat Mar 14, 2015 7:49 am

You are over analysing the current draw the high amperage draw on initial start is called "in rush current" the amount of current it takes to get the starter moving. Heres 3 different waveforms to prove my point from 3 different vehicles
mercc180kompressor 2003 jumped chain.psdata
(3.24 MiB) Downloaded 111 times
mini cooper 1.6 2008 rel comp.psdata
Good starter current
(854.87 KiB) Downloaded 97 times
mazda demio relative compression vs ignition ttiming.psdata
Good starter current
(1.11 MiB) Downloaded 98 times
If the motor had trouble turning over you would see higher than expect current draw for a lot longer than that. What I invite you to try is put your low amp clamp on the solenoid trigger wire and look for around 10amps + for voltage supply. Here is a bad one
toyota estima starter.psdata
Bad Starter Solenoid Current
(630.66 KiB) Downloaded 118 times
here is a good one
toyota estima starter after replace starter.psdata
Good Starter Solenoid Current
(1.84 MiB) Downloaded 102 times
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Re: Starter solenoid noise, VW Golf Mk.6

Postby sigoaprendiendo » Sat Mar 14, 2015 9:48 pm

Valhalla wrote:... and following starter motor switch-off there is a decaying voltage for approximately 1second before complete shut-off to 0v. So I'm definitely going to try the new starter relay, plus measures around this, before condemning anything else. If this "decaying voltage" pattern is typical of VW's, then it might explain why so many of their products have post-start starter motor hang-up whining problems.


Hi

I think at this point that this voltage values are pretty normal and this 1 second time before shutting off is a natural behavior from the starter acting as dynamo supplying counter EMF as it is still spinning, this EMF goes through the exciter circuit via the pull in coil as the two main internal solenoid contacts are already opened :roll:

Starter.jpg
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Sun Mar 15, 2015 7:35 pm

Many thanks for the replies, sorry it has taken me a couple of days to get back.

In respect of the terminal 50 measures, on the Ch.C on the latter trace, this was taken by probe at the terminal 50 wire adjacent to the starter motor itself, not at the control pin on the relay. As it happens, I'm in the process of making a relay extension harness that will allow me to measure the voltages / currents directly under the starter control relay in the cabin. The reason I wanted to do this is that changing the relay (original one is marked 643, and appears to be the VW original) for a good, but secondhand, Siemens branded 40A relay, did seem to make a slight difference to the oscillations on starter current as the solenoid clicks in. I couldn't be too sure whether it was just by chance that this was the case, so I did an A-B-A test, and convinced myself that the replacement Siemens relay appeared to control the solenoid a little better.

As I don't presently have a new relay to try (it is more difficult to get quality relays with diode protection, than cheap&nasty relays from dubious sources), I am awaiting a new batch. The VW one that I ordered was the wrong type - a more typical 5-pin unit rather than a convention 4-pin unit as-fiited to this car.

I'll post some results when I have them. I am sure that you are all correct that I'm oier-analysing this a bit, however I have a chance with this car to do some experimentation at my leisure, and I do want to ensure that the customer in this case is not going to have further issues in the future.
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Re: Starter solenoid noise, VW Golf Mk.6

Postby AWright » Tue Mar 17, 2015 10:16 am

Valhalla, I dont believe the starter relay is your problem, the interference in channels A,C, and D are surely orignating from the high switching currents seen on channel B. This point is proved from the fact that, at one stage over 16 volts is seen on channel C.

To rule out a solenoid problem, try scoping the current and voltage at terminal 50, starter motor current and voltage at the switched side of the solenoid. If this test passes then, I would safely say it is a brush/communtator problem. Also remember that the current path of the pull in winding is through the brushes/communtator.

Alex

Capture1.JPG
Starter Motor Interference
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Wed Mar 18, 2015 12:20 am

Alex,
Many thanks for your responses, which are much appreciated. I hope to collate some new information, using some of the tests that you mentioned, as well as the measures directly off the back of the relay at the passenger compartment. Your comment regarding the pull-in current path of the solenoid has confirmed my thoughts that I'm certainly over-attributing too much of the noise to the relay.

The only reason I have not condemned the starter motor at this stage, and it's chances are slimming now, is that the customer who owns this car has previously reported the same symptoms on the original motor fitted to this engine (swapped-out approximately 12months ago) and that included an audible "grating" sound (to both himself and his wife) when the engine failed to start. Hence I have been keen not to jump to the same conclusion again, but appreciate that another "duff" starter motor is not beyond reason!
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Re: Starter solenoid noise, VW Golf Mk.6

Postby Valhalla » Wed Apr 01, 2015 9:46 pm

A quick follow-up to this;
I did a number of A-B-C-B-A tests with three starter relays (original VW, secondhand Siemens 40A, new Tyco 40A) which had a curious pattern of this spiking that occurs at solenoid pull-in. To be frank, it did not matter which relay was fitted, they all do this to some extent, and therefore that was ruled-out as a problem. The only interesting thing was that the secondhand Siemens relay was consistently the best of the three, wherever it was lined up in the testing order.

The car is behaving impecably on a new (larger) battery, which seems to mask whatever other issues this car might have. I have now a better theory of the root casue of this problem, which has only come about outside of any measurements made on the car. The fuel prime sequence is not reliable (initially) after the car has stood for three or more days. The fuel pump works cold/warm/hot, but the action to prime the engine fuel rail on door-open and/or ignition key cycle to position II is not immediate after long-term standing.This can only be seen after several days, and the Magnetti control system appears to have no direct measure of the rail pressure itself (hence no codes set). The car is with the customer, starting reliably each time, but they are noting any times that the pump cannot be heard as the driver's door is opened, for future diagnosis.
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