B4 tdi clocks

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noonie
still on the production line
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Joined: Sun Sep 12, 2010 10:08 pm
Passat model: B5.5
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B4 tdi clocks

Post by noonie » Thu Oct 19, 2017 4:40 pm

My clocks on my 95 tdi are playing up,speedo and lights work,but every thing else doesn’t ie fuel,temp and rev counter,I used to be able to just tap the top of the dash and it would all come back to life,now it doesn’t any ideas anyone?thanks
T4 camper,polo G40 squareback,mk1 caddy pickup

maclee
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Passat model: B3

Re: B4 tdi clocks

Post by maclee » Fri Oct 20, 2017 1:41 am

Almost certainly a dry joint, (poor or fractured solder joint), on the printed circuit board (PCB) in the instrument cluster. The physical shock caused when you tapped the area was probably enough to re-make a broken connection.. this is a classic symptom of a dry joint.

The fact that all instruments except the speedo have failed suggests you have a mechanical speedo as opposed to an electronic version.

The loss of all instruments suggest a failure of the 10v regulated supply that each of them (apart form the mechanical speedo), use.

I cannot be specific about where the dry joint(s) may lie, you will have to inspect the PCB carefully, BUT I suggest you first look around the area of the 10v regulator, which is a three legged device, probably in one corner of the PCB.

The attached photos may assist you, (I think they are of a B3 cluster so there may be detail differences with your car).
2014-03-29093951_zpsfed82507.jpg
4e1e512s-960.jpg
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noonie
still on the production line
Posts: 18
Joined: Sun Sep 12, 2010 10:08 pm
Passat model: B5.5
Location: Rugby Warwickshire

Re: B4 tdi clocks

Post by noonie » Mon Oct 23, 2017 12:22 pm

Thanks for the reply,very usefull:)
T4 camper,polo G40 squareback,mk1 caddy pickup

stuarttaylor37
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Re: B4 tdi clocks

Post by stuarttaylor37 » Wed Nov 01, 2017 11:20 pm

Do you know of a source of the regulators?

maclee
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Re: B4 tdi clocks

Post by maclee » Thu Nov 02, 2017 4:07 am

The original VW part number was:

357919803

but I believe it is now obsolete.

The component itself was a generic regulator, type number TCA700Y, which is also obsolete.

That said there is one here, from Germany at a not-too-high price of €15.80 delivered:

https://www.ebay.co.uk/itm/TCA700Y-Volt ... 0033.m2042

Google translation of the text:

Tachograph problems often cause the TCA700Y faulty voltage regulator.
Noticeable is the temporary or total failure of the displays (tank, water temperature, speed, etc., ...)

In older vehicles, the alternator, or low battery, may have a higher on-board voltage or voltage spikes. This effect causes the voltage regulator to be destroyed.


Here you get the original part.
Exchange 1: 1 without changes on the tacho board.
Exchange without soldering, just change, done.


Scope of delivery: 1 x original vehicle voltage regulator TCA700Y

Note: We only supply new components. Electronic components are excluded from exchange and return!


This will be the easiest way of replacing the item. If it is not available for any reason, you can use a different type of regulator, which is also cheaper, but its pins are reversed so the device has to be mounted up side down for the pins to be in the right place, which is possible, but as I do not know how confident you would feel about doing that I have not gone down that route.

The TCA700Y listed will be a straightforward plug-in, (no soldering needed). From memory I think you have to remove a screw that holds its tab in place, but, apart from removing the cluster, that is about it.

One final note of caution. Be VERY gentle with the circuit print that is on the back of the instrument cluster if it is blue and flexible. The plastic from which it is made was never very good quality and with age it may become brittle, so treat it with very great care and stress it as little as possible when changing the regulator.

If, on the other hand it is a rigid circuit board, as in the other photos, it will be far less delicate.

Hope that helps a bit.

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