300 Tdi Disco Tachometer

On or around Fri, 5 May 2006 09:00:02 +0100, "Paul - xxx" enlightened us thusly:

loose connection to the W terminal on the alternator, and/or alternator going flaky.

On a 200 TDi, it can be alternator drive belt slack, but on a 300 TDi the serpentine belt mostly either runs or doesn't.

195 quid plus vat for a replacement alternator here, the other weekend - front-end bearing had seized and collapsed, taking the casing with it. Parts supplier kindly took the surcharge off, too - I was expecting to have to pay that, 'cos I doubt there's much salvageable on the old unit.

Austin Shackles came up with the following;:

Cheers Austin. I'll have a look later, when I get a o tuit.

Hi Paul,

Mine was the W connector - took dealer here 4 efforts to fix it - they were just cleaning the conector - only got fixed when they crimped a new spade clip on.

Cheers! Graham Carter Harare Zimbabwe

On or around Fri, 5 May 2006 19:21:29 +0200, "Graham Carter" enlightened us thusly:

seen the same on a couple of 'em. Dunno why the spade connector, except perhaps that it makes it more difficult to connect the wires wrong way round. The one I've just put on the tranny has captive-nut things like the disco has on the D+ terminal, for both of them.

Austin Shackles came up with the following;:

You were both right.

The connector came off wayyyy too easily, a completely dead tach proving I had the right wire, and a quick spray of contact cleaner had it working better but still intermittently hiccuping. After a good look at the connector I decided, as you say, to make sure the spade was well attached, and in the end soldered [1] the spade to the wire. The bugger won't come loose again in a hurry ;)

Many thanks.

[1] I race electric model cars and used a very high temperature solder and iron, so it _should_ be OK.

There can be problems with a soldered joint, rather than using a properly crimped connector. I gather it's a side effect of the solder wicking up with wire, and leading the the wired being differently strained when it flexes. If you think about it, one of your models has an incredibly short operating life, compared to a car.

But I know the temptation of a hot soldering iron.

I think the damage is maybe due to flux residue rather than the solder

On or around Tue, 09 May 2006 11:34:07 GMT, "GbH" enlightened us thusly:

I thought it was that the heat alters the properties of the copper. But there is also a question of strain relief and vibration. By soldering, you generally end up with a short rigid section of wire, and the flex point moves to the end of that. On a crimped terminal, there's usually some kind of strain relief in the bit that grips the outer casing of the wire.

Austin Shackles came up with the following;:

Hence why I mentioned my hobby ... I've soldered only where the connection would be crimped, a very quick job, a very short solder section and little to no wicking, but an extremely solid joint, finished with a short length of heat-shrink wrap.

I'm happy it'll last. ;)

Putting my ex-Wireman hat on - crimped joints should *never* [1] be soldered, a crimp is a flexible joint (the the individual wires in the cable are free to move a bit), wheras soldering will make it rigid, effectively turning cabe into a single wire which will shear when bent (flexed), as in almost all automtive applications.

Richard

[1] there are exceptions, mostly heavy current applications like car battery leads and electrical supply, but only where the joint has been designed that way.

I confess to a modified trick on that.

I crimp the wire grip and quick solder it. Quick as in not melting the insulation. Hence I have a waterproof bond between the metals. Cool it, normally by 'fizzing' in on the soldering iron sponge then crimp the grip on the insulation so I still have the slight flex as a strain relief. Then silicon grease, then a rubber (not solid plastic) shroud. I've never had to go back and rework a connection I did like that and that's on boats.

I think the problem with soldering a crimp is that you destroy all the give in the insulation crimp and throw the flex onto the metal-to-metal join. Going to sea everything flexes.

nigelH

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