TinyTim

Things aren't going well! The Bosch alternator is a dud. One of the slip rings is knackered. My friend has checked out the origial Valeo 110A (VW AG 03F 903 023 E or Valeo TG11C086) and he reckons the diodes are all good, as are the slip rings and brushes, so it must be the regulator. The regulator/brush packs for these seem to start at about £52 on Ebay, whereas similar looking ones can be as little as £25. New alternators locally are from £145 and not much better on Ebay. Any suggestions? Is the Bosch 140A of any value, needing new slip rings and maybe a regulator brush pack? Only cost me £30 via Marketplace. Seemed nice folks!

There are definitely no other serial numbers on it. That is indeed the regulator part number.

The Bosch 140A is as follows: BR14 -C-L F and then OOM 144 197. I connected it up on the floor under the car, with a suitable earth, and the battery warning light on the dash did not illuminate. I then tried the same with the Valeo and the warning light did illuminate. This did not please me. Tomorrow, I shall take both alternators to a friend who is gifted in the field of electronics and he will discover what is going on with them and possibly get both of them working. He told me the other day that he has even been repairing LED light bulbs! I don't suppose there is much wrong with either of them.

Thanks for the confirmation of the blue wire/pin1. I hope that when I refit the thing it will now work! The biggest problem I find with removing and fitting is the tightness of the lugs to get it in position before the bolts go in. Thanks for your advice and persistence. I hope I have saved you some aggro.

I took the alternator (Bosch 140A) off again to see why the plug wouldn't go in. The reason is pictured below. It fits round the connector within the plug and has one groove on one side and two on the other. The grooves were obviously right for the Valeo alternator, but not for the Bosch. With it removed the plug goes in properly. In the Bosch alternator socket the pins are numbered 1 and 2. The blue wire goes to 1 when the plug is in. If that is correct, then the problem is solved. The shape of the plug being what it is, it's hard to see the purpose of the pink insert.

I've checked continuity from the alternator output terminal to the battery, which is fine. I contacted an auto electrician, hoping to get both alternators bench-tested, only to be told that they are 'smart-charging' and can only be tested when installed in the car! I've been too busy today, but tomorrow I'll remove the 140A Bosch and investigate the problem with the plug.

I've measured for volts on both wires on the plug. I got slightly less than battery voltage on one wire and a bit less again on the other. My voltmeter battery is weak, so I'm going to pick up a new one. I'm not convinced the plug is giving a contact. It just doesn't seem to go in far enough and there is no friction at all when it is pulled out. I wonder if there is something in the socket stopping it. Tomorrow I'll take it off again and investigate. i'm retired and have 3 other working cars, so I'm not giving it my undivided attention!

I will do that. Thanks.

Now it's installed I can't see much at all. It was previously on a Seat Ibiza 1.2 TSI, I believe.

Oh dear, I've probably got two duff alternators now! I understand that the usual problem is the brush/regulator pack. I'm thinking of removing the Bosch 140A and taking it and the Valeo 110A to an auto-electrician for testing. At least I'll know then.

Thanks for the detail regarding the 2nd wire. I'll be returning to the problem tomorrow and will check for voltage on the blue wire with the ignition on. Going offline now, but will look later.

I've tried revving the engine, but still no output. I presume once the output is there it is still there when the engine is back at tickover? It wouldn't rev past 3500. Is that normal?

Thanks Breezy_Pete, I'll try the revs. If the blue wire is the exciter, what's the other wire in the plug?

Here's the history: My battery went flat and would not restart the car after parking. Restarted from jumper pack. Driven home 50 miles. No restart. Spare battery substituted. Started fine, used intermittently for 2 or 3 weeks, battery weakening. Replaced Valeo 110A alt. with a used and reputedly tested Bosch 140A alt. Exciter plug didn't click home positively. Re-charged original battery refitted, started fine but not charging. . Battery light does not appear on display when ignition turned on and never appeared on display when engine running during the time I've been having issues. An experienced mechanic friend says that the warning light should come on before the engine is started (as I would expect). He suggested that if the bulb had failed, it would affect the alternator, i.e. no charge. I wonder if the light isn't coming on because the plug isn't giving a good contact and maybe that's why it isn't charging now, but wouldn't explain the original fault, as the plug fitted the old alternator fine. My questions are: Why would the plug not click home in the Bosch alternator? Can warning light bulb failure affect charging? If the plug isn't making a good circuit, would that stop the warning light working?