Alternator problem?

[garyt]

Hi ashman, thanks; yes I used a multimeter this time and got the same readings for voltage.

So, I got 0v from the body of the alternator to the battery negative.

But, embarrasing, I found a white wire (the ones from the engine) had completely come off the double relay, at the moment I can't say which one it is. Now the car starts first time fine again. I don't know how long it has been like that so I'll have to do the tests again, maybe that was the cause of the pulsing (I suspect not). I expect the wire came off when I took off or put on the air cleaner and AFM unit, which presses on the wires.

Yes, the Lidl tester is very basic and doesn't tell you much.

I have to get the camber adjusted today at the tyre shop and new front tyres. I should have done that on the last set but trying to save money is often a false economy, the tyres wore out on the inner edge. I may have cured it now but will have to get the pros to do it anyway.

If I don't use the lights the car is fine for charging as the battrery hasn't lost any charge recently, so I'm ok in the day.

I've booked it in for 'controle technique' in two weeks so its scary.

[garyt]

Now I've sorted the tyres (got some Bridgestones on the front 175/75/15 and they are very good and the alignment was the problem, now fixed).

Car is starting well, battery does not seem to be getting run down. But its when I use the lights that I think I get the problem with the charging. Still looking for bad wiring, having to check the whole lighting circuit.

[garyt]

New readings:

Battery = 12.6 v.

Alternator at B post = 12.6v.

Battery negative to Alternator body = 0v.

When Alt recharging Battery = 13.2v.

When revving also 13.2v (measured with Lidl tool)

At the Coil positive with ignition on (not started) = 12.36v. (Multimeter)

At the Coil when cranking starter = 11.27-36v.

When started at the Coil = 13.6v. Rises when revving.


So I reckon the multimeter is recording a rise in voltage when raising rpm. But maybe not enough to reach 14v ... What do you think?

[ashman40]

Not clear from the above... WHERE are you taking your voltage readings when you rev the engine?
With a fully charged battery (outputting 12.6v) and an alternator working well, you should get a reading of 13.8v AT the battery terminals. For example, if you get 13.8v at the alternator B+ but can only get 13.5v to the battery you are not properly recharging the battery.

From your descriptions it sounds like there is a good chance your alternator is in need of replacement (borderline or weak output). While 13.8v at the battery is min spec, I like to see 14.0v or more. This ensures the battery is recharged quickly and reduces the chance the battery is not fully recharged if you have to take a short drive.
_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[VW_Jimbo]

Sounds like a bad Alternator to me.
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[garyt]

Thanks chaps. Ok, is looking like the alternator. The borderline figures would explain the erratic starting. Car is starting ok at the moment though.

I took the reading for the 13.6v from the coil positive when I noticed the rise as my wife started the car (testing the load with the starter cranking).

I will test it from the battery with the multimeter.

[garyt]

I tested it at the battery while running with multimeter:

Battery before strating is 12.36v.

Went up to 13.99v on start up, but varied.

With full load (wipers, fan, lights, radio) I got fluctuating readings, but seemed to level out at not more than 13,33v.

After switching off all items it fluctuated between 12.99 - 13.33v. Not steady.

The lights are not flickering anymore.

?

[garyt]

Going up to 13.99v on cranking seems a good sign maybe?

[ashman40]

There is fluctuation in the alternator output. After all it is converting AC voltage to DC. But it is NOT something that should show up on your voltmeter when set to read VDC.

13.99v is okay if this is a steady voltage reading at the battery. But if this quickly drops off to only 13.3v I'd be concerned.

One last thing you could check... I'm assuming your alternator is an internally regulated one (most common) and there is the wire from the Gen lamp running to the D+ on the alternator. With the ignition ON and the engine NOT running, disconnect this wire from the D+ terminal and test the end of the wire for voltage. You should get very close to battery voltage. If you ground the end of this wire you should seen the Gen lamp light up brightly.
While you are there and the D+ wire is still disconnected, test the D+ terminal on the alternator for voltage. The diodes in the alternator should PREVENT voltage from the B+ wire passing thru the alternator and coming out the D+. You should get no more the 1.0v on the D+ terminal (probably less). If you get more than that, your internal diodes have failed and the alternator needs a rebuild.

In the end I think you may need to remove your alternator and take it to a shop that has the means to test it off the car. They can tell you definitely if it is operating normally.
_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[garyt]

Thanks for the advice. I'll try that test.

The alternator has the internal regulator, but it is a removable unit with the brushes, I changed this a couple of years ago and it looks ok as far as I can tell.

The wire you are talking about - I have a connection I made in that when I had to renew the wire, so I can do the test easy, but maybe that connection needs redoing, I checked it and it seems ok but I will anyway after the test.

When you say internal diodes could be bad, do you mean those in the replaceable brush/regulator cartridge (that would be too easy!)?

I can't really get it tested out of the car now, need the car to get it through a test. If its not ok I'll just have to get a new one.

Given this alternator has connections for a load of white grounds from the FI as well as the other two posts, am I looking for a specific type of alternator or will any of the usual ones fit?

Thanks again.

[garyt]

OK, it took a while, flooded garage etc.

Finally I could not start the car at a garage where I stopped for petrol, and the owner said he would diagnose it for me for free, and did, and it was the starter motor. It is a fairly new one that I put on but not Bosch, was cheap bought online after putting in all the correct details. Apparently, apart from it having a defect it was also not correct for my model. Now with the new Bosch unit it starts up fine again and has a completely different sound. They also tested the alternator and it is good.

On the way to get it fitted at the same place the accelerator cable broke, LOL. I fixed it temporarily with an electrical connector. Now I've got to look up how to replace that, the new one doesn't look like the old one...