Alternator charging and expected dial reading

[3Dee]

Probably nothing, but aboot 9 months ago, had to replace my yellow-top (after 3 years) as it was not holding charge. I replaced it with a red top which was great until the last month or so..

When starting, the cranking was strong from first turnover. Now I am noticing that unless I keep the thing on trickle charge I notice that on first turn, it hesitates (like trying to overcome compression), then spins freely and starts. If I top it up with the charger it does not do that.

I have taken the car out a few times for a run of about 20 miles, and after stopping and restarting the same hesitation happens. The charge registering on the dial before starting is always around 13.25 volts, and when the engine is running goes up to about 13.5 to 13.6 volts, never higher, especially with aircon on.

I am obviously concerned about the trip to Le Mans I will be making on the 2nd July, hoping that I don't find a problem starting a week later to come home.

Am I being paranoid, or do I need to investigate further.....Any thoughts would be very much appreciated!

[3Dee]

Well, when fully charged via the trickle, it does not 'hesitate' at all. but within 15 mins off the trickle, and after a couple of starts it will do this 'hesitate' thing.

I am considering the battery check thing, but I just wanted to be sure the alternator was delivering what is expected, thus the reading I mentioned before. No point complaining to the supplier, if I haven't confirmed that first...

So, what is a healthy reading with:

Ign on
Engine at idle
On a run of say 40mph

????

[3Dee]

Well, did some more tests today. Bearing in mind it is warm weather the aircon has been used a lot, and I think I may be seeing the alternator struggling.

In the cooler months it was not noticed cos the rad fan (uprated) and ircon was not frequently on together, but now they are...

Without rad fan and aircon on, then the voltmeter is showing about 14volts charge, but once both aircon and rad kick in then it drops to about 13.25. No aircon, back up to 13.8 with rad fan on.

The other thing which is puzzling me is that the alternator is putting out constant charge from idle up, with no change as you up the rev range. Is this normal?

Th unit is a Bosch. but unlike the original (Valeo TG15CO52) that came with the engine and failed, the Bosch is rated a 100A rather than the 145A that the original was and has a smaller pulley, however revs make no difference at all. I was assured by the supplier the Bosch replacment would be OK... not so sure now, cos it's not keeping up under heavy load.

Finally, charge is achieved by linking the orange wire (turn-on signal) wiring a 1kohm resistor between that and the + charge terminal, something I have never been happy with really, as it is always ON.

So, I am desperate to resolve this with little time before the 2nd July trip, so any ideas or suggestions will be gratefully received.

One mate has already suggested that I link the signal wire direct to the fuse box + area, so may be I try that?

[3Dee]

So then Steve, where do I get a new alternator (or replacement) with enough UMPH, and also one which will fit the LS7. I am already having nightmares regarding trying to replace with the engine in situ!!! That is going to be some challenge flat on my back pressing my nose against the underside! sssspecially with by B$ggered knee!

[3Dee]

Max_Torque said:

3Dee said:

Without rad fan and aircon on, then the voltmeter is showing about 14volts charge, but once both aircon and rad kick in then it drops to about 13.25. No aircon, back up to 13.8 with rad fan on.

Sounds ok to me. Remember, you will always get a voltage drop in the wiring as the alternator output current increases. If possible, measure the alternator voltage directly on the back of the alternator, and again at the battery, and maybe at the spur for the highest current consumer from the fuse box etc.

If the voltage at the back of the alternator doesn't change much when all the loads are on, then it's fine!

Coming back round though, if you remember the reason for the discussion was that I am experiencing starting issues in that the battery is struggling to turn over the engine after a run.. with the more than remote possibility of being stranded somewhere if I STOP. The battery is the second Odysses, first yellow one one failed after 3 years, and this red one is 12 months old, and only now starting to show problems. When fully charged, there are no problems, but given a run with everything on, and frequent stopping and starting, you begin to notice the issue...

Since it was the second battery, I explore the possibility of an alternator issues ie not keeping the battery charged enough....i.e., yes it is charging, but is the alternator man enough to cope with the drain... or is there someting I need to do to make it so...

So I am somwhat confused...

[3Dee]

ROWDYRENAULT said:

...... no reference no worky

Was that emfasized wiv a Nerthan accent then Lee?

[3Dee]

OK Update!

With the help of Mark, it was established that the size of wire going twixt Alternator and starter motor was not heavy enough. I obtained some 4 gauge which is like small starter motor stuff and fitted last night.
After starting:

On Idle – 14.5
With Aircon – 14
With fans – 13.8

But kept stalling – because alternator and aircon drag on engine.Can sort this out later with a dialled in higher idle.

BUT when I put main beams on after all above and with a bit more revs….Oh dear… voltage plummeted to around 13.2 and the alternator (I presume) started singing! …BLESS!
Soon as I switched off lights, the singing stopped.
May be the belt complaining.

Anyhow…that will get me through the trip, and maybe I can look again when I am back…

So a public thanks to Mark and all you guys that took the trouble to give me some tips to try...

Roll on LM Classics!

[3Dee]

Yes - I think it may well be struggling at full blat, so down the line I will be looking to have my other one (145A) tested somewhere and repaired if necessary.