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!

[Racing Roj]

3 Dee
How long are you leaving the car before each run?
I have had a number of cars and bikes which got infrequent use and in all cases they needed a trickle charge when not in use.
I know you haven't got much time to test this before Le Mans but that would be my first port of call.
Also as you haven't had the battery for very long can you take it back to be tested, and if not get a local tester to check it.
Enjoy Le Mans it's on my to do list among about 500 others.

[F.C.]

Mine did this, turned out to be a tired starter motor.
Turns over really quick now, even when the car has been left off charge for a couple of weeks.

[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

????

[The Italian]

Better than 13.5 , optimal is 13.8 to 14.2 volts output from alt

[anonymous-user]

You'd be better off measuring the "minimum" battery voltage during the crack event. Some multimeters have a "min hold" function for this, or if you can borrow an osciloscope / scope meter, then that makes this very easy!

(as batteries age, there capacity and internal resistance increase, and this results in a lower voltage when high current is being pulled, such as when you are cranking)

[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?

[Steve_D]

3Dee said:

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?

Yes, that is what the voltage regulator in the alternator is designed to do.

3Dee said:

The 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 replacement would be OK... not so sure now, cos it's not keeping up under heavy load.

I’ve not looked at mine to confirm the rating but it seems likely your new unit is not man enough.

3Dee said:

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.

Not quite. It only comes on with the resistor passing current when you turn the ignition on. It is then passing +12V to the alternator where it earths. When the alternator charges it puts +12V on that end of the wire so with +12V at either end of the wire nothing happens and no current flows.

3Dee said:

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

No. see above.

Steve

[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!

[anonymous-user]

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!

[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...

[The Italian]

Sounds like your alternator does not have enough electrical pressure - push/amperage.
Also sounds like your battery has to work too hard, this will eventually wear on it.
I would go back to a higher rated alternator - 100A sounds too weak with air con and fans, you will always be "catching up".

[anonymous-user]

As i said earlier, measure the cranking voltage during the "hic-uppy" starts and the non hic-uppy ones. Otherwise you'll just be changing stuff randomly!




(remember, starting "hiccups" might be caused by other factors, such as different cranking ignition angles, throttle positions, oil temps, engine temps, etc etc)

[Storer]

It maybe worth removing all your earth strap connections to the chassis, cleaning everything thoroughly, and reassemble.

Good place to start before you get the credit card out.



Paul

[mt308]

Storer said:

It maybe worth removing all your earth strap connections to the chassis, cleaning everything thoroughly, and reassemble.

Good place to start before you get the credit card out.



Paul

I was about to start a new post on electrical gremlins but this seems relevant to my issue too...

Having had my car on the road for over a year with no real issues, yesterday it ground to a halt after briefly spluttering. After much head scratching and help from a friend a loose negative terminal connection was the diagnosis. Feeling like an idiot after it was tightened it started and off I went - just a mile or so back to home.

Today I drove it about 45 minutes with no issues to the in laws. Then I took a chap out for a demo, ran really well but then twice did the same again. The first time it looked like it was dirty around the negative terminal, but now it is clean and it is still doing it intermitantly. I am wondering if it is a red herring and maybe something is getting hot elsewhere and a few mintes is enough to let it cool.

It is definitely electrical. The cooling fan and hazards are weak when the engine dies, then when I have played around a bit everything is strong again. 16v reading on the battery gauge so I think its charging fine.

Would a poor earth connection elsewhere on the loom also give same characteristics or would only certain things stop working?

I got home after 4 further failures, and some at not nice places to have to pull over (dual carriageways with no hard shoulder etc.).

Next weekend I'll strip down the battery connections and give a good clean and wire brush.

Also appears to me the wing nut arrangement on the terminals of the red top looks a little small?

Any suggestions most appreciated!

Mark

[Storer]

Check the earth strap from the engine to the chassis and all the positive main cables from alternator, starter, etc.

It may also be worth checking the ignition key/button wiring as some have had issues with the wires getting rather warm.


Paul

[ROWDYRENAULT]

I have said it before and learned it out of years of embarrassment. Anytime anything electrical goes wrong check grounds first no matter hw much you think you have it figured out. Today this is even more important than in the past because everything in your fuel injection system be it a stock G.M. or a Motec relies on a solid ground for reference. no reference no worky

[3Dee]

ROWDYRENAULT said:

...... no reference no worky

Was that emfasized wiv a Nerthan accent then Lee?

[mt308]

ROWDYRENAULT said:

I have said it before and learned it out of years of embarrassment. Anytime anything electrical goes wrong check grounds first no matter hw much you think you have it figured out. Today this is even more important than in the past because everything in your fuel injection system be it a stock G.M. or a Motec relies on a solid ground for reference. no reference no worky

I'll show up my ignorance here.....but happy to do so to learn how to make the car work!

Could it be any of the earthing points that would give the symptoms I am getting (cooling fans, lights, engine all going or getting weak rather than just one thing)?

Is there a way of protecting the grounding points from getting mucky? (e.g. covering them with something or perhaps spraying them with copper ease or similar?

Mark

[Steve_D]

The biggest mistake people make is leaving paint or powder coat under the earth connections.
Clean and reassemble with Vaseline or copper grease then follow up with a coating of same over the assembled joint.

Had a car the other day with the engine earth onto paint. As the earth was not working the start current took the only remaining route back to the battery...the throttle cable. Reminded me of the same issue common on classic minis back in the day.

Steve