Alternator woes - The saga continues - SOLVED

[Flynndog]

Hi guys,

Today I did some fault finding on my rear 12V setup. I had removed the air compressor and serviced it and I had an issue where the fridge wouldn't work in the rear tub.

There are some strange anomalies there, which really lends itself to another post, but I eventually determined that my alternator is only putting out 11.96V

The alternator was upgraded last July (if some remember I blew the 80A fuse) so it's a new 90A OEX alternator.

I followed the schematics of the manual and found the 10A fuse was blown but that didn't fix the issue.

Initial thoughts? Is she dead? Would my winching last week have caused it? Or has it been there a while keeping the battery at 11.96V, enough to start the car but not charge my aux. I know it's hard with only my limited fault diagnosis so far but your advice/opinions are welcome.

Cheers

Flynny

 

[robmacca]

Does it stay at that voltage even after the engine is up to operating temp?

I know mine stays around 12.8v for a little while then kicks in and goes up to 14.4. I got a feeling this is battery related though.....(age)

I know a lot of Alternators in cars today have a Temp component to them that can limit the charging voltage until operating temp is reached.

 

[bods]

Is your battery controller working properly? What voltage are you getting at the main battery?

 

[Old.Tony]

Something doesn't sound right, and before jumping to any conclusions about what might be, I think the best thing to do is to disconnect the auxiliary system from where it connects to the main battery, then check to see if the basic alternator/battery is functioning properly.

There are a couple of things to do at this point:

1) Ensure that your starter battery is in good condition. If your starter is in poor condition, the alternator will struggle at best. To do this, either change it for a good battery (best option) or give it a "recondition charge" with a C-Tek charger or similar, then verify that an hour after the charger has been disconnected, the starter battery is still maintaining 12.8V or better.

2) Ensure that the alternator is charging properly. With a good starter battery, you should be seeing 12.7-12.8V before starting, mid-13s shortly after and within a minute or so it should reach somewhere between 14.1 and 14.7V (engine running, of course). If you don't see that (and your starter is holding 12.6V or better) your alternator is likely to have a problem.

After you've established that the base system is okay, then you can start looking at the auxiliary system.

Reconnect the aux cable to the starter battery and disconnect the cable at the auxiliary battery, keep the car turned off. Measure the voltage at the starter battery terminals then measure the voltage at the other end of the cable. This won't work if you have a VSR (voltage sensitive relay) or an isolator (which will switch off below 13.2V). If you have either, start the car, let the voltage on the starter stabilise and THEN measure both ends. This will determine the voltage drop.

If the drop is too great, your auxiliary battery won't charge properly and will have a greatly reduced capacity. Let's talk typical lead-acid batteries for a moment. If it's getting the full voltage of the alternator, it will typically charge to 75% of its capacity, and since you shouldn't discharge it to below 50%, you're really only working with 25% of its rated capacity. Further, at those reduced levels, when the fridge compressor starts to draw power, the voltage level of the battery drops and probably falls below the fridge's tolerance level (and particularly if there are long, thin cables from the battery to the fridge).

Now if you've got a significant drop on the end of that cable, the aux battery may never even reach 75% of its capacity and makes it difficult to use reliably at all. Heavy cables help greatly, as do DC-DC chargers in place of isolators, VSRs or simple relays.

Anyway, there's a bit to look at there to start with. Be interested to see the voltage figures off your starter without the aux connected.

 

[Flynndog]

is your battery controller working properly? What voltage are you getting at the main battery?

11.98

 

[Flynndog]

Something doesn't sound right, and before jumping to any conclusions about what might be, I think the best thing to do is to disconnect the auxiliary system from where it connects to the main battery, then check to see if the basic alternator/battery is functioning properly.

There are a couple of things to do at this point:

1) Ensure that your starter battery is in good condition. If your starter is in poor condition, the alternator will struggle at best. To do this, either change it for a good battery (best option) or give it a "recondition charge" with a C-Tek charger or similar, then verify that an hour after the charger has been disconnected, the starter battery is still maintaining 12.8V or better.

2) Ensure that the alternator is charging properly. With a good starter battery, you should be seeing 12.7-12.8V before starting, mid-13s shortly after and within a minute or so it should reach somewhere between 14.1 and 14.7V (engine running, of course). If you don't see that (and your starter is holding 12.6V or better) your alternator is likely to have a problem.

After you've established that the base system is okay, then you can start looking at the auxiliary system.

Reconnect the aux cable to the starter battery and disconnect the cable at the auxiliary battery, keep the car turned off. Measure the voltage at the starter battery terminals then measure the voltage at the other end of the cable. This won't work if you have a VSR (voltage sensitive relay) or an isolator (which will switch off below 13.2V). If you have either, start the car, let the voltage on the starter stabilise and THEN measure both ends. This will determine the voltage drop.

If the drop is too great, your auxiliary battery won't charge properly and will have a greatly reduced capacity. Let's talk typical lead-acid batteries for a moment. If it's getting the fill voltage of the alternator, it will typically charge to 75% of its capacity, and since you shouldn't discharge it to below 50%, you're really only working with 25% of its rated capacity. Further, at those reduced levels, when the fridge compressor starts to draw power, the voltage level of the battery drops and probably falls below the fridge's tolerance level (and particularly if there are long, thin cables from the battery to the fridge).

Anyway, there's a bit to look at there to start with. Be interested to see the voltage figures off your starter without the aux connected.

Thanks Tony,

I will discon the aux later and let you know.

At the last measure the aux was sitting higher than the starter, 12.8V. The starter (Optima Red top is as above, 11.98)

 

[Old.Tony]

11.98 is too low. Your alternator should be able to bring the battery up to around 12.7V-12.8V measured a couple of hours after turning the car off. Hard to say if that's sulphation shorting the cells, or just the alternator not doing its job - until you run those tests.

 

[Flynndog]

Tony,

Disconnected the aux (12.67V) and the starter was sitting at 12.44V.

After starting the vehicle, 11.89V while the car continued to run for about 5 minutes, no movement on that voltage at all. Once the vehicle stopped it went back up to 12.22V but was slowly settling at an increasing rate.

I wonder if I damaged the battery last week winching?

 

[Old.Tony]

Something's been damaged, that's for certain. Not sure that it's the battery - it sounds from those figures like the battery voltage DROPS when the alternator is supposed to be charging it and goes back up with the alternator stops.

Try these measurements:

1) Engine off, ignition off, main battery V =

2) Engine off, ignition on ACC ONLY, main battery V =

3) Engine off, ignition ON (instruments active), main battery V =

4) Engine started, main battery V =

That will tell us if there's something drawing power unexpectedly.

 

[Flynndog]

Something's been damaged, that's for certain. Not sure that it's the battery - it sounds from those figures like the battery voltage DROPS when the alternator is supposed to be charging it and goes back up with the alternator stops.

Try these measurements:

1) Engine off, ignition off, main battery V =

2) Engine off, ignition on ACC ONLY, main battery V =

3) Engine off, ignition ON (instruments active), main battery V =

4) Engine started, main battery V =

That will tell us if there's something drawing power unexpectedly.

Roger, will do tomorrow. Thanks for the help Tony, much appreciated.

Flynny

 

[mitch92]

Certainly sounds fishy. It almost sounds as though the alternator is pulling down the voltage, acting like a motor rather than a alternator.

 

[Flynndog]

1) Engine off, ignition off, main battery V = 12.18

2) Engine off, ignition on ACC ONLY, main battery V = 12.18

3) Engine off, ignition ON (instruments active), main battery V = 11.86

4) Engine started, main battery V = 11.86

 

[robmacca]

1) Engine off, ignition off, main battery V = 12.18

2) Engine off, ignition on ACC ONLY, main battery V = 12.18

3) Engine off, ignition ON (instruments active), main battery V = 11.86

4) Engine started, main battery V = 11.86

With those figures, I'd be swapping your Aux Battery into the Main battery position and trying the test out again. If u get the same results, then at least u know it's not the battery itself.... providing your Aux battery is in GOOD condition.

Don't suppose u have access to a spare Alternator by any chance ??

 

[mitch92]

Can you measure dc amps?? I'd be curious to see what current is flowing at engine off ignition on stage

 

[Bryce]

Id be interested to know what the voltage is at 2500rpm.
Mine wont excite itself and start charging untill 2200. But I have got regulator issues at the moment and only charging to 12.8v

 

[Old.Tony]

I suspect an alternator not pulling its weight and a suspect starter battery. Sure some electrics come on with ignition-on but they shouldn't be enough to lower the voltage that badly. First things first.

Try measuring the voltage at a higher RPM. You should have a small amount of charge at idle, but give it some beans (no more than 3000rpm) and see what it does. If there's nothing, then the alternator is NOT working like it should so we need to pay attention to that.

There are several possibilities. A slipping belt will do it. A faulty pulley (the belt turns the pulley but the pulley doesn't turn the shaft) will do it. A damaged alternator, worn brushes in the alternator, damaged regulator, unplugged cables, damaged cables, corroded cables or connections, blown fuse ...

 

[Flynndog]

With those figures, I'd be swapping your Aux Battery into the Main battery position and trying the test out again. If u get the same results, then at least u know it's not the battery itself.... providing your Aux battery is in GOOD condition.

Don't suppose u have access to a spare Alternator by any chance ??

Funnily enough I just took my old one off GumTree before it sold So yes.

I have a suspicion it may all be related to the aircon blowing the 10A fuse and charge light that has been intermittent for a while now. They share the same loom harness (ref manual EL-215) so it is something I am keeping in mind.

But basics first.

So I took the Optima out and charged it. Put it back into the vehicle and started it (ACC = ~11.9 and vehicle running was the same).

I couldn't measure current as the mulitmeter has 10A limit and would likely blow the fuse.

When I ran the engine up to 2000rpm, the volts came on at 13.9V.

When I went back to idle they stayed. So I stopped it and restarted it. Again the voltage was only ~12V and when I throttled up it went back to 13.9V. I then measured the alternator O/P and it was at 14.4V.

So I stopped it for 5 minutes, restarted it and took the following voltages

Prior to start = 12.7V
On/Instruments = 12.1V
Start/running 12.4V
Alternator = 12V
----------------------Hit accelerator up to 1000rpm---------------
Alternator 13.9V-->to 14.3V
Battery 13.9V


Now I remember it should be ~14V whenever the engine is running, can someone verify this is correct?

So I think it is fair to say we are looking around the alternator/charging circuit?

 

[Scottyspud]

Is the air con and alt dash light on the same fuse?, those new figures sound spot on, now to reconnect the aux and see if it charges now, it is sounding like a dead cel in the main batt

 

[Scottyspud]

14.4 ish should be the max you should see ( the voltage will increase with eng speed) you will see lower voltage at idle ( should be aprox 12.8- 13.5

 

[Flynndog]

Is the air con and alt dash light on the same fuse?, those new figures sound spot on, now to reconnect the aux and see if it charges now, it is sounding like a dead cel in the main batt

The alternator fuse (10A) is housed in the fusible link under the bonnet, the aircon fuse that keeps blowing is a 10A under the dash. That 10A fuse runs off to the Thermo Control Amp and aircon relay.

The alternator fuse runs directly to the alternator, but was blown. Since replaced and it made no difference that was measured anyway.

All electrical cabling for both aircon and alternator run in the same harness back to the fuse links and relays, hence why I suspect that could be the issue. It may not. Hopefully it may just be a faulty relay or Thermo Amp.

Testing the aux battery now out of the car, running the Engel fine.