Alternator failed - how to safely continue driving

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dag019

dag019

Well-Known Member
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Location
Warwick
My alternator seems to have failed. My rev counter is no longer retreating the dash battery warning light is permanently lit.

However my volt metre (just the standard Land Rover so not an irate) show increased voltage when the engine is running.

Engine off:

IMG_2089.jpeg


Engine running:

IMG_2087.jpeg


With the engine running it looks to be sitting a little higher than normal. But is showing increased voltage. Would this be charging the battery, over charging the battery, doing nothing?

I need to drive about 80mile each way tonight for work. I can leave early enough so that I only needs headlight for the return trip. I have led lights (other than indicators and on a quick google that looks likely to be around a 10amp draw. I have a 110amh battery so I make that 11hour of running? Obviously my battery is not new and I need to start the vehicle but from this I am thinking a three hour return trip with only half requiring headlight should be ok? Do people agree?

Second question should I disconnect the alternator complete based on the above voltmeter readings as it may be overcharging?
 
Those two pictures of the gauge show it is charging. What is the alternator rated to? 60-80A is common I think, and that is at max revs. It probably pushes 40A or less normally (I don’t think it will fail and over-charge, just undercharge). I think an 80 mile drive will be fine, and will tell you if the return trip is okay to try. Take an extra battery with you perhaps?
 
To check. Use a multimeter set in dc volts across battery terminals will tell if alternator is still working. It may be the bit that cuts the power to the dash charge lamp has quit. Engine on [and rev it a bit] and off. See if it agrees with your dash meter.
 
A battery is considered flat at 50% charge. The engine will die probably after 10-15 mins if the battery is not charging.
You need a volt meter, as above, to see what's really going on
 
You can keep a tdi running with a 9v battery from a tv remote wired into the stop solenoid. They really are the old fashioned mechanical type that require virtually no power to run.

On this I went with the safe option to protect the battery recommended by @Hicap phill on my other thread and pulled the belt off for the journey. The journey proved alternators are clearly over rated on an old mechanical engine. I fully charged the battery, drove two hours to work with the last half hour using headlights, followed by another two hours home using headlights. Two engine starts, 2.5hours of headlights, and other general light use while driving and made the round trip with no issues.

As mentioned above I do have LED lights in everything other than indicators and a big battery, I also did not use heater, radio, wipers, so the only draw on the battery was starting and lights. Now just need the new one to arrive which was a supplier order form paddocks!
 
A couple of years ago I was driving my Ford Focus and was about 45 mins drive from home in the day when the battery warning light came on. I kept going thinking I would get back fine however after a couple more miles the electric power steering shut down [heavy like a series with a flat:D] I had switched off other items like blower and radio]
Five miles to go and engine went into limp mode and no way would it have gone up the hill to home. Modern [ish] cars have a batt warning lamp that comes on when the batt volts are already low so one will have little driving time left.

Recon this may have been your experience @kermit_rr.
Fitted the car with a digital voltage reader.
 
tottot said:
A couple of years ago I was driving my Ford Focus and was about 45 mins drive from home in the day when the battery warning light came on. I kept going thinking I would get back fine however after a couple more miles the electric power steering shut down [heavy like a series with a flat:D] I had switched off other items like blower and radio]
Five miles to go and engine went into limp mode and no way would it have gone up the hill to home. Modern [ish] cars have a batt warning lamp that comes on when the batt volts are already low so one will have little driving time left.

Recon this may have been your experience @kermit_rr.
Fitted the car with a digital voltage reader.
Click to expand...
Only ever had an alternator fail once. So far. New (to me) car, my first modern vehicle! Light came on within 5 miles of collecting the car and i broke down on a busy roundabout!!!!
 
New alternator arrived yesterday (my mistake, first one arrived Friday but realised I had ordered a defender one not a discovery one and they are handed opposite!) and was fitted today, all being well it should not require anything for a good wile now, but it was the britpart branded one rather than a proper name.

The expriance has taught me that an alternator truly is fairly optional for an old tdi even when running in the dark. I did about 500 miles in the week i didnt have one, with about 6 hours of night driving, with the battery charged when at home every couple of days.

I will post a pic when home of the alternator test sheet that came in the box. On a quick skim of the chart it looks like it is good for 160amps at 4krpm which sounds very high!
 
dag019 said:
New alternator arrived yesterday (my mistake, first one arrived Friday but realised I had ordered a defender one not a discovery one and they are handed opposite!) and was fitted today, all being well it should not require anything for a good wile now, but it was the britpart branded one rather than a proper name.

The expriance has taught me that an alternator truly is fairly optional for an old tdi even when running in the dark. I did about 500 miles in the week i didnt have one, with about 6 hours of night driving, with the battery charged when at home every couple of days.

I will post a pic when home of the alternator test sheet that came in the box. On a quick skim of the chart it looks like it is good for 160amps at 4krpm which sounds very high!
Click to expand...
you can swap the hand of the alternator by simply undoing the three or four very long screws pulling them out rotating the ends of the alternator in relation to each other refitting the screws and tightening them up
 
lynall said:
you can swap the hand of the alternator by simply undoing the three or four very long screws pulling them out rotating the ends of the alternator in relation to each other refitting the screws and tightening them up
Click to expand...
It depends on the alternator. You can do that with the Lucas alternators, but certainly not with Magneti Marelli as I tried that with the one I got form Newbury and then had to resolder all the windings before giving away as the end cover is integral to the rest of it. The new britpart one looked far more similar to the Marelli than the Lucas unfortunately.
 
IMG_2210.jpeg


The test sheet that came with my new alternator. If I am reading the performance curve correctly does that mean that at a little over 4000rpm it will produce 160amp? I will need to do some maths looking at the belt gearing but the engine can do 4k rpm. The pad pump is maybe geared down (crank pulley smaller than pas pulley) but the alternator is then geared up (pas pulley larger than alternator pulley).
 
dag019 said:
View attachment 338308

The test sheet that came with my new alternator. If I am reading the performance curve correctly does that mean that at a little over 4000rpm it will produce 160amp? I will need to do some maths looking at the belt gearing but the engine can do 4k rpm. The pad pump is maybe geared down (crank pulley smaller than pas pulley) but the alternator is then geared up (pas pulley larger than alternator pulley).
Click to expand...
I've just seen, voltage set point 13.8v
That's too low for a modern battery?
 
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