Fitting an Alternator


I have recently purchased a 1991 Sportrak ELXi. Only 45,000 miles on the clock. On my first long drive in the dark the battery gave out and went flat. I replaced the batrery with an approved Halfords one. Next drive in the dark it went flat. I suspect the alternator........ I have a used one from a breakers to fit. Are there any things I should look outfor? Is it an easy fit?
Scratch one-s head


I'm not a mechanic, but I have changed my fair share of alternators:
Disconnect the battery negative,
Then disconnect the various wires making sure that you mark them clearly, I don't know if the alternator you have has different sized lugs for the wires,
Loosen the mounting bolts and drop the belt off and then remove the bolt actualy holding the alternator on and then Bob's your uncle, well nearly,
Put the replacement one in the same spot and put together the belt the tensioner and don't have the tension too hard but quite hard, (in the reverse procedure to removal), make sure that the wires are right and tight , don't overtighten, right!
Put the negative on the battery and now Bob's your uncle if your battery is in good nick.
Start the car.
You could measure that the current is okay across the battery terminals when the car is running; if it is at about 14 volt then it is okay. Use a multimeter.
Now having said all that, it would be wise to check that the heavy red lead from the battery is not corroded and that it is whole all the way down. Then chéck that the negative lead is whole. This should be checked because, often, problems with the electrics are because of bad earthing and power cables.
It might be a good idea to learn how to measure current and such things and, thus, save a lot of mucking about and costs at the hands of auto-electricians.
Anyway, that's my two cents worth.



Thanks for the info. I am able to use a multimeter and will measure the output current from the replacement alternator as suggested. Smile

Cables and connections.

Gary ... check the existing cable connections, check for broken cables, before you buy a replacement. Could be just a connection problem.
Make certain any alternator replacement is of same rating or a bit higher.


Thanks all for the comments. The cables and connections look in good condition, they are all well insulated and still covered in protective sleeving. I think I will swap the alternator anyway I need to bond with my car man to machine. At first glance the unit looks difficult to get to....:help:
Can anybody advise the best way to get to it and swap it with the least hassle?
Once changed are there any tests I can do with a trusty multimeter, ie measure the current into the battery at different revs, and under different loads etc.
I am fairly mechanically minded I used to work on my cars in my younger days (Ford Escorts, Capris and a Morris Ital):blush:
Any further help gladly received.


Looked at my suspect alternator problem today.
Found alternator drive belt a little loose, tightened the tension and jump started (Cos battery was as flat as a pancake). The Battery voltage climbed slowly to around 13.5 volts on idle but drops slowly to around 12.2 volts if I turn on the headlights to dipped beam. Also if you increase the revs the voltage also drops from 13.5 volts on idle to around 12volts. Went out for a short drive to see if that made a difference, but voltages stayed the same.
Am I looking for a problem thats not there? Help

Its the regulator box

The regulator box is very crude on these beasties. If the battery volts is low the box gives full field excitation for max current but as the battery volts rises a coil pulls in a pair of contacts to add resistance into the field circuit and cut the charging current.

The resistance is in at all times by the sound of it, so there won't be enough charging current when the headlights load the electrical circuit.

normal charging volts should be about 14 to 14.2 V, maybe a little less with the lights on, but still above 13.5V


if you take the car to a auto electrical shop, they will check over the system and tell you exactly what is wrong!
you could spend hours changing the alternator, and its the voltage reg thats buggered, or you could put on the alternator from the scrappy and the brushes are gone in that!
i would suspect all that is wrong is the brushes are gone in the existing alternator, i had this done the other day and it cost 30 quid.
so are you going to spend couple of hours in the cold changing a alternator that might only have a minor fault, for one you dont know works anyway? and then it might be the voltage reg. or spend a few quid to get is sorted properly!
i know what i would do!!

anyone wana ride in my hovercraft!