Outer Limits 4x4 Board

I am just wondering how to test the alternator in my GQ ?

I also need to test the pump on the back of it.

The sparky said the alternator wasnt charging properly but I fixed the brake lights and some dash lights and now it battery light isnt coming on.

I just dont want to spend $330 if I dont have to.

Cheers Nick

Well for starters, get a multimeter and check the voltage at the battery with the engine off. Then start the car, let it idle for a minute or so, give it a stab as well, and see what the voltage does. It should go from 12.1-ish with the engine off, up to over 13V with the engine idling.

If that checks out, then turn on the headlights, whatever else you've got that uses electricity, and watch the voltage. If it still holds up then, basically, your alt is doing its job.

If it fails this test, it still doesn't mean it's stuffed, it's just a basic first test. If it passes though, then it is working.

If there's a problem I still don't see why it would cost $330, a new set of brushes is $20 tops, and a new regulator about the same. Bearings cheaper. I think people often replace alternators that have very little wrong with them.

As for the vacuum pump, I would have thought that the test would be whether it sucks or not

chimpboy wrote:As for the vacuum pump, I would have thought that the test would be whether it sucks or not

Yeah that makes sense, Just wasn't sure if you needed to check certain pressure etc.

I checked like you said an it all checks out but it seems to come back up to 13V slowly. About 0.01 of a volt a second. Is this a problem or is that standard ?

Cheers Nick

For the vacuum pump you'd probably know if it wasn't working as the brakes wouldn't stop the car.

Also, is 13V enough? I'm not sure what other alternators put out, but the Disco2 alternator varies between 14.2V and 13.5V typically, with idle at 13.7/8volts. My old alternator used to start at 13.7V and drop to 13.2V and it gave all sorts of funny problems, especially with the dual battery isolator and the level of charge in the batteries.

My alt is dead and I have the same voltage at the battery as Alt. it should be 13.8v when running and you may need to rev it.

Dependig on your model it could also be the voltage regulator. But if your getting a higher voltage then when the car is turned off, I'd say its fine, what was happening to make you think it was dead
???????????

The alternator light comes on sometimes when you start it and flashes and flickers for about half a minute and then gos out.

I sparky reakon it wasnt charging but I dont even think he tested it, Just started the car and said its not charging properly.

Nick

it should jump upto 13.5v or above very quickly, they should charge at 14-14.5volts with a few revs and hold no less then 13.5 with the headlights on. if the charge light flickers on ocasionly, it probly out of brushes. when they run low on brushes they will charge somtimes, so when the elecy checked it, it may not have been chargeing. they do add up in quite a hurry when it comes to repairing them, a set of brushes will set you back about $20, plus around $80 fittting. but most of the time when you open them up it has noisy bearing at $9-$60 each depending on the bearings, then most of the time the brushes are too time consuming to replace, and the regulators are old and unreliable so that gets replaced at $25-$200 depending on the make. then you have the oil seal at around $15, and if its been leaking oil into the alternator, which is the major cause of alternator failure, the slip ring will be worn out at $20-$80 to replace. then you need to add around 1-1.5 hours labour if it off the vehicle or in some cases you can double those times if they remove it at between $77 per hour (which is what we charge out at) to ive heard most work shop in the capital city are charging out at over $100 per hour. so when you add it up your better with the new $450 unit that comes with a new vac pump and a warranty. you may find someone who will just fix the imediate problem, but now days most workshops who have done people a favor and done it on the cheap, have had there ass bitten when in 6mths after replacing brushes the bearing siezes 100km from no where and they have the customer on the phone abusing them and expeting them to pay for the tow truck home.

Oooh yeah. I spat an alternator bearing at Marree a few weeks ago. Not nice, but the pub was a good spot to spend a few days while waiting for the parts. I guess the message is to do it properly.