DIY Guide Request: Alternator

[rich106quiksilver]

Not sure if this is the correct section to request a DIY guide but please move if not.

I was just wondering if someone could create a guide for removing the alternator / changing the belt. I want to change the belt on mine and it's probably quite simple but knowing me I will break something! Noticed there wasnt a guide for this and it could be helpful to other members too,

cheers :)

[joe106gti]

Checking the alternator

The alternator charges the battery when the engine is running. If the alternator is not working correctly it may not charge the battery properly or in a worse case scenario, overcharge the battery and damage it.

With the engine running and idling, connect a voltmeter across the battery terminals. The reading on the voltmeter should be between 12-13 volts. Increase the engine speed slowly to ~2,500rpm and the reading should still be between 12-13 volts.

Switch on as many electrical components as possible (with the engine still running and idling). For example, radio, lights, heater, rear window heater. The reading should now be between 13-14 volts.

If the reading in any of the tests above is different, the alternator may be faulty. If the reading is under the minimum value, the alternator will not be charging the battery correctly. If the reading is above the maximum value, the alternator will be overcharging the battery which could cause damage.

It's a good idea to check all wiring as a starting pointing before ordering a new alternator, going to an auto-electrician or do anything else. It may be something very simple. Connectors can become loose or corroded.

Checking the auxiliary drivebelt

The auxiliary drive belt is the belt that runs from the alternator. This sometimes get confused with and refered to as the "fan belt" (which is incorrect). A damaged or slipping drivebelt can be the cause of battery problems.

You should check the auxiliary drivebelt for cracks, splitting, fraying, shiny patches and/or missing "teeth". If any of these faults are found, it's advised to renew the drivebelt. Note: Ideally you should remove the belt and check it. At the moment, this guide does not cover removing the belt or replacing it.

Ensure that the drivebelt is tensioned correctly. If the drivebelt is under tensioned, the belt can become damaged. If the drivebelt is over tensioned, it can damage the alternator. In the centre of the drivebelt, apply pressure with your thumb and there should be ~5.0mm of play in the drivebelt.

To adjust the drivebelt, ensure the upper bolt on the alternator is done up tight and loosen the lower bolt. There will be an adjuster bolt and can be tightened or loosen and by doing this, will move the alternator up or down (on an axis) which will either tighten the drivebelt between the pulleys or slacken it off. Adjust until the correct amount of play is achieved in the drivebelt and remember to tighten the lower bolt when finished to secure the alternator in its final position. It goes without saying but do not have the engine running when doing this!


courtesy of Dave R.
im doing mine soon in the next couple of weeks so ill make a guide when done. if stuck ill get the hanyes out and see what it says.
also, not really sure where to request one. maybe in the engine section?

[rich106quiksilver]

Cheers Joe, I have got the Haynes so will give it a good read over. Hopefully wont break anything!

[fred]

Its easy rich, just a tad hard to get to one of the bolts :)

[rich106quiksilver]

Cheers Fred gonna tackle it today hopefully!

[Quik_Pug]

Quick Question...

How can i check an alternator is working fine off the car? I have one for a 106 GTI but not sure if its working condition or not?