Air con compressor kicks out on tickover

nigelc116 · Unread post by **nigelc116** » 12 Jul 2006, 18:22

My Xant 1.9TD Est has the heater fan problem so I rewired that last weekend (thanks to this forum)

. I had to take the feed for the new relay from the Cigar Lighter after first changing the position of the fuse so that the Cigar lighter only works with the ignition on.

Today I've had the air con serviced £60 +VAT

and now freezing cold but.... the Air con compressor kicks out on tickover kicking back in above 1200 revs.

Since I rewired the Heater blower, the batterry warning light lights up once I've switched the engine on and the blower won't run while this light is on. The light doesn't go off until I've flipped the Accel pedal. I've put a metre across the battery and once the engine has started the volts are low rising to 14V once the accel pedal has been flipped.

I can't help thinking that the two problems are linked

Can anyone help?

Unread post by **Peter.N.** » 12 Jul 2006, 21:26

The ignition lamp provides the start up voltage for the alternator by energising the rotor, once it starts charging the voltage on the alternator end of the lamp rises to that of the battery voltage, so with the same voltage on both ends the light goes out. It could be that the compressor will not engage because the battery voltage is to low, but the problem is more likely to be to do with the alternator. Check and make sure that the belt is not slipping, if OK you probably have a faulty alternator.

nigelc116 · Unread post by **nigelc116** » 15 Jul 2006, 07:21

I can't recal this hapening before I re-wired the heater, could I have made a mistake doing this that could cause the charge light to remain on?

Unread post by **Peter.N.** » 15 Jul 2006, 08:17

I wouldn't have thought so. The warning lamp is normally wired directly between the battery + and the alternator, so unless you have disturbed the wiring in that region it shouldn't be affected. If the alternator does not charge at tickover but does when you increase the revs, it points to a faulty alternator regulator pack.

nigelc116 · Unread post by **nigelc116** » 16 Jul 2006, 12:11

Thanks for the advice Peter N.

I've been having a mess this weekend!!.......

The belt is tight and it's one of the auto tensioning ones so I'm confident that the belt isn't slipping.

I've cleaned up all the connections so that corrosion isn't a factor

I'm thinking about taking the alternator off and take it into an auto electrician so that hopefully they can repair it.

Is the alternator regulator pack repalceable or do I have to have a new alternator?

Unread post by **Peter.N.** » 16 Jul 2006, 16:13

Well, it is replacable and a lot cheaper than a new alternator, but whether it would be when you include labour and anything else they find wrong, I don't know. A new one from GSF is about £100.00. You could ask them for an estimate.

BonceChops · Unread post by **BonceChops** » 16 Jul 2006, 23:34

Peter.N. wrote:The ignition lamp provides the start up voltage for the alternator by energising the rotor

that does not sound right. That would mean your battery would go flat if the lamp went. One side of the lamp is fed from its own rectifier diodes on the alternator and the other side, as you say, to the battery +ve.

dnsey · Unread post by **dnsey** » 17 Jul 2006, 08:25

Have you checked the actual battery/charging voltage at tickover?

dnsey · Unread post by **dnsey** » 17 Jul 2006, 09:45

Sorry - just noticed that you've done that!
I sugget that you do the same, but measuring at the alternator itself - both +ve and earth connections. If the output is still low, check the field coil voltage. If that's OK, you definitely have an alternator or regulator problem. Bosch regulator packs are quite ceap and very easy to fit, but some of the others are a different matter

nigelc116 · Unread post by **nigelc116** » 17 Jul 2006, 12:03

How do I test the field coil voltage?

Unread post by **Peter.N.** » 17 Jul 2006, 12:15

BonceChops - Well, I dont know about all cars but it certainly did on my CX, because after I had the dashboard out the alternator wouldn't charge and I found it was because I had disturbed the ignition lamp and it wasn't making contact, directly I refitted it, the alternator came to life again!

AndersDK · Unread post by **AndersDK** » 17 Jul 2006, 12:42

nigelc116 wrote:How do I test the field coil voltage?

You dont do such things on an alternator anymore. That was back in the '70-es

Any recent alternator is tested by its charge voltage over the battery poles.

With engine running (alternator charging) the battery pole voltage should read some 14.1-14.4V.
Its important to read the battery voltage directly on the battery poles to get it correct.

If the voltage reading is lower - your alternator is not up to its job. Period.

nigelc116 · Unread post by **nigelc116** » 17 Jul 2006, 16:04

Thanks AndersDK

I've cheched the voltage across the battery and it is 12.5.

I am proceeding to remove the Alternator to take it to an Auto Electrician tomorrow to hopefully get it repaired otherwise it will be £100 for a reconed replacement.

Just off into the garage to sweat, swear and loose a bit of skin off the knuckles!!

Any tips for a swift removal?

BonceChops · Unread post by **BonceChops** » 17 Jul 2006, 18:00

Check the connections on the alternator are good. I have known partially corroded terminal lugs on alternators to give poor charging due to a high resistance connection.

dnsey · Unread post by **dnsey** » 17 Jul 2006, 18:26

nigelc116 wrote:
How do I test the field coil voltage?
You dont do such things on an alternator anymore. That was back in the '70-es
Any recent alternator is tested by its charge voltage over the battery poles.

But that's only a symptom of the 'modular' throw-away approach

Checking the FC volts will ensure that the battery (via its various connections) is supplying the correct energising voltage. In that case, the alternator or regulator is at fault, and can be diagnosed further. As Bonce Chops points out, there may be a poor connection giving the impression of an alternator fault.
It's a pity that fewer mechanics (DIY or professional) are prepared to have a go at proper electrical diagnostics - there's nothing very mysterious about it

It's quite simple to replace rectifier diodes, etc. as required, and to restore a faulty alternator to working order at minimal cost. I've filed up new slipring brushes before now, and they've lasted many thousands of miles, despite the manufacturers claiming that they're not replaceable.