Technical Alternator ok, battery ok, battery not charging

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Technical Alternator ok, battery ok, battery not charging

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Feb 26, 2008
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My wife drove from the station, about 20mins, very hot day. I got in the car and the idle is rough, which is new to me, but she says it's been like that for a while. I drive maybe a mile or 2, in slow traffic, the temp keeps going up (which is normal) but after a while I get a 'shooshing' noise at about 100-110c indicated on the guage (this is a standard Cinq btw), I also don't think I've heard the fan kick in, at some point the battery warning light comes on, but the engine keeps going. At some point while we're driving I turn the heater on full and the interior fan. I decide to abandon our trip, pull over, takes a good 5mins from the needle to come off the 110c point, it comes down to 95, I then drive home no traffic, decent flow of air. No temperature issues on the way home.

Now ever since the above, the battery warning light stays on after I start the engine up. With or without the engine running I have 12.5v across the battery, so it's genuinely not charging. The drive belt is intact and I think the altenator (which is new to the car, and I think a new part) is ok.

One other thing, I started the engine and ran it for 2.5mins, no change to the temperature of a radiator hose.

I think perhaps the thermostat has failed closed, and that caused the initial overheating, but it seems that something has failed causing the charging problem, but not being mechanically minded, I'm cluless as to what!? :confused:.

Any ideas, please?

Marc
 
check you have coolant in the header tank, if it is not at normal level add coolant to max mark and open both bleed screws until you get coolant out.
don't try this if engine is warm...

If you need to add coolant the it has probably escaped and flooded the alternator you can try WD40 straw in end remote from belt just it case the brushes have lifted

if you have a soft face hammer a tap on the aluminium casing of the alt is last resort before remove and fettling.

also remove cable form from temperature switch on rad and short connectors in cable with bent paper clip the fan should run before doing this check the fan bearings are ok allowing free spin. if the fan turns freely but does not run there is a fuse and earth point to check

put wife over knee and hit hard for failure to relay complaints from wee auto...
 
For the battery/alternator thing, check that the small cable to the alternator is intact and actually connected (it's a lucar at the alternator end, so easy to inadvertently pull out). If it becomes disconnected, the battery simply won't charge.

One thing though, that alternators hate, is being soaked in hot coolant.

The cooling issue needs further investigation: if the cooling fan isn't coming on, you'll kill the head gasket.
 
there should be two wires connected to the alternator
 
Thanks everyone. The lack of charge turned out to be an intermittent alternator fault (the battery warning light had been on ever since the indident, as we drove to the garage it went off and stayed off!). The alternator was a recon one put on in 2011. As well as that, the fan switch was not working.

There wasn't AFAIK, any actual coolant spray over. After the car had cooled down, I checked the coolant level, and it was normal.

I can only think that the engine bay got so hot it somehow caused damage to the alternator, but it sounds a tenuous theory!

Anyway, new switch and another recon alternator and it's now ok.

Apparently the temp guage is reading high, so now I'm off to see how hard that would be to replace ... :)

Marc
 
The temp gauge problem could be the sender rather than the gauge...
 
Id assume the meter and sender was ok as the cooling system may get unhappy at 110C, even if it should really be able to tolerate 110C as the coolant has a higher boiling point than water, and it is under pressure, if the system is not leaking.

But Id check for leaks, if there was a smell of antifreeze, and even if there was not a small, buy a new coolant cap, treat the old cap in kettle descaler suitable for plastic kettle, and keep it in glove compartment as a functional spare. The cap needs to hold down one bar, and can go off spec with contaminants from the coolant.

The auto shop should really replace the coolant after either two or five years and flush it out properly, you can get proprietary flush treatments for mixed metal engines.

Noel
 
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