Fiesta Mk6 alternator question

[Ralphthemouth]

Hi. Just wondering if I could get some advice.

I've just got a 2008 mk6 fiesta 1.4 zetec. I had some battery troubles after buying it and connecting the radio up (6000 ford radio that was unplugged). Left for 3 days the car was dead. Unplugged radio and left for 3 days, all was fine.

So I did some checking, and after recharging the battery it was 12.5v. After 3 days with radio unplugged it was 12.3v

I checked the battery drain and it was 0.13amps. With the battery plugged back in it was still 0.13amps. With the engine running it was 14.2v. With everything on (heated front and rear screens, lights ect) the alternator charge was 12.1v. So whats happening?? Is the radio defective or is the alternator bad? The car was only ever used for short journeys by the last owner as it's only done 36k miles.

Thanks.

 

 

[stef123]

Sounds like the radio was unplugged for that very reason as you have discovered. 

[Tdci-Peter]

4 hours ago, Ralphthemouth said:

battery drain and it was 0.13amps. With the battery plugged back in it was still 0.13amps. With the engine running it was 14.2v. With everything on (heated front and rear screens, lights ect) the alternator charge was 12.1v.

Sounds a bit like a combination, at the moment.

0.13A for 3 days is over 9AH, that is quite a big chunk of charge out of the battery. However, that standby drain often drops after some time (minutes or even hours), as the car goes into long term standby mode.

Re-try the alternator charge test with just normal winter driving load of headlights, heater fan & wipers. The heated screens may be a bit much for it, they are not intended for long term use. And make sure to test at the battery terminals, there can be some quite large voltage drops in the car wiring under heavy load.

14.2v is a tad on the low side, 14.4 to 14.8v is really needed to fully charge a silver calcium (normal Ford) battery.

 

[Ralphthemouth]

Many thanks. It's a Bosch s4 battery that's in there now. Previous receipts show that it had a new battery in 2009 and another in 2012. Possibly due to the short trips the previews driver did. I'll re check it without the big power units on. Thanks for explaining the stand by mode. I only checked it about 1 min after locking the car.

 

[Stuart35]

I had a similar problem. It was my bluetooth module not sleeping.

[Ralphthemouth]

I don't have bluetooth installed. But I've got a new radio to try. 

[Ralphthemouth]

Ok. So I've got a new radio in. I checked the amps drain after waiting about 15 mins for the car to shut down and it was a good 0.06amps. Under load, without the heated front screen the battery was a good 13.5v from the alternator. I've just checked it and now the battery is showing 12.1v after sitting for 24hrs. So I can only assume the battery is bad? Can the alternator drain the battery on an intermittent basis? As when i left it for 3 days last week without the old radio plugged in, it was 12.3v after 3 days. I've got an led interior light that glows all the time,  but it was doing that when I registered the 0.06 amp drain.

I've connected neg probe from neg battery and +probe to alternator housing = 0.06v

Neg probe to +battery and +probe to alternator wire and nut and stud =0.03v.

Is that right? I don't really know how to check the alternator. 

[Tdci-Peter]

13 hours ago, Ralphthemouth said:

Under load, without the heated front screen the battery was a good 13.5v from the alternator. I've just checked it and now the battery is showing 12.1v after sitting for 24hrs

13.5v is not enough to charge the battery in any reasonable time. It needs over 14v, probably 14.4 to 14.8v to get it back to full charge, for at least an hour. The 12.1v suggests it is being maintained at 50% charge or less.

The readings over the wires from alternator to battery look ok, assuming they were taken under the load situation you described. It is hard to test these alternators, mis-diagnosis is frequent. They use a signal from the pcm to control the charging voltage, and are not self-contained like older ones.

I recommend getting one of those cheap cigar socket voltmeters (eg from eBay / Amazon), comparing its readings with the voltmeter on the battery to check it (there will be drops in the car internal wiring, as well as meter accuracy), then observing it over a period of time.

If you are not seeing well over 14v (as at the battery) for a significant time, then the alternator is suspect. But I have seen occasions where the alternator is changed without effect. It seems the pcm is not commanding the right voltage from it. I know of no cost effective way to deal with this, weekly charging or a solar charger may be better than meddling with the pcm.

The engine coolant temperature sensor is worth checking (does the temp gauge read sensibly?) as this system puts out max voltage when cold, and can cut it back when hot.

 

[Ralphthemouth]

Thanks Peter. I'll continue to check on the problem. The Mrs is using all week now for work so it might not be sitting for long enough to drain the battery. (Until a holiday). Funny enough, i was looking at solar chargers last night. I appreciate your help.