Hope someone can help with this.
Battery sometimes goes flat overnight.
Jump start with a booster pack doesnt take much to make it start and all will be fine for the day and maybe a couple, but after a night or two back to the fllat battery.
New battery bought at xmas, alternator putting out about 14V.

Now two POSSIBLE causes
1/ when sitting stationary with car running, if I operate something reasonably high current draw, lights heater fan, electric windows etc the speedo needle jumps up (about 20mph) then goes straight back down, when driving seems ok with no fluctuation.

2/ When jumping with the pack as soon as the car starts the fans radiator fans kick in for a few seconds, also seems like they run at a fast speed for say 5 secs then a slower speed for a few more secs before stopping. Had it on my old Cos that the radiator fan switch controlling the fans failed and that used to bring the fans on at night and flatten the battery, so wonder if anyone had the same problem on a mondeo and also can the fans run at different speeds and how are they controlled.

Any pointers appreciated

Cheers

Steve

 

Have you check the voltage of the battery when the engine isnt running and ignition switched off.It shouldnt be no less than 12.6 volts.

 

Cheers

When would be best,

1/ when I come to it and its in its flat" state

or

2/ after ive jumped it and its been running and its got enough juice in it to keep restarting the car ?




And what about the alternator, it is putting out 14V ish when not loaded, maybe I should put a bit of load on it and monitor what it does when being loaded.
Is there some sort of regulator or V limiter on the alternator circuit that could be failing and also causing a spike when a load is applied which is causing the speedo needle to jump as I described, and if so could this be letting a voltage leak with a resistance so not causing a dead short but enough to drain the battery over time ? Just seems funny this has started happening and now I'm getting the flat battery problem.

Also what about the fan issue, I will try a further test at the weekend, but does anyone know if say I was to disconnect and reconnect the battery (simulating the battery going flat and me boosting it with my jumper) the fans come on straight away for a short period (seconds, maybe 5-6 ish).
Cheers for input

Steve

 

Boot light can be a issue on these, not going off when boot is shut. Sounds like bad earth or dodgy/dirty connection if the fan is kicking in the moment the battery is bought back to life, disconnect the fan before u leave it over night and then see if its flat in the morning?

 

Yep, was gonna try that at the weekend when not using the car for work , BUT spose I may as well try it tonight and then if it is that and it works I wont have to jump it tomorrow lol

So I am right in thinking the fans shouldnt kick in when the battery gets power back then

Steve

 

Self explanatory really? If you put juice into the battery when its dead and the fans fire up for a split second then obviously that points to the problem, bad earth, wiring fault? unplug the fans, or take the fuse out (in the engine bay passenger side, its one of the yellow square ones with a clear plastic top, sometimes held in with a bolt) then see if it does it .

 

The fans on your model could either by controlled by the traditional switch (Like the Sierra) or by the ECU, in any case it's most likely it has dual speed fans and so low speed and high speed there are usually two relays as such. Have you checked the alternator UNDER load?

If fans are ECU controlled which I think they will be tbh and it's gets that flat it may be it powers them on when restored, if it's only doing it when power is restored I would say certainly.

If it's going flat when left then either something is draining it (Check the boot light as said) or the battery can not hold a charge, despite it being new.

You wan't to check the battery voltage both when the battery is charged and when it's flat to see what state it's in.

EDIT: To add it's worth doing a draw to to see how much power is being pulled from the battery with everything is switched off.

Martin

 

Have already checked boot light as that was one of my first thoughts, checked it as soon as had jumped it so power back on and went in thru back seats and it wasnt on, so it wasnt on in the same state as when the battery had died over night.

Havent checked the alternator under load yet, was gonna do that today but when went to get my multi meter /clamp meter they are in my other car I havent got access to at the moment , so will bring my work one home tommorrow and have a look at the weekend

Ye when the fans come on just after jumping they are deffo running for a few seconds at TWO speeds, first for a few seconds then slowing for a few more seconds then finally stopping, so that means they are ecu controlled, and could just be the norm they come on when the ecu is given the proper power, would there be any way to prove that, at work we look at the logic in plc's all the time and thats all the ecu is, so would be nice to see what the code is behind the fan control lol.

will see what I can find out at the weekend re alternator and loadings and mess about with the fan then.

Any ideas on the speedo jumping issue, related maybe or totaly unrelated and a known issue ?

Steve

 

I assume you have air con ?, if you don't the fans are single speed.
The mere fact that the fans operate suggest a major fault is logged in the ecu, as this is safe mode, it will also bring on the fans if you disconnect the plug for the ecu cts with the engine running, but stop when replugged.
Has the battery had any knocks ?, a broken bit of plate can cause this, as it moves under the rest of the plates in the cell it causes a short, which can cause the speedo to jump due to a voltage spike, as alternator tries to overcome short, but another corner, bump etc and the bit moves, so does the short.
Pure luck where it is when it comes to a stop overnight.
Rare but does happen, my dad had one, oddly enough on a mondeo as well, with a battery from wilco, who kept refusing to change as always registered ok by the time it was at the shop, but was defo faulty, and of course the fault went when the battery went and got replaced.
The other suspect I'd be looking at is the alternator, even though charging correctly the diodes(one way electrical valves) can be leaky.
tabetha

 

Just sounds like a dodgy earth to me as i keep saying, or weak battery/alternator isnt doing its job. on my mk2 when i had my music turned up with sub and amp the headlights used to flicker to the beat of the music, dash lights, needles everything. that was the alternator about to give up the ghost. make sure the alternator belt is properly tight, i know there on an auto tensioner but if the tensioner is weak then it wont be gripping properly.