Air con / Aternator fault BECM?

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Jim M

New Member
Posts
6
Location
Bedfordshire
Hi Guys, hope someone can help.
Just recently my p38s air con is only blowing cold when the engine/system is cold, as soon as the engine warms up it stops working and the book light has come on once (last sunday when it was really hot outside), the clutch is engaging, Ive had it regassed and checked for leaks but all ok, thought it might be pressure switches? And now I get alternator fault coming on sometimes when the ignition is on and engine not running, and the charge light and alterntor fault have come on with engine running but intermittantly, then once turned off and try to start again it acts like the battery is flat. Quick jump start and run for 5 mins no warning lights on, turn engine off and starts again easily. Could it be the Becm playing about?
 
Sounds more like a duff battery - the P38's hate weak batteries....

As for the HEVAC fault - sounds like a Blend Motor....when you select a higher temperature - does the outlet temperature change in comparison??

The P38 uses 3 motors to adjust temeperature and distribution....if you are only getting luke warm air and the temperature doesn't change on demand - one or both could have stalled or gone U/S....

If the temps do change on demand - yet still no cold output - could be the expansion valve....you say you have regassed it - and whilst the clutch shouldn't engage on the compressor if there is no gas pressure - it is not unheard of....
 
If I turn the heaters up then they do blow hotter. The pipes coming out of the compressor start off with one hot and one cold and once things have warmed up they both are hot. the condensor fans cut in this afternoon but cant remember them cutting before. I'll check the battery (didnt think of this as its quite new, but it is halfrauds!)
 
Halfrauds batteries are normally OK. If it isn't charging it may well be the alternator (or belt) is on its way out. Think the alternator should be chucking out about 14 or 15V when charging?

Alternatively, could be a bad earth strap somewhere. If it is saying alternator fault I think I'd start there though.
 
If it say's alternator fault, you can bet you have a duff alternator especially as you have also had a flat battery.
The other possibility is bad connections or the underbonnet fuse box, check for signs/smells of burning/overheating.
 
Checked the battery and alternator today, the battery is reading 12.6v and stands up to a drop test, the alternator is pushing out a steady 13.9 volts. Haven't checked the under bonnet fuse box but it looks quite new, will try and check it out tomorrow. Is there any other ideas ?
 
The alt should be putting out 14.2 sounds like poor connections had an issue with battery connections the lead had corroded internally so only worked at random might be worth a look also recheck the fuse box they corrode really badly
 
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