THE RADMAN

iTrader: (2)

on a p8 esc cos,what exactly does the chip have to do with regards to the aircon system? as far as i can make out there are 2 pins on the ecu,pin 21 from the pressure switch and pin 12 which is an earth from relay no11?i know the ecu increases the idle speed slightly to compensate for the aircon system running but how does the earth from relay11 work? any experts out there? think im getting there now

Dave Henshall

the ecu doesnt do anything to the aircon, the aircon puts a ground to pin 21 when its on which makes the ecu open the iscv to allow it to rick over faster, thast all IIRC, also, not all p8's are air con compatible

Azrael

Some did run ALS instead, didn't they?

sailorbob

Not sure about the P8 but in addition to the raised idle (to cope with the extra load) most ecu's also cut out the aircon compressor briefly at WOT so more power goes to the wheels instead of the accessories.

THE RADMAN

iTrader: (2)

mine doesnt cut it out at all wheres stu when you need him,lol

markk

iTrader: (2)

THE RADMAN

iTrader: (2)

up

THE RADMAN

iTrader: (2)

can someone tell me exactly what the the ecu does then in regards to aircon? and are there diff versions for aircon model? dont want to start ripping wiring apart if its just the chip/ecu

Dave Henshall

when the air con is switched on, it connects (though a relay) an earth to pin 21 of the ecu, this (if the ecu is an aircon ecu) will raise the idle speed to compensate for the extra load the air con compressor places on the engine... and thats it, the ecu has no feedback or control over the actual airon...

Dave Henshall

ps,, ill check that number 2nite....

THE RADMAN

iTrader: (2)

good job your here dave

THE RADMAN

iTrader: (2)

did u get the number?

Dave Henshall

sorry bud - ill get it 2nite - ended up lookin at bathroom suites

velocity

not sure if the system hardware is the same as the 4x4 saph l8 but the pins ar the same designation as the p8.
on the 4x4 saph pin 21 should has a 12v supply from fuse 18 which is routed through an de-iceing switch in the aircon cooling plenm, this switch cuts the aircon system if the plenm ices up by removing the voltage at pin 21
relay m11 on the saph is the idle speed compensation realy for the aircon and is earthed through pin 12,and this in turn gets its supply from the magnetic clutch relay.
i can send you a copy of the diagram if you wish it may help as the same pins are involved and i would guess that the rest of the system is similar.
its possible you have a simple wire short to ground or just a wrong connection made

THE RADMAN

iTrader: (2)

thanks for that velocity they sound the same system alright,ive got a wiring diagram now so should hopefully be getting it sorted,the only thing i cant suss out is how the dash switch works as it just feeds the recirc,the fans and de ice switch it doesnt seem to feed the compressor at all?i presume that cutting the power to one of them must cut the compressor as well somehow?

velocity

on the l8 4x4 the switch side of the magnetic clutch relay is feed from fuse 18,this relay is earthed by the dash switch when aircon is selected.the mag clutch relay now supplies main power to the idle speed compensation relay which when energised by a switched live (ignition i think) now supplies power to the compressor magnetic clutch via two system pressure cut off switches and drives the compressor via the v-belt
i would look at the dash selector switch first disconnect it and see what happens
if the activation earthing wire from the magnetic clutch relay is shorted to ground anywhere between the relay and the dash switch it would be the same as the dashswitch been selected on all the time and asumeing all else is wired correctly and its the same as the 4x4 then it could be your problem.
having it working is a good start as usually the problen is trying to get it to work
i couldnt get mine (4x4) to activate after a full engine/car strip down and rebuild,it turned out to be the throttle position sensor adjustment it was causing my idle speed to be at 2000rpm and this confused the ecu with regards to the idle speed compensation relay.
so lets hear how you get on

foreigneRS

also, don't forget when testing that the a/c compressor should only come on when the blower is running

Azrael

On my car it's always running even when switch is in centre position on same cars I've seen it''s also so.

Dave Henshall

righty..

my ecu has the following on the sticker on the cover:


IAW048/P8

6160018105 A/C Z12V=

V92AB-12A297-AA-S04_16


however there is some biro written on there aswell (dont know who has done it or what it means but...)

the seconf line has 'A' at the end.... 6160018105A

and the third line has _16 crossed out and _17 is wittten next to it....

again dont know what the signifiacne of these is(if any) ... anybody?


eddited to say,, ive found a website that lists a recon ecu, the same details, but the middle line is 6160018103 so whether the 3 at the end is non air con and the 5 means it is...?

THE RADMAN

iTrader: (2)

right then, update time,everything has been checked out and is working exactly as it should,on off switch,de ice switch,pressure switch,wiring to ecu all tested so it looks as though the ecu isnt earthing it out to switch it off or it is the chip which isnt compatible,the ecu numbers are exactly the same as yours dave minus any biro writing,i now need to find someone else with a p8 with aircon to check their numbers as well,is yours deffo from an aircon model dave? cheers for the help

foreigneRS

how do you know that it's working? just that the light in the switch is on?

have you checked the electromagnetic clutch on the compressor? that must not engage if the blower is not running, otherwise the evaporator will turn into a block of ice and block your airflow into the cabin (not that you'll notice becuase your blower is switched off), and the low pressure side of the a/c system could go below atmospheric pressure and let air into the system through the compressor shaft seal. you can also damage the compressor through lack of lubrication.

Azrael

I ment that blower was running... very low speed at centre position but it runs

Dave Henshall

i'm not 100% sure it is as my car isn't air con, stu said the ecu was an aircon one when he converted it to coilpack as he used the aircon pin as the rev couter drive output, but like i say, as mine isnt an aircon car, i cant 100% be sure....

foreigneRS

yes, ford had a period when they set the blower to always run a little, even with the switch in the off position. was a good idea in some ways, as it stops the cabin misting up.

always annoys me as an HVAC engineer when i see people driving about with their windows dripping on the inside cos they've switched the blower off the damn thing has an infinitely variable temperature setting between cold and hot so that you can get the right temperature for you. why turn off the airflow?

Azrael

foreigneRS I cannot understand reason for switching that off too. Always runs on my cars.

_DAN_

Watching

THE RADMAN

iTrader: (2)

tried another ecu,still the same,im now looking for the aircon rad fan relay,according to my diagram there should be one,but it isnt in the fusebox,any ideas?

velocity

she exists but not in the fuse box and it controls the two fans.my diagram identifies it as vc 2245 but does not give a location.i can only assume its in the engine compartment somewhere. i have 92 ecoz wire diagrams but no diagram for the aircon.
but i see a mention of aircon fan on the the one of the diagrams tied in with the cooling fan relay.
from what i can gather,fuse f25 supplies power to activate the relay which is earthed by the temp switch.so if pulling this fuse stops the fans (if that whats running)then your relay is getting a signal to opperate or a short to ground somewhere
also when you find the relay if you can identify i think pin 9 brown and yellow wire (should be one of the corner pins on the relay) this appears to be the control or drive for the aircon motor,my diagram fails me at this point
if memory serves me corectly there is a main fuse box in the engine compartment near the battery which has large type fuses in it.locate this and pull fuse D, this fuse supplies main power to drive the cooling fans and they should defo stop.but dont forget to reinstall it as your cooling fans will not work and we dont want to nuke the head
if you could tell me exactly what is running ie one fan,both fans,compressor,everything.also what lights are on if any.
hope this is some help
ps just got your pm now

Dave Henshall

ive just had a look through my new escos wiring diagrms

and gues what, the air con one is included (1993)

ill copy it out and post it here...... in afew mins...

Dave Henshall

looks like there is a connection to pin 12 aswell, is also looks lie there is a relay that when teh throttle is pressed all the way down (WOT) it kills the air con aswell.... every day is a school day

you may have to save them and print them out and stick them together to make sense of them, all 3 overlap each other

foreigneRS

most cars have that feature to make overtaking safer

velocity

good man dave thats the very diagram i,m missing might get to the bottom of this problem at last

Azrael

I don't think small turbo has that. It's nice inside even when I swich it on on the track.

foreigneRS

i suspect that it has

Azrael

foreigneRS so how it keep interior cool, only by switching on in corners?

Dave Henshall

as a occupant of the car, yuo wouldn't actually know it had switched off,

like rurning the power off to your fridge, it remains cold for some time afterwards, as does the cooling coil of the AC

Dave Henshall

and its only when the throttle is actually wide open,

sailorbob

The WOT a/c cut out is on a s/w timer so if you stay at WOT beyond that time the a/c comes back on (which means it's adjustable by means of a chip )

Dave Henshall

Azrael

Now that explains things On the track you are most of the time at WOT.