Cooling Fan / Aircon Advice

[Robatron]

Hi guys,

Firstly, I wasn't entirely sure which section to post this in as it could fall into Aircon or Electrical problems.

Anyway, here's my problem:

When the car get's to the normal operating temperature (90 degrees), the cooling fan kicks in to cool the engine down. This in itself is obviously a good thing but recently I have noticed that when this fan kicks in the aircon turns itself on for the duration of the cooling period of the fan.

Just for the record, at this time of year I don't use aircon but you can really feel it kick in as it saps so much power. The lights on the Aircon switches do not glow red as they have not been depressed.

Before anyone says anything, yes I do know that when the aircon is turned on the cooling fan also runs but I'm pretty sure that the aircon shouldn't switch itself on whilst the cooling fan is running.

I've had a look on the lid of the fusebox and figured that there were 4 possible relays to check, the first two being for the cooling fan and the other two being for the aircon and they all use 214 relays. I've pulled a 214 relay out of my 8v coupe and replaced each relay one at a time to see if this solves the problem and much to my annoyance it hasn't.

Has anybody had any similar experiences or can anybody advise as to where I should start looking next?

[S2central.net]

What year is yours - I look at the wiring later today sometime and see if I can smell a rat...

Firstly your radfan shouldn't be cutting in at 90 degrees - thats too low, but when the fan comes on it shouldn't activate the aircon. Seems like some errant wiring somewhere.

[Robatron]

It's a 91 3B.

Sorry you're right Paul, it cuts in after 90 degrees.

Thanks!

[S2central.net]

I only have official schematics from 1992 at the moment, but I'm pretty sure the 1991 cars had different wiring in this area... Going on a partial set of Norwegian '91 3B schematics that I have. I'll see what gives - I'll need to get you to pull some relays to check this further.

[Robatron]

Not a problem, I brought the car into work with me today so it's sat outside at the moment.

[S2central.net]

See this page for 1992 manual aircon...

http://www.s2central.net/S2_Schematics/D/D35.PDF

NOTE - Error on D35/2 with J101 shown in position 3 – should be position 11.

[S2central.net]

To check if this schematic is anyway usable... In your main relay panel -

Pulling Relay 11 should stop the fan running (Hi Speed #1)

Relay 2 would stop fan at Hi Speed #2

Relay 3 should stop afterrun - and prevent the test of afterrun pump when you turn the key on

Relay 6 should stop the cabin fan

[S2central.net]

Hi Speed #1 is the fan speed for the 1st high temp switch - F18. This speed is also used when the aircon is ON.

Hi Speed #2 is activated by switch F54.

You can bridge the terminals at F18 and F54 with care to check they are working as they should.

It seems like your F18 is coming on too early... unless you have some sort of circulation problem whereby the water temp at that point in the radiator is very different from what you see on the gauge... Of course your F76 might be giving a low reading also.

[S2central.net]

Looking at the circuit for Hi-Speed #1 you can see there are two ways to activate Relay 11.

1. F18 closes with high water temp
2. The aircon is activated... Note the diode J28 which forms the one way link from the clutch controller

Assuming there is no damaged / bridged wiring - need to check a few more things... If you remove the Relay in position #4 at the drivers pedals that will stop aircon coming on - it essentially controls the magnetic clutch on the compressor. So when you get Fan onto Hi#1 then your aircon should stay off.

Either that clutch control relay is bad, or the one-way circuit in the shape of J28 has failed closed and is contributing to the problem... Dunno if backward signalling to the clutch relay would activate it but its an odd one... If the clutch relay was always stuck on then aircon and radfan would always run - there is maybe some badness related to J28 and/or the wiring that links it to between the relays.

Best way to check the wiiring is to remove ALL related relays and buzz out the circuit carefully as per the schematic - IFF the schematic is right for your 1991 car of course !!!!!

[Robatron]

Thanks for the info Paul.

Would you be suggesting that I may have a blockage in the cooling system? On a couple of occasions on gentle revs I can hear what I can only describe as water being pulled/sucked from somewhere.

I have a Digital Temperature Gun which I can use to see if the temperature is consistent throughout the system.

[S2central.net]

You might have some sort of blockage or air pocket... Bit unusual for air pockets to stay for a long time.

Pull that relay #4 under the dash and verify the aircon stays off as well.

[Robatron]

Hmmmm, I'll check out the Clutch Relay too.

This is top stuff Paul!

[Robatron]

Paul, I'm going to have a play at the weekend as I won't have a chance to make any headway before then. I'll report back with my findings.