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Discussion Starter · #1 ·
I'm trying to solve a bit of a puzzle with my A/C. It wasn't working well today and I recall reading the thing about blowing off the valve on the compressor and thought that attention to avoid that would be good.

When I first got the car, I took it to TrentSaab who commented that it was a little odd that the radiator fan came on with the compressor. The problem that this causes for me is that it's two loads at the same time and really slugs the engine and can stall it when the A/C compressor is working hard.

I lived with it but then when the head gasket was fixed, somewhere along the line, the behaviour was changed and the fan no longer came on. At first I thought "this is good, no more slugged engine" but of course the upshot is that there's no airflow at low speed to cool the A/C radiator either and hence poor A/C.

This evening I had a bit of a delve around and found a black wire which was tucked neatly back into the long sleeving which the garage must have done when they wondered what this wire was for. I traced it up to what appears to be a relay under the aquarium and indeed, if I wire this in parallel with one of the engine radiator coolant switch terminals, I'm back to the fan coming on with the compressor.

I'd really like to nail this one properly though because that does seem wrong and if I turn the ignition on and press the frosty button on the dash, the behaviour is that the magnetic clutch on the compressor engages and the fan comes on. Not exactly what you want when starting the engine.

I also found a thin blue wire exiting the loom with a bare end at the same exit where the wires to the radiator switch also exit.

It gets better, under the aquarium, the low pressure switch on the dryer has four wires, the green ones are cut off right at the connector and hence go nowhere.

I'd like to know, when is the fan supposed to come on in relation to the compressor clutch on manual A/C? Answers of "intermittently" won't help here, I need specifics, it seems like there ought to be a short delay or based on some other sensor so that both aren't operating at the same time.

Can anyone provide a schematic because Haynes has nothing on this.

Thanks

David.
 

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David

If you take the offside headlight unit out you should be able to see the acc metal hoses - follow them down to your left (as you are looking in from the front) and tucked down on the inner wing towards the bottom of the engine is the a/c pressure switch which on my two 9000s is in a block on a small cylinder. Its a well known problem that the cables from here tend to develop breaks (but on both my cars you can't actually get any access to the actual wires so its not possible to test them easily) which can lead to several problems.


Steve
 

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Discussion Starter · #4 ·
Hmm, I'll look again but I definitely have two blue wires just below the left hand hose going to the lower condenser connection and one of these is floating around doing nothing.

Looking at the circuit diagram I found, these blue wires should go to the pressure switch.

Is yours a manual AC or ACC?

Failing any success on this, I'll just make up a time delay box to introduce a few seconds delay to give the engine a moment to recover from the compressor engaging to the fan starting as that's the real problem when the engine gets slugged with both especially if you bite the clutch at the same time and end up with a stalled engine.

David.
 

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Discussion Starter · #6 ·
Thanks col, that's the wiring diagram I found and posted the link to above. It does help in that I have identified that there should be two blue wires going to the pressure sensor but i'm going to post a pic of behind the headlight because I certainly can't find a pressure sensor but can find a couple of blue wires, one of which is floating free.

David.
 

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Discussion Starter · #7 ·
Ok anyone for a challenge? Here are three pics to see if anyone can help on this, sorry about the size, I wanted to keep the detail. Firstly the picture behind the headlight, there's nothing that I can see that resembles a pressure switch in the AC hose and I can assure you that there's nothing on the bottom of the condenser either (unless I haven't felt along the right part yet?) The part of the loom where the orange wire breaks out to the compressor (middle top) is where the wire in the loom is the black wire that goes to earth when the compressor is engaged, that is now wired across the coolant sensor so that the fan comes on with the compressor (how it was when I got the car).



Next pic is the bottom of the condenser, you can see the blue wire, one of which goes to the coolant temp sensor and the other floating around. That's where I think the pressure sensor should be and that's where it's shown in the EPC diagram for a 1993 manual AC so I'm wondering if the condenser has been changed at some point?



Final pic is the aquariam and this is a confusing mess! What's going on with the wires cut off the connector block to nowhere? The green wires are cut off, the connector doesn't go anywhere and what do the blue wires do anyway? There are four connectors in this area that don't connect to anything which doesn't make it any easier.



I am beginning to suspect that the condenser has been changed at some point and that there was no pressure switch and hence the system has been arranged to work in the manner in which it is now functioning.
 

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Discussion Starter · #8 ·
Another question, should there be a second fan other than the cooling system fan on the manual A/C on a 1992?

The EPC shows one and the circuit diagram references lists two fans, one for cooling system and one for A/C.

This really looks like someone has swapped some bits at some point.
 

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David dunno if this is of any help but my 9000 is my'90 with manual a/c.Had a look earlier and has only one fan.Have never heard it cut in with a/c on yet. Will have a look at wiring to see how yours compares to mine.
Col
 

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David, I very much suspect that the pressure switch is the thing in your last photo with two blue and two green wires coming out of it. It should have two switching functions: a low pressure switch that prevents the system running if the gas pressure drops. This is to stop the compressor eating itself if you lose gas and hence the lubricant with it. A high pressure switch (presumably the blue wires) turns on the cooling fan when the system pressure gets dangerously high. I looks like someone has bodged the system, either because the high pressure switch has failed, or because they didn't understand how it works. You should be able to test the low and high switches with a meter. If the high pressure switch has failed, replacement means degassing and regassing the system (and hence a few quid!), so perhaps that's why it's been bodged. The default otherwise is to run the fan continuously when the A/C is turned on. Do not be tempted to run the A/C without the fan operational (other than for a short time to test the high pressure switch) as you run the risk of blowing the rupture (safety) disk on the back of the compressor. If you do test the HP switch, you must disconnect the fan, as the system pressure may not get high enough with the fan running. Also, if you are low on gas, the system pressure may not get high enough, leading to the false conclusion the the switch is faulty. Clear as mud?
 

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Discussion Starter · #12 ·
Col, I'd check things out because the main reason I'm doing this is because my cooling fan (the only one I have) wasn't cutting in anymore on A/C, the output pipe of the condenser was very hot and hence not being effective by the time time it delivered hot R12 to the evapourator and I'd read the story about the high pressure switch not being operative and didn't want to chance blowing a working system.

Here's why I continue to be confused over this, this is a picture from the EPC clearly showing a second fan for the A/C.

Mark, i'm taking the note about not running the A/C without the fan seriously as I think it was your other post elsewhere that got me thinking on this. I was aware that my fan was no longer working after getting my head done last year (yes that long but it's only just got warm again right and I was driving my Aero during last summer).

What I'm curious about, is where that connector block on the pressure switch in the aquarium is supposed to go to?

Thanks for all the help on this one by the way chaps, i'd love to see some pics of a correctly set up manual A/C!
 

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I have no specific experience of the Saab manual A/C system, but most A/C systems have bascially the same components and controls. Although the picture shows a second fan, I'm not sure that this means that all cars in all markets should have one. The 1994 CSE handbook shows a second fan, but it's only in certain (quite warm) markets. Assuming your car is similar to the later cars, the radiator fan is driven by a relay (or two relays if it's two speed!). The wiring is quite simple. The low speed relay can be switched on by either the rad temperature switch or the A/C high pressure switch. These switches are simply wired in parallel. If you can find the relay, and work out which is the wire to the rad switch, there should be a second wire on the same terminal that should head off to the high pressure switch. I'm not sure whether it's positive switched or earth switched though, but you will be able to decided very easily with a meter.

P.S. The fan relays are in a box by the battery, at least on the later cars.

P.P.S. If all else fails, if you can get a recommendation for a local aircon expert they are normally not that expensive.
 

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Discussion Starter · #15 ·
Well as far as I can tell, the cooling fan is single speed, i can't say I've ever noticed a second speed anyway.

I did measure the behaviour of the blue wire that's floating but that doesn't seem to do anything so maybe the high pressure switch is faulty or it's no longer in the loom given the other "interesting" bodges.

Do you know if the low speed fan is acheived by a big resistor? If so, I might add that relay and work something in.
 

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Originally posted by David Taylor:
[qb]Do you know if the low speed fan is acheived by a big resistor?  [/qb][/b]
See item 14 (or is it 13A?) in your picture above. It's a large, often gold coloured, resistor normally fitted so that it's in the airflow of the fan. If the fan has two wires, it's single speed, three wires means it's got two speeds.

From your photo, I suggest that the high pressure switch isn't connected to anything, as the connector block is flapping in the breeze.
 

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Discussion Starter · #17 ·
Yes certainly on mine they're flapping around but given that the fan is wired to come on with the compressor I don't think there's any chance of being under cooled.

What I was considering was wiring in a low value high wattage resistor just to lower the speed when the AC is required, just to cut the load a little to the engine when both cut in.

Anyone know offhand what value the resistor is?
 
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