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Discussion Starter · #1 ·
Since I have a 1993 900 with the 2.1, I decided to do the cooling fan mod. I obtained the replacement relay and did the splicing with the oversight of my mechanic friend, because I just wanted to be sure I did it correctly. Long story short, after I did the splice, I shorted the terminals for the thermoswitch and it worked. Great!

Last weekend, I decided to replace original Saab radiator with a Nissens, along with the correct 89 degree thermostat (previously had the 82 from the PO) and a 92 degree thermoswitch, because I believe in the Saab engineers. I drove it home from work on a 90 degree day and it was working well overall, but on the final leg, I could see the temp was creeping up more than it had been previously. Once I got it in the garage and popped the hood, I saw the driver's side primary cooling fan was not running with the AC fan.

I removed the primary cooling fan, tested it and it worked with 12 volts applied to it. So the fan is fine. I then checked the fuses and both fan fuses were good, too. I tried swapping out the new cooling fan relay for another of the same type and still, only the AC fan ran when the thermoswitch terminals were shorted. I'm absolutely perplexed and am trying to see if I can make some headway before my previously-mentioned mechanic friend can come by on Friday evening to look at it with me.

The weather is great out, for the first time in a week, and I'd really like to enjoy my 'vert before Friday night! :cool:
 

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either your temp sender in no good or is it too high a rating but not sure what it should be, but it does have to get to a high temp 92 before it will kick in and this usually means the dial on dash has the needle above the normal middle area but if you are worried about overheating remove the two wires from the sender unit and join them so that fan is on all the time, and just disconnect when you turn engine off, as it's only for a day and won't hurt anything, or rig a switch and lead into the circuit so you can operate it manually.
 

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92* C is about 198* F...seems pretty warm for a summertime kick-on of the fan. I'd run that in the winter but 88* C is about 190* F and that's more my comfort level (others may disagree) for a hot midwest summer.
 

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Discussion Starter · #4 ·
Unfortunately, although I did hold onto the old thermoswitch, it might only be the 82 degree one (will have to double check). Obviously, if I put that one back in, it might end up conflicting with my 89 degree thermostat. Still, that doesn't explain why after the dual fan mod, only the AC fan runs and the primary one no longer does. Of course, maybe I'm overlooking something obvious.
 

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Unfortunately, although I did hold onto the old thermoswitch, it might only be the 82 degree one (will have to double check). Obviously, if I put that one back in, it might end up conflicting with my 89 degree thermostat. Still, that doesn't explain why after the dual fan mod, only the AC fan runs and the primary one no longer does. Of course, maybe I'm overlooking something obvious.
I would put the lower temperature one in, even if temporarily, and see if it kicks on both fans.
 

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Discussion Starter · #6 ·
I would put the lower temperature one in, even if temporarily, and see if it kicks on both fans.
I checked the part number on the old one. That was also a 92. I put it back in with a new sealer gasket and it's behaving the same way. Must be a relay or some wiring. And, to boot, it's also wicking coolant from the gasket, just like the old one was doing.
 

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I'm not familiar with this cooling fan mod you've done, but it sounds like something in the wiring is wrong. I'd go through the instructions and check the wiring all the way through.
 

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Concentrate on the actions you have done to modify the relays and wiring. Something has changed or come loose or not held up to the task, so only worry about getting this stable.
Don't meddle with anything else until you have the basic core fan operation sorted.
and a 92 degree thermoswitch, because I believe in the Saab engineers
....uh? What was it before?

Radiator Thermoswitch "acts" (closes, connects, shorts, whatever term you want....) when the coolant on the LH side of the radiator EXCEEDS ~95-96 degrees C. Thermoswitch "relaxes" when the coolant is recedes BELOW ~92 degrees C.

For what it's worth.....Temperature sender for the gauge has nothing to do with fan operation.
If you want complete faith in the gauge readings, qualify the accuracy by using some resistors. Disconnect the temperature sender on the head. Connect a 22 ohm resistor to the wire and the other side to the block. Turn on ignition, Temp Needle should be on the RED mark of the gauge. Connect a 47 ohm resistor and connect the same way as above........needle should hover just below half scale deflection
 

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Discussion Starter · #9 ·
I did get the coolant leak fixed, I think. So at least that's a non-issue. Just got to figure out why the primary fan isn't working.

FYI, here's the bulletin for the fan mod that I mentioned. It's listed in Townsend's site under the cooling system maintenance section:

http://townsendimports.com/Web/cooling_system_folder/hightempsbpg1.htm

The thing is, the mod worked before, I verified the wiring was correct before soldering. I'll have to recheck the wiring and the solder, I think. It shouldn't be the relay since I swapped in a different one and even tried it with the old (pre-mod) fan relay that should only activate the primary fan and it behaved the same. I'm sure there's a very logical explanation here... :confused:
 

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Your fans aren't working right. It has nothing to do with thermostat temperatures. Find out what you did wrong and make it right.
If it's working right, it can idle all day or go 100 mph all day in Death Valley with no cooling problems, with original 89 and 92 thermostats.
 

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Discussion Starter · #11 ·
Your fans aren't working right. It has nothing to do with thermostat temperatures. Find out what you did wrong and make it right.
If it's working right, it can idle all day or go 100 mph all day in Death Valley with no cooling problems, with original 89 and 92 thermostats.
Jim, I agree with you 100%. I've read your last word on cooling system/engine temps and a number of other extensive explanations. I believe that you only need an 89 degree thermostat and a 92 degree fanswitch, which is why I ordered my replacements for the stock specifications (I don't know why the PO would have an 82 degree thermostat and a 92 degree fanswitch). Now that I've already gone and spliced my wires so that both fans come on, instead of the primary one only, I have to retrace my steps to ensure they work in tandem again. In my eyes, it seems like a waste to not use the AC cooling fan, since my AC system is on the fritz and I don't use it.

Honestly, it shouldn't be necessary in a healthy cooling system, but if Saab put out a notice to essentially retrofit the system on my 2.1 to become like the one on my previous '89 2.0, then I don't see anything wrong with doing that. Basically, given the symptoms, I just don't know if the problems are at the splice/solder or with the relay, since I have no reason to think the wiring harness has somehow failed in the mean time.
 

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2.1's have a reputation for popping head gaskets. This might be the reason why Saab issued the bulletin. On my Turbo,since I pulled the a/c, I've been going back and forth with wiring in the 2nd fan or just pulling it altogether. My thoughts about wiring it in would be to get air flowing across the turbo. My thoughts against it is the wall of heavy plastic and metal fan doodads in back of the radiator that block air flow through the radiator. I'll let you know which of the voices in my head wins ;)
 

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... but if Saab put out a notice to essentially retrofit the system on my 2.1 to become like the one on my previous '89 2.0....
SAAB never "put out a notice to essentially retrofit the system". Reread the first three paragraphs of the Service Bulletin.
It says if you have a picky customer, you can do this if you want, SAAB will pay the warranty claim.
The confusion about correct interpretation of bulletins by laymen is the main reason manufacturers would prefer that they not be made public.
A new SAAB 900, with no modifications whatsoever, would work fine, indefinitely, whether idling or driving 100 mph, in the hottest place on earth; it won't overheat. If your car won't do that, it needs repair, not modification.
2.1 engines didn't pop any more head gaskets than any of the other models, but I can't argue with the internet, y'all do what you want.
 

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Discussion Starter · #14 ·
I'm not disagreeing - I simply want my cooling system to work as closely to stock as possible. If a new radiator, thermoswitch, thermostat and coolant doesn't keep the temperature in a moderate range, the only weak link left would be my water pump. Regardless of what Saab says, I am not really sure why they would have changed the function of the cooling system from both fans working together to just the one primary cooling fan for the latter years. If you don't mind me asking, in your experience Jim (and maybe it varied slightly from car to car), what was the typical temperature range for the cooling system indicated by the dash gauge? It's possible after the new components and fresh coolant that my cooling system is working as well as it's supposed to. It's not as if it's overheated yet. As far as the 2.1s go, I don't think they're any more prone to blowing their head gasket as the 2.0s are, barring lack of maintenance for either.
 

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I'm not disagreeing - I simply want my cooling system to work as closely to stock as possible.
Then why modify it?
If a new radiator, thermoswitch, thermostat and coolant doesn't keep the temperature in a moderate range, the only weak link left would be my water pump.
There are more than 5 parts to your cooling system. Many, many more possibilities exist.
Regardless of what Saab says, I am not really sure why they would have changed the function of the cooling system from both fans working together to just the one primary cooling fan for the latter years.
They didn't. The cars were always meant to work on one fan. The wiring and logic of the relays changed several times, but they never needed 2 fans, unless the A/C was operating.
They all varied a lot. My opinion is that if you're not losing coolant, you're not overheating. The coolant won't boil until about 120 C.
 

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Discussion Starter · #16 ·
You make some good points. I've checked and re-checked and I'm not losing any coolant. Maybe the smartest thing to do would be to restore my wiring to the way it was before the fan mod. Unless I've inadvertently done something else, it should function again as it did originally. I'm of the opinion that the guys who put in the 82 degree thermostats and thermoswitches, and then brag about their temperature gauge being "pegged in the middle" are either exaggerating or forcing their car to run cooler than it ought to. From what I've seen and read, the temperature gauge on a 900, when working with a correctly functioning cooling system, is dynamic. It's not going to necessarily hold steady like the idiot gauges on modern vehicles. I guess the moral of all this is if it isn't broken, don't try to fix it.
 

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on all my 40+ 900's I have owned the temp gauge has NEVER moved about except when a problem was occuring, eg HG gone and a rad had a hole in it, both causing water loss = excess temp
 

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Put it back the way it was. The cooling system doesn't need two fans unless you have AC on, or your rad is failing. Also two fans can flatten the battery if you're stuck in traffic and the charging system is not A1. Run an 89°C stat all year round. You don't need to change it with the seasons. (Yes, I do drive in the South of France and Italy and it stays the same). I run 89°C in my cars and the gauge sits bang in the middle all the time unless idling when it will rise to 5/8 gauge and the rad fan comes on. Just for reference; I've measured a few gauges and they read 80°C at the bottom, 90°C in the middle, and 100°C at the top. I've found very few variations on this. Bear in mind in the Saab pressurised cooling system the water will boil at 120°C, so top of the gauge (100°C) is a long way from this.
 

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Discussion Starter · #19 ·
I decided to wise up and get the original fan setup to work.

I started by replacing the modified relay in position J with the original Bosch relay. Still, only the AC fan would run. I tried a replacement cooling fan, but it still didn't work with either. Just to be sure, I got into the wiring harness and checked for any shorts or wiring problems from the splice, but everything looked fine. I even removed that extra spade from the splice on relay H and it made no difference. Physically, it's the same configuration, except the splice is still on (spade is taped off). Is it possible that the splice/spade is drawing enough power from the primary cooling fan that it's not working? There's no other explanation I can think of as to why it wouldn't work. To clarify, I tried the original relays in their stock positions and, for good measure, replacement and alternate relays to narrow down any suspects.
 

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If you rad sensor is had it the fan will not work as that completes the circuit join the two sensor wires together and fan should run with ign off
 
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