Date: Mon, 02 Feb 1998 05:48:59 GMT From: Ywan Mason <ymasonnopsamsouth.net> Subject: Re: 92 900S
2.1L engines had a fan circuit modification that Saab thought twice about and returned to previous systems operation. On the stock 2.1 system, only one fan comes on when the fan sensor closes, where on the older and 2.0 systems, both of them did. If you jump the two wires together going to the fan sensor on the left upper side of the radiator, with the key on, both fans should run. If not, and the left fan is not getting current, you may need the update. It is outlined in PSI 3/92-0191. It consists of swapping the Bosch relay with a Cartier relay and running one wire to the new relay from the signal wire on an adjacent relay. There is also another modification, in PSI 02/93-0305, removing the time delay relay and replacing it with a standard relay. If you have a tall black relay in position G labeled time delay relay, swap it with a 8522310. No other modification is necessary for this one, on a 900. We use a 8817538 thermostat and a cooler fan sensor to bring the cooling fans in line with the thermostat operation. Result is keeping the gauge near the middle of its range. Our sensor closes at 87 degrees instead of the stock one's 92 degrees. Fans come on earlier preventing the occasional overshoot. They do not seem to run longer as the engine stays cooler with this setup, but not cool enough to mess with any emission or running situations. We do not see an increase in fan failures with the cooler sensor. Head gaskets and hoses live a lot longer. We change the thermostat as a maintenance item every 30K, or if the car has been overheated. Many places only change it when it fails and when it fails, it often takes things with it, things like the head gasket. Since the upper radiator hoses and the bypass hose at the rear of the head leading to the heater core carry the hottest coolant in the engine all the time, they are the most prone to failure. They should at least be checked every three years if not replaced. Often, these hoses can check good and blow out next week, if unsure of their age, replace them. For the $25-35 you will spend for the hoses, you get piece of mind and no unexpected leaks. Also on the 92, you might want to consider doing away with the black plastic valve in the heater hoses over the alternator. This was installed to prevent a loss of cabin heat at idle, a problem that does not exist with the factory (8817538) thermostat and the cooler fan sensor, at least in the cars I see here in NC. I have seen many of these valves fail by leaking or blocking all cabin heat. Older model cars heater hoses simplify the system and mount right in place with no modifications. Make sure the hose coming from the rear of the head, off the tube the 90 degree bypass hose attaches to, is routed to the bottom of the heater valve and the upper one off the heater valve goes to the back of the water pump. Switching these can cause heater problems, most commonly heat when the temp is switched to cool, check this before replacing a heater valve for heat you can't turn off. Ywan Mason
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