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Member
- Joined
- Nov 11, 2017
- Messages
- 9
- Vehicle Year
- 1992
- Transmission
- Automatic
Hey all, I recently completed the Volvo fan swap (https://www.therangerstation.com/tech_library/images/volvo_diagram.JPG) on my 1992 XLT 3.0. I installed the BMW 91⁰/99⁰ switch in a bung fitting in the upper radiator hose.
My problem is this: when driving the truck around, the fan will stay off until it gets up to temp. Then, the fan will kick on, but no matter how long it runs it never seems to shut off. The engine temp as read from the dash gauge stays low, between the N in "NORMAL" and the bottom range of the acceptable temp. I'm not so much worried about the truck getting hot as I am about the fan staying on all the time, which as I understand it's not supposed to do and will shorten the life of the fan.
My suspicion is that somehow the upper radiator hose never gets cool enough to turn the switch off after the thermostat opens- it's my understanding that the temp at which the switch "turns off" is some temp under 91⁰c, but I don't know the internals of the switch itself.
My plan of action is to get a new upper hose and install it, then cut my lower radiator hose where temps are ~20⁰F cooler and install the bung and switch there. My thinking there is that, not only will the truck run a little the warmer since the coolant temperature in the lower hose will be cooler compared to the upper and therefore not trip the fan switch until later, but the switch will trip more readily when the truck is stationery, aka the radiator doesn't cool as effectively when standing still since there's no "natural" air flow and thus the temp will come up faster and the fan will kick on, as it's designed to do.
My question is this- I've always read that the fan switch should be where the temp is likely to be hottest (i.e. right after the engine, water pump, etc.) but is there any compelling reason not to just put it in the bottom hose instead, where it might work better?
My problem is this: when driving the truck around, the fan will stay off until it gets up to temp. Then, the fan will kick on, but no matter how long it runs it never seems to shut off. The engine temp as read from the dash gauge stays low, between the N in "NORMAL" and the bottom range of the acceptable temp. I'm not so much worried about the truck getting hot as I am about the fan staying on all the time, which as I understand it's not supposed to do and will shorten the life of the fan.
My suspicion is that somehow the upper radiator hose never gets cool enough to turn the switch off after the thermostat opens- it's my understanding that the temp at which the switch "turns off" is some temp under 91⁰c, but I don't know the internals of the switch itself.
My plan of action is to get a new upper hose and install it, then cut my lower radiator hose where temps are ~20⁰F cooler and install the bung and switch there. My thinking there is that, not only will the truck run a little the warmer since the coolant temperature in the lower hose will be cooler compared to the upper and therefore not trip the fan switch until later, but the switch will trip more readily when the truck is stationery, aka the radiator doesn't cool as effectively when standing still since there's no "natural" air flow and thus the temp will come up faster and the fan will kick on, as it's designed to do.
My question is this- I've always read that the fan switch should be where the temp is likely to be hottest (i.e. right after the engine, water pump, etc.) but is there any compelling reason not to just put it in the bottom hose instead, where it might work better?
