Electric Fan Thermo-switch location. Where?
06-02-2005, 10:32 PM
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Electric Fan Thermo-switch location. Where?
I replaced my stock fan with an electric aftermarket unit. The fan comes on between the last white mark and the red(on the right side). I placed the thermo switch in the upper right area of the radiator. Is there a better location like maybe a hotter area of the rad. Any suggestions would be greatly appreciated!
06-03-2005, 01:35 AM
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K -
When you say upper right of the radiator I'm guessing you are talking about where the upper radiator hose connects to the radiator on the upper passenger side? If so that should be the hottest spot of your radiator as that is the coolant inlet to the radiator. Do you have an oil cooler in your radiator? That is located on the drivers side of the radiator. The oil cooler will also add heat to the coolant just before it get pumped back into the engine. How many CFM is the fan you put in place of the factory one? I can't remember what the CFM number should be but I think around 3,000+. Maybe you need a second fan?
When you say upper right of the radiator I'm guessing you are talking about where the upper radiator hose connects to the radiator on the upper passenger side? If so that should be the hottest spot of your radiator as that is the coolant inlet to the radiator. Do you have an oil cooler in your radiator? That is located on the drivers side of the radiator. The oil cooler will also add heat to the coolant just before it get pumped back into the engine. How many CFM is the fan you put in place of the factory one? I can't remember what the CFM number should be but I think around 3,000+. Maybe you need a second fan?
06-03-2005, 01:39 AM
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That's about the hottest spot on the radiator. Mine behaved somewhat like that with the standard 95°C switch in the stock location, which is at the opposite(coolest) corner of the radiator. Maybe your thermostat is closing late, causing the water circulating in the block to get hotter than it should before the thermostat closes and sends hot water out to where your sensor is located...
In any event, before you panic, you need to know the true temp of the water as it relates to the various positions on the gauge. In my case the needle tip just touched the left edge of the red when the coolant was at 95°C. It's been said that 928 gauges couldn't tell you yesterday's weather... and I can't argue. There was a thread recently with lots of people describing their varying observations of the relationship between the gauge reading and reality. You can slip a thermocouple into the coolant where the top hose meets the water bridge, use an IR thermometer, etc.
In any event, before you panic, you need to know the true temp of the water as it relates to the various positions on the gauge. In my case the needle tip just touched the left edge of the red when the coolant was at 95°C. It's been said that 928 gauges couldn't tell you yesterday's weather... and I can't argue. There was a thread recently with lots of people describing their varying observations of the relationship between the gauge reading and reality. You can slip a thermocouple into the coolant where the top hose meets the water bridge, use an IR thermometer, etc.
06-16-2005, 01:49 AM
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IIRC the stock system includes a 95°C T-stat and 95°C fan switch in the radiator, so from that I'd say that it should run no hotter than 95°C. In reality though... 
there are also 75° Fan switches and thermostats available, and any car might have any combination of the above. There are a lot of differing opinions on this, sometimes hotly argued(though at what temp exactly, I can't say). With Coolant/water mix and a proper pressure cap the boiling point is much higher though, and that's really the most important thing... the coolant should not get hot enough to boil.
Also, IMHO, if it's hot enough that you notice a difference in oil pressure that's too hot.
And to reiterate... forget about what the dash gauge says. It's meaningless until you experiment and find out what it's reading compared to actual temp.
there are also 75° Fan switches and thermostats available, and any car might have any combination of the above. There are a lot of differing opinions on this, sometimes hotly argued(though at what temp exactly, I can't say). With Coolant/water mix and a proper pressure cap the boiling point is much higher though, and that's really the most important thing... the coolant should not get hot enough to boil. Also, IMHO, if it's hot enough that you notice a difference in oil pressure that's too hot.
And to reiterate... forget about what the dash gauge says. It's meaningless until you experiment and find out what it's reading compared to actual temp.
06-16-2005, 01:59 AM
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Thanks Dave
the point of my inquiry is to establish how well (or bad) my gauge is working, and if I really do have a problem. Gauge was normal for a long time, until the car sat for a month and now it goes VERY high pretty quickly, while the rubber hoses are around 100 degrees F, but THEN the hose temps JUMP VERY QUICKLY to 180 degrees and more... I will be replacing the T-stat, but also thinking the gauge is confusing matters to me and thought to use a thermocouple at the top passenger side of the radiator to record the temps corresponding to needle position and take it from there
the point of my inquiry is to establish how well (or bad) my gauge is working, and if I really do have a problem. Gauge was normal for a long time, until the car sat for a month and now it goes VERY high pretty quickly, while the rubber hoses are around 100 degrees F, but THEN the hose temps JUMP VERY QUICKLY to 180 degrees and more... I will be replacing the T-stat, but also thinking the gauge is confusing matters to me and thought to use a thermocouple at the top passenger side of the radiator to record the temps corresponding to needle position and take it from there
06-16-2005, 05:09 AM
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The problem with putting the thermocouple there is that you will see temp change very late in the game, after the water in the block is hot and thermostat has closed to shunt water out to the radiator. The dash gauge would start moving long before you see any action on the TC(thermocouple).
The ideal way to figure out what your gauge is telling you would be to remove the temp sender in the block and place it in a metal container(grounded to chassis electrical ground) with water half-covering the sender and the TC in the water, perhaps tie-wrapped to the sender. You don't want the water to short the TC or sender wire to each other or to ground! If you can rig this up and heat the water slowly you will be able to take notes of various dash gauge positions relative to measured temps.
Next, you can put the sender back and position the TC at other points of interest, such as the T-stat outlet to the radiator. Just loosen the clamp, shove the TC far enough in that it's in the coolant stream, and snug the hose back down. Now that you know what the dash gauge is telling you you can watch that and the TC readout at the same time to observe when the T-stat closes. My experience has been that while temp gauges behave very differently from one car to another, they do tend to be very repeatable on any given car. Meaning the gauge is not accurate, it is precise, if you follow.
You could put multiple TCs at various points and get a nifty multi-channel temp meter like Tony's or just switch a single-channel unit between the TCs. In any case, you might want to experiment with the coolant cap removed, as the coolant might leak past the TCs under pressure. I wouldn't recommend tightening the hoses too tight, since you may create a leak path if the TC digs into the hose too much.
HTH
The ideal way to figure out what your gauge is telling you would be to remove the temp sender in the block and place it in a metal container(grounded to chassis electrical ground) with water half-covering the sender and the TC in the water, perhaps tie-wrapped to the sender. You don't want the water to short the TC or sender wire to each other or to ground! If you can rig this up and heat the water slowly you will be able to take notes of various dash gauge positions relative to measured temps.
Next, you can put the sender back and position the TC at other points of interest, such as the T-stat outlet to the radiator. Just loosen the clamp, shove the TC far enough in that it's in the coolant stream, and snug the hose back down. Now that you know what the dash gauge is telling you you can watch that and the TC readout at the same time to observe when the T-stat closes. My experience has been that while temp gauges behave very differently from one car to another, they do tend to be very repeatable on any given car. Meaning the gauge is not accurate, it is precise, if you follow.
You could put multiple TCs at various points and get a nifty multi-channel temp meter like Tony's or just switch a single-channel unit between the TCs. In any case, you might want to experiment with the coolant cap removed, as the coolant might leak past the TCs under pressure. I wouldn't recommend tightening the hoses too tight, since you may create a leak path if the TC digs into the hose too much.
HTH
