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Cooling Fan Switch Location/Update pg 2 post 13

496truck

496truck

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Getting ready to install an electric cooling fan. Have a couple options on where to locate the switch. This is a single wire grounding switch sourced from an 87 Camaro V8.

First option would be the port on top of the water pump. My thought on this is that the fan would cycle on/off too quickly. Cooling the fluid and hitting the switch as soon as it enters the pump.

Second option would be to put it in the Temp sensor location and put that in the water pump, it's close enough to reach. But this may always tell the computer it's running colder than it really is cause it's reading incoming coolant temp instead of at the t-stat.

I guess one more option would be to buy a water outlet with a threaded hole in it and put the switch in that.

I may have answered my own question but, discuss....
 
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Couple of thoughts.
First, I assume that this is going to be an auxiliary fan, not a replacement.
If so, then you want the sensor to measure what the fan is cooling. The fan is not going to cool the engine directly. Its going to cool the radiator. So, to measure the need for the fan, you are best off measuring the radiator temperature.
Plus, the water volume in the radiator is large enough to average out the temps.
Thus the fan will not be cycling on and off so much.

One might think it would be nice if the thermostat stuck and the engine was overheating, to have the fan come on. But it would serve no serious purpose.
Any small amount of increased airflow across the block would not be of much use in that case.

Most fans use a small two wire switch with a tab that slides in between the fins of the radiator. Perhaps with some heat sink compound to make a better thermal connection.
I know you already have a switch, but these are fairly cheap, and I think will do you a better job than trying to find a place in the block.

As for relocating the computer sensor, I recommend against it unless you want to explore the results.

Modifying sensors for better performance has a long history. Sometimes it works, sometimes it doesn't.
But, whenever you modify a sensor from factory, there is a period of experimentation to see if you made things better or worse.

In your case, you would not be doing it as an experiment, but that would be the result.
Unless you want to do the experiment, I suggest the sensor is better off left where it is.
The truck runs good where it is, no sense in inviting trouble.

You might also consider wiring a relay to the air conditioner compressor clutch wire to turn on the fan with the compressor.
A lot of cars have those. The fan comes on automatically when the air conditioner compressor does.
The theory being that the extra cooling will be needed anyway, so might as well get a jump on it.
 
Your 2nd option with a simple T is what I used, works perfect. I would not use a probe sensor, ditched mine due to poor results.
 
misc002-1.jpg


Keep it simple...
 
I like the "T" idea but wonder about bleeding the high spot. Suppose I could just loosen the sensor to let the air out.

Fordum, It could be considered a 'replacement' of sorts. I am 'replacing' the engine driven clutch fan with an electric fan from a Volvo. I've heard bad things about the fan switches that sit in the radiator fins (not working, falling out). I've heard bad things about the probe type that fits into the radiator hose (leaking). So, I wanted to go with a factory style switch that grounds at a set temp and completes the relay circuit. I was just curious to know if anyone had input on the different locations to put the sensor. You make a good point on the cooling system having enough volume to equalize or at least be within the same range from the water pump to the t-stat. Something I had not thought about.

Oh, and air conditioning? What is this 'air conditioning' you speak of?

:D
 
OK, got it now. I have used the radiator mount type switch, but I glued it in with hardening heat sink compound, so I didn't have a problem with it falling out.
But, it was an auxiliary fan, not as critical as yours will be.

I found this site. Know nothing about it, but he has some interesting information in the FAQ about mounting the fan.

http://www.the-fan-man.com/index.html
 
If this switch is the stock unit from that Camaro motor, you may not like it's 205 or so degree setting that it switches on at. I had an '89 IROC with the TPI350 and electric fans, it was always overheating in the Phoenix area, I got online through Jegs and bought a lower temp setting switch to turn the fans on alittle earlier and that helped out alot.
 
Fordum said:
OK, got it now. I have used the radiator mount type switch, but I glued it in with hardening heat sink compound, so I didn't have a problem with it falling out.
But, it was an auxiliary fan, not as critical as yours will be.

I found this site. Know nothing about it, but he has some interesting information in the FAQ about mounting the fan.

http://www.the-fan-man.com/index.html
Click to expand...

Thank you. I'll check that out.

4xcrazy said:
If this switch is the stock unit from that Camaro motor, you may not like it's 205 or so degree setting that it switches on at. I had an '89 IROC with the TPI350 and electric fans, it was always overheating in the Phoenix area, I got online through Jegs and bought a lower temp setting switch to turn the fans on alittle earlier and that helped out alot.
Click to expand...

Also good to know. I'm running a 195* t-stat so I wanted to have the matching fan switch. I actually have an old Hypertech fan switch for a 180* stat left over from the last Camaro I built. I ended up wiring that fan to run all the time with ign ON. Those fans do not pull enough air when sitting in traffic. Maybe I'll just go buy a 180* stat for this truck and run the switch I have already istead of buying a new stock temp switch. If I run the 180 switch with the 195 stat it could have the fan constantly running. They should be matched.

The fan I'm gonna run is a good size and pulls plenty of air. It's designed to pull enough air to cool a radiator, A/C condensor, and an intercooler in a confined space. All I'm trying to cool is a radiator and a trans cooler in a not so confined space. I don't need the fan constantly running, I'd like it to cycle on/off as the factory would have designed it.
 
Why not put the 205 switch in the head. The head will be 10° or more hotter than at the thermostat.
 
miniwally said:
Why not put the 205 switch in the head. The head will be 10° or more hotter than at the thermostat.
Click to expand...

Bottom line is, I didn't want to mess with that location. Can hardly see it and I don't think that plug was coming out of the head anyways. But, you are right, that is where the factory put the F-body switches.

Update:

I ended up putting the switch in the water pump port. This was the stock temp F-body switch. Did this last Wednesday night after work, installed the fan and all. Drove to work and back Thursday, kinda warm out, didn't sit in any stopped traffic, never had the fan come on. Took Friday off to pack the truck and drive 2.5 hrs out to western Mass for a wheeling/camping trip. IT WAS HOT OUT! Upper 90s and humid, hit a few stop and go traffic spots, watched the temp climb (note: not sure of the accuracy on the factory gauge), still never heard the fan come on. Temp always dropped back down to it's normal point on the gauge once I started moving again so I didn't worry about it till I got where I was going. Finally arrived, popped the hood and grounded the switch wire and let the fan run a few minutes with the hood open.

In good thinking ahead I made sure to bring my 180 fan switch with me and the old clutch fan just in case. Swapped it out in the morning with the 180 switch and wheeled all day with the fan cycling like it should and the temp gauge never climbing much more above where it normally sits (keeping in mind, the factory gauge sender is in it's factory position in the drivers side head). And it was still wicked freakin hot out. Idling, slow crawling, pushing it up obstacles it stayed cool through out the day.

So, at this point, I'm keeping the 180 switch in there. It seems to run at it's normal temp and operate properly not running too hot or cold from when the clutch fan was on there. The fan pulls enough air that when I was at the gas pump filling it up I could feel the warm air blowing on my legs all the way at the back of the truck. So far, so good. Any thoughts? Questions? Requests? Snide remarks? Insults? Sarcasm? General BS? Or a Fordum like story? :whistle:
 
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