Water Temp Sending Unit Wire and Electric Fan Relay
Just mounted the electric fan and currently wiring up the relay. The relay kit contained replacement temp sensor/switch. The "Yellow" wire is to be routed from the relay to one of the male spades then from the other male spade to a 12v switched or constant source.
Here is my question....since this sensor/switch is different than my other one, can my water temp sending unit wire be connected to one of these spades for my water temp gauge??
You can't connect a gauge to that temperature switch. That switch is either on or off - for a gauge, the sender produces a variable resistance proportional to coolant temperature. Your switched +12V source goes to one terminal - when the temperature gets to the switch's setpoint, the switch closes and puts +12V to the yellow wire, which triggers the relay to start the fan. If you connected your gauge to it, your gauge would see an open circuit whenever the temperature was below the setpoint and it would peg full scale low. When the temperature rises and the switch closes, it would put +12V to the gauge which is NOT what you want since the gauge wire is normally a variable resistance to ground. You might damage the gauge if you did that.
To get your temperature gauge to work, you'll need another threaded hole into a coolant passage (you could drill and tap one yourself since the intake manifold probably only has one hole) so that you can install the gauge sending unit. Either that, or change your fan trigger to a thermocouple style trigger that mounts inside a radiator hose or in the fins of the radiator.
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Last edited by Greg'66 5.0; 07-07-2012 at 12:38 PM.
I did the same fan/switch you are doing. As Greg said, you will need another access to a coolant passage if you want both a temp gauge, and the relay. I couldn't tell by your pictures, but do you have a plug on the top of your thermostat housing? That is where I put in the temp. switch for the fan relay, and left my gauge sender in its' original place on the manifold.
Not the best picture, but you can just barely see it above the dizzy vacuum advance canister.
After hearing this info lol and knowing I don't feel comfortable drilling and tapping into my intake, I went to autozone and they carry a single stage fan control with a radiator probe switch. How do you all feel about those? They may not work as well as tapping into the intake with direct access to the coolant. What part of the radiator would you put the probe?
I went and bought a water neck from around a '71 302 that had the built in temp sensor location. This solved that problem. Once I got everything wired up I let the car get warm and saw the fan kick on, but the temp just kept rising and rising. I guess the fan was not big enough. Plus the water neck is now leaking. All that time spent.....
I fixed the leaks and bought a new 180* thermostat and drilled a tiny hole in the flange to prevent air pockets in the engine. I took it for a cruise and the fan kicked on when it was suppose to and cruised at around 185*. I came back and let it idle for about 5 minutes or so and the temp came up, but never over 205*. Its about 92* outside. I don't know what it would do if I let it idle longer than that, but most of the time it would never idle more than 5 minutes.
Should my expectations for an electric fan be to maintain the 185* range at idle or decrease the time it takes for the temp to rise?? 205* is not too bad and all in all it is better than my mechanical fan.
Everyone has told me that 230* is the dangerous range and like you said, under 220 is pretty good. One problem though, my carb starts stumbling at about 210 and I am not sure why. I have the spacer between it and the intake. My mechanic had it really hot and it died on him. He either had to let it sit or open the throttle up to get it to start.
Just FYI, I did end up installing a 16", 2500 cfm fan from Performance Cooling. I just wasn't quite happy with the cooling on the original 14" fan...was not keeping up after I let it idle for a while. I will let you know how this one works.
Addition: This fan works great. It was 108* out yesterday and I cruised around for a bit and the water temp got to 195* when cruising. This new switch turns on at 195* and shuts off at 185*. I came home and parked it in the driveway and let it idle for a while and I actually saw the temp gauge go down slightly. I am very happy with the new fan.
I had a question about my electric fan.....to clarify, I was not aware of the differences in the Champion fans offered because there were so many 16" ones available. I apparently bought this 16" Champion fan. It measures 3.5" thick. They offer a lower profile one apparently.
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