Still a issue with my electric fan?

cherokee4fun · Jun 8, 2007

Got some great advice about my electric fan on my 1990 4L last week, and I found that when I shorted the leads to my radiator sensor the fan came on. So I went out a bought a new sensor from NAPA. I thought maybe I had a air pocket, but fluid came out when I pulled the old one out and put the new one in.

So when should it kick on the fan? Today, I drove it, went to a drive through, and watch the gauge go up above the half way mark, and no fan? I don't even remember when the thing use to kick on.......

Usually the thing sits between the quarter and the half way mark when I driving around and putting air through the radiator. Just wondering if I might have another issue, or just need a hotter day to test?

Thanks in advance:spin3:
Bob

8Mud · Jun 8, 2007

Mine usually kick in somewhere between mid gage and the red. Guesstulating maybe somewhere between 212 and 220 F.
Mine comes on later than I'd like. I wired a switch into the sensor leads and ran two wires up to the center console, to a switch. Extended idle or low speed operation, I turn the switch on before it gets hot.
Many ohm meters now on days have temperature scales and leads. People think you have to get the thermometer (or sensor lead) into the coolant flow to get a good reading, not so.
Clean the paint off, shine the metal, put a dab of heat conducting paste on the metal surface and push the probe tightly onto the metal. Copper is a good conductor, the lag between the surface temperature and the coolant flow temperature is short enough to be largely irrelevant (like seconds).
I've been testing the surface temperature of copper pipes, in chiller refer systems, for decades. You get a very near true temperature reading on the surface of copper, stainless or even steel. Whatever fluid is flowing through the system transfers it's heat quickly through the metal.
Put a piece of cardboard in front of the radiator, put your temperature probe next to the thermal switch on clean metal with some pressure. Better yet with a dab of heat conducting paste.

cherokee4fun · Jun 8, 2007

Thanks for the info. I was thinking about wiring a switch, but I thought if someone else drives it, they might not understand! IS there a way to wire the switch so that the sensor still will work in case a "new driver" is at the controls!

Bob

8Mud · Jun 8, 2007

cherokee4fun said:
Thanks for the info. I was thinking about wiring a switch, but I thought if someone else drives it, they might not understand! IS there a way to wire the switch so that the sensor still will work in case a "new driver" is at the controls!

Bob

You run two wires to the thermal switch (sensor) wires (and just solder them on there piggyback or use a 2 to 3 blind connector) and use the in cab switch to jump them or short them together. Just like jumping the sensor at the connector for a test. The fan works with either the senor or the switch (whichever turns on first) as long as the ignition is on.
I piggy back splice the wires next to the sensor connector. That is downstream of the diode pack and a safe place for a splice.
With the switch left on, the fan turns off with the ignition. Fairly idiot proof.

ParadiseXJ · Jun 8, 2007

I just did this last week, works great!!

http://www.olypen.com/craigh/auxfan.htm

Ecomike · Jun 9, 2007

On a good working cooling system, 87-90 years, the coolant sensor sensing the engine coolant temperature will read about 212 to 220 F before the electric fan comes on, but the coolant temperature on the cool side, exit, return side of the radiator will only read about 185 F when the switch triggers and turns on the electric radiator fan. There is about 35 F degrees of temperature difference between the two locations if the hardware is working properly.

Personally I like these new Infrared, non contact temperature sensors, $20 at Harbour Freight here in the US and they work faster, easier and in very tight unreachable, but visible spots. I have used both, and checked the IR units against other gauges and they are very accurate around the engines and radiators in the 50 to 240 F range.

8Mud said:
Mine usually kick in somewhere between mid gage and the red. Guesstulating maybe somewhere between 212 and 220 F.
Mine comes on later than I'd like. I wired a switch into the sensor leads and ran two wires up to the center console, to a switch. Extended idle or low speed operation, I turn the switch on before it gets hot.
Many ohm meters now on days have temperature scales and leads. People think you have to get the thermometer (or sensor lead) into the coolant flow to get a good reading, not so.
Clean the paint off, shine the metal, put a dab of heat conducting paste on the metal surface and push the probe tightly onto the metal. Copper is a good conductor, the lag between the surface temperature and the coolant flow temperature is short enough to be largely irrelevant (like seconds).
I've been testing the surface temperature of copper pipes, in chiller refer systems, for decades. You get a very near true temperature reading on the surface of copper, stainless or even steel. Whatever fluid is flowing through the system transfers it's heat quickly through the metal.
Put a piece of cardboard in front of the radiator, put your temperature probe next to the thermal switch on clean metal with some pressure. Better yet with a dab of heat conducting paste.

Still a issue with my electric fan?

cherokee4fun

NAXJA Forum User

8Mud

NAXJA Forum User

cherokee4fun

NAXJA Forum User

8Mud

NAXJA Forum User

ParadiseXJ

NAXJA Forum User

Ecomike

NAXJA# 2091

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