Radiator fan works opposite of what its supposed to

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xirdneh
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Radiator fan works opposite of what its supposed to

Post by xirdneh » Wed Jan 10, 2018 4:26 pm

Am working on a tercel and radiator fan comes on when engine is cold and turns off when engine is warm. Just the opposite of what it should do.
What could cause that?
Love those Tercell 4x4 wagons but they sure suffer from road noise.

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irowiki
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Re: Radiator fan works opposite of what its supposed to

Post by irowiki » Wed Jan 10, 2018 4:42 pm

What happens if you unplug the sensor on the radiator?
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xirdneh
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Location: seabeck, washington, USA

Re: Radiator fan works opposite of what its supposed to

Post by xirdneh » Wed Jan 10, 2018 6:17 pm

Fan runs when unplugged
Love those Tercell 4x4 wagons but they sure suffer from road noise.

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rer233
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Re: Radiator fan works opposite of what its supposed to

Post by rer233 » Wed Jan 10, 2018 7:57 pm

Does the fan run if you connect the two wires in the radiator temp sensor harness together? If not, you've got a bad temp sensor.
if it aint there, there's a good chance it won't break!
83 SR5 Silver/Blue (Snowmobile/work beater)-totaled but drivable
85 SR5 Blue
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Petros
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Re: Radiator fan works opposite of what its supposed to

Post by Petros » Wed Jan 10, 2018 11:51 pm

sounds like a bad sensor. strange problem, never seen that. it might be someone fit the wrong type of sensor in the Tercel from another car (thinking they work the same way). I have seen similar things like that.

You never know with a car this old. One time many decades ago we bought a 1948 willis wagon for $100 (I was 15 years old). It had had a number of owners that did various modifications and "custom" repairs on it. It was hard to know what was stock. It had a carter carb on it, with a strange home made extension/adapter that was so tall you could not install the air filter (an old oil bath unit) because it was too tall. We removed the adapter, but the carb would not fit on them. So we cut off the studs, drilled it and installed new studs in the right place to fit the carb. It did not occur to me that carb did not belong on that engine, and now we altered the manifold so only that kind of carb would fit. But at least we could run it with the air cleaner. Oddly it had no oil filter at all, complete mystery to us. one of my dad's friends had a yard full of old jeeps and willis wagons, we visited him to buy some missing parts and discovered where the oil filter should go. It is a separate assembly bolted on like an accessory, and uses hoses from a plug on the side of the engine, and drains it back into the oil pan through a side fitting. Someone just removed it and installed plugs in the fittings where the oil hoses attach. the guy sold us a oil filter assembly as well, fair price, he was a great help to my brother and I getting this hideous old wagon running. It was all because some cleaver former owner thought it would save him time/money/something to run the old engine without any filters on it. Fast way to need a rebuild.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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xirdneh
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Location: seabeck, washington, USA

Re: Radiator fan works opposite of what its supposed to

Post by xirdneh » Thu Jan 11, 2018 1:26 pm

My grandpa had a Willy's wagon when I was about 5-8 years old. Seemed to always have a lot of spider nests in it. I will not be able to test the wires for a few days. Meanwhile I met someone who was an electrical guy and asked what he thought. He said there was probably a relay switch somewhere that may have been swapped out with the wrong one. Always on vs always off. So I will check for that too.
Love those Tercell 4x4 wagons but they sure suffer from road noise.

kitchman
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Re: Radiator fan works opposite of what its supposed to

Post by kitchman » Fri Jan 12, 2018 7:09 pm

The fan relay in the engine fuse box is normally closed (N.C.). The temperature switch in the bottom of the radiator is also N.C., which supplies the ground to the fan relay when water temp. is not hot, energizing the fan relay and causing it to open preventing the fan motor from working. Conversely, when water temperature reaches the prescribed hot temperature, the temperature switch is rendered into a normally open (N.O.) state which interrupts the ground to the relay, causing the relay to return to its N.C. position, energizing the fan motor. So if the relay in this car is N.O. type, the water temperature switch, which as noted is N.C. will be supplying a ground to this incorrect relay causing it to close and powering the fan when water temperature is cold.

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xirdneh
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My tercel:: 87 tercel 4x4 wagon w/reringed engine, 83 tercel 4x4 wagon w/salvaged engine and 4.1 Diff's
Location: seabeck, washington, USA

Re: Radiator fan works opposite of what its supposed to

Post by xirdneh » Mon Jan 15, 2018 3:13 pm

The relay was OK
Found another bottom of radiator switch and hooked it up to the plug. That worked so it is a bad radiator switch
Love those Tercell 4x4 wagons but they sure suffer from road noise.

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xirdneh
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My tercel:: 87 tercel 4x4 wagon w/reringed engine, 83 tercel 4x4 wagon w/salvaged engine and 4.1 Diff's
Location: seabeck, washington, USA

Re: Radiator fan works opposite of what its supposed to

Post by xirdneh » Mon Jan 29, 2018 12:59 pm

it was probably not a bad switch but the wrong switch
the normal switch for these cars takes a 19mm wrench
this switch was about 22mm so maybe it was designed to work in an opposite manor
i have no idea where it came from but it was found in my bucket of switch type parts for these cars
Love those Tercell 4x4 wagons but they sure suffer from road noise.

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Petros
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Re: Radiator fan works opposite of what its supposed to

Post by Petros » Mon Jan 29, 2018 3:44 pm

the hazards of having spares of used parts from more than one vehicle. In my garage I have lots of toyota parts, honda parts, Mazda parts, and Suzuki parts in various cans, boxes and storage tubs. If I use one of my spares, and it is not exactly the same, I do not assume it is the same part. I also try and make a habit of throwing out bad parts, sensors, relays, etc right away so it does not end up getting mixed back in with my inventory of good used spare parts. that has happened more than a few times...
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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