Saturn radiator fan

Tiny
MOPARDADDY
  • MEMBER
  • SATURN
Have a 1997 saturn sc2, I just replaced the radiator fan, when motor gets warm fan dont kick on it starts to overheat, if I unplug the block temp sensor she fires right up but now I lose my gauge reading and I get cluster lights flashing obviously. Relay is good, temp sensor in coolant resovoir is good, any where else I can look.
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Monday, March 5th, 2007 AT 10:47 AM

11 Replies

Tiny
JACK42
  • MEMBER
The one in the resevoir is a level sender. In the back of the head is 2 sensors, 1 is the coolant sensor and the other is the gauge/light sender. Have seen problems with both
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Tuesday, March 6th, 2007 AT 7:40 AM
Tiny
PEPPERMRJ
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As Jack stated the sensor in the coolant tank is a level switch.

SOHC and DOHC engines from 91 thru 95 have a 2 wire ECTS and a 1 wire sensor for the gauge.

98 thru 02 have a single 2 wire ECTS that handles all functions.

The coolant temp sensor controls the input for the fan, gauge, and has a good deal to due with the air fuel ratio. This in turn can present poor fuel mileage, high idle, and hard/no start conditions.

"if I unplug the block temp sensor she fires right up "

The original ECTS from Saturn had a composite tip (plastic). They were known to fail after a period of time. Mine lasted around 100,000 mile on my 96 SC2.

Replace it with an updated brass tip model from saturn. It might or might not solve the coolant fan issue but will be money well spent either way.

Pretty simple swap. Just like replacing a spark plug. Check the wire conector for corosion and clean or replace as needed.

Good luck and let us know. :)
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Sunday, March 11th, 2007 AT 9:04 PM
Tiny
MOPARDADDY
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Why does the fan come on if I unplug the cts harness from the sensor?Does the computer since trouble so it turns it on for a fail safe? Is it possible that if my pcm was bad or erased in some manner, that it wouldnt send the signal to turn on my fan on normal conditions, but it would if I took the sensor harness off the cts?What im asking is since it works when I take the harness off does that mean my pcm is ok?Also if my vss is bad would that keep my fan from coming on also if it were sending wrong signals to pcm, like if its was sending the same signals as if it were up to a certain speed shutting of the fan?Thx
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Monday, March 12th, 2007 AT 9:51 PM
Tiny
PEPPERMRJ
  • MEMBER
"why does the fan come on if I unplug the cts harness from the sensor?"

Good question. It should not. With the ECTS unplugged the pcm sees a -40f degree reading. Did you closely inspect the connector for the ECTS? When the plastic tip fails it cracks. Slight amounts of coolant leek thru into the connector.

I would think that it is possible that it is shorted internally. This would read full voltage to the pcm which would then turn the fan on. Plugging it in might be undoing the short.

Also double check the ground to the fan.

The pcm and only the pcm turns the fan on.

The fan should come on from the request for the AC after about 40 seconds or so.

The fan will also come on when the pcm is in a diagnostic mode.

The pcm turns the fan on when it reads over 220f from the ECTS.

The pcm has a learning mode that it goes thru every time the battery is disconnnected. It will take a little drive and idle time for things to get back to normal. Try disconnecting the battery and then see what happens.

The vss has no input to the pcm for the cooing fan.

G luck and let us know. :)
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Tuesday, March 13th, 2007 AT 3:00 PM
Tiny
MOPARDADDY
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Ok, I checked the fan ground it was good.I took the ects connector out and singled out the pcm ects send and return wires so they were not in contact with each other, I started it and fan still runs, I turned car off and then I turn key to on but I didnt start it and checked voltage to wires and I get 5 volts from one and 0 volts from the other as to what my book says is correct. Doesnt look like any type of short in the wires or connector. Could the a/c be giving me problems because it doesnt turn on the fan either when everything is connected like it supposed to.I wait 40 seconds and even more and it still does not turn on fan. Also I followed wires through the wire loom to check for shorts but none that I see, I want to check under the fuse box under the hood but ran out of daylight and I couldnt fiqure out how to get it up. Thx
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Tuesday, March 13th, 2007 AT 6:40 PM
Tiny
PEPPERMRJ
  • MEMBER
The computer turns the fan on.

The ects tells the computer when the temp reaches 220f. The ects recieves 5 volts and then returns voltage (up to 5) based on the coolant temp. When the ects is disconnected you should have to jumper it (send 5 volts to the pcm) to start the fan.

The ac tells the pcm to turn the cooling fan on also after it runs for about 40 seconds. It must be working. If the refrigerant is low it will not let the compressor kick in and the coolant fan will not come on.

Is the ses light lit?
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Wednesday, March 14th, 2007 AT 12:04 AM
Tiny
MOPARDADDY
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When I take the connector/sensor out of circuit there is no light on and fan is running, when I put it back on, together there is no light and fan is not running. When I leave sensor connected with one wire the 5 volts wire I get no fan and a warning light on my cluster.I think pcm may have problems what do you think?When I got car I did found higher amp fuses in some of the other sockets like horn, body ect. And they were blown, I think they may have shorted out pcm. If I new what numbers were the send and recieve on my pcm I could elliminate that part of the harness and make my own 2 wire harness and hook it up to the ects and see what happens.I did replace all fuses that were blown with the correct amperage and everything works correct except the horn, when I push it, she sounds like it is inside the car but not outside. Horn outside car dont make noise but something inside is buzzing. Thx again for the help
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Wednesday, March 14th, 2007 AT 9:51 AM
Tiny
PEPPERMRJ
  • MEMBER
Sorry I can't walk and chew gum. The horn will be a seperate issue.

Can you have the codes pulled. Some local parts houses will do this for free if you dont have a scan tool. P0117/P1114 (1996-97 models) or P1628 (1996-98 models) will tell the tale. A scan tool will also give real time temps.

Go back and double check the fan installation and hook up. I always go back and double check especially when a problem arises after I have changed anything.

Good hunting! Let us know. :)
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Wednesday, March 14th, 2007 AT 7:16 PM
Tiny
MOPARDADDY
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Ok I doubled checked everything, I even went to saturn and got a new oem connector and oem sensor. When the temp gauges gets just a hair over center between c/h on the cluster thats when she starts to spue water out of res. The funny thing is as you already no, fan dont come on when shes plugged in but does when shes unplugged. So I left it plugged in, stripped some of the wire so I could jump it and it comes on, so it looks like the sensor is not performing, but it is fine actually, both of the sensors I bought work fine.I checked them cool and hot with my meter. Also my cluster warning lights dont come on when im overheating.I scanned my pcm but no codes, do you think its a pcm problem or a short in the harness?
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Monday, March 19th, 2007 AT 6:19 PM
Tiny
PEPPERMRJ
  • MEMBER
You need to check for voltage at the pins/inputs to the pcm. With the ects disconnected the voltage being returned to the pcm should be 0. If not there is a short in the harness and the pcm is getting a false reading.

If the ects voltage is 0, check the voltage coming out of the pcm to the cooling fan relay. It should be 0. If not I would suspect it. If it is 0 there is a short supplying power to the relay.

Check your manual for the wiring diagram.

Good hunting. :)
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Wednesday, March 21st, 2007 AT 3:12 PM
Tiny
MOPARDADDY
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Well guys, I got it to run right finally. There was no short, no bad sensor, no bad pcm, no bad connector, ect.I overlooked something very important. The expansion tank cap!I was getting boil overs from a defective cap not holding the correct 15 psi needed for the correct coolant boiling point. My coolant was never getting hot enough to trigger that ects before it would boil over. It runs nice now! :D
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Thursday, March 22nd, 2007 AT 7:59 PM

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