Saturn radiator fan

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

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. :)

"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. :)

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?

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. :)

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. :)