Reference voltage to radiator fan switch? '95 CX

WillTravel

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1995 CX 1.5L D15B8 - Just finished replacing the head gasket, and I did the mechanical timing and ignition timing.

My cooling fan won't come on. The fan comes on fine when I jump the connector. With the key on the voltage to the fan switch reads 12.3v, but I heard it's supposed to be 4.8v-5.0v. I do get continuity between the switch's two connection prongs when the temp gage is about half way between cold and hot. But that still doesn't turn the fan on. I put dielectric grease on the switch's two connection prongs but that didn't help. The upper and lower radiator hoses and the heater hose all get hot. I did bleed the system till a steady stream and no air came out. But the bleeding was on level ground not on an incline as recommended.
Any body have any ideas as to what could be wrong?
 

WillTravel

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At 210* F the fan switch was reading 3.4 ohms. The reference voltage to the switch with the engine running was 14.4 volts. The connector has seen better days. Could that be my problem?
 


nd4sped

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Another question, is this fan switch supposed to receive a full 14.4 volts of battery voltage?
Pretty sure power at the connecter should match the current battery voltage. The fan assembly should have a controller built in to help regulate the necessary amperage pull.

Verify by using the troubleshooting in the Honda Service manual [you can get it in my signature ;) ]
 


WillTravel

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Thanks for the link. The manual has little info about the fan switch. But it did show the switch is connected to fuse 33 under the hood and fuse 13 under the dash, as well as relay 35 under the hood. Also it shows a connection to pin A12 on the ECU. Still, no correct voltage is referenced.
 

nd4sped

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Thanks for the link. The manual has little info about the fan switch. But it did show the switch is connected to fuse 33 under the hood and fuse 13 under the dash, as well as relay 35 under the hood. Also it shows a connection to pin A12 on the ECU. Still, no correct voltage is referenced.
Then the voltage reference will be battery voltage.
 

WillTravel

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What will be the consequence if I install a manual switch at the dash board with two wires that simply by-passes the fan switch by jumping the connector by manually flipping a switch?
Will manual jumping lead to any component damage?
I'm tempted to do this, because the fan does comes on when ever I jump the fan switch connector.
And since the fan switch itself does have continuity when heated to about 207*F as it's supposed to but still refuses engage the fan I feel at a dead-end.
 

nd4sped

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There is a temperature sensor on the radiator that actually tells the fan to engage or not.

Also if you turn on the AC do both fans engage? They should as the Air Conditioning will force power to both fans. If one fan does not come on, then I would try applying 12v of power directly to the fan to test the fan operation. If the fan does not turn on with direct power then its a bad fan motor and needs replacement.

Ghetto rigging power directly with a switch is going to lead to an overheated engine. Also if you leave the fan on and it overcools the engine it can actually cause drivability issues as the ECU may switch to closed loop if coolant temp is not high enough. This will cause richer running conditions, reduced fuel economy, etc.
 

WillTravel

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No AC; this CX is a bare bones but sweet running D15B8. On this motor the radiator fan temp switch is on the thermostat, but the fan only turns on when I jump the temp switch connector. I tested every thing I know and every thing works including the temp switch and the ECT, but the fan still won't come on unless I jump the connector. Still I have a new connector and switch on the way, but I'm not optimistic that they'll solve the problem. That's why i'm thinking of ghetto rigging it.
 

WillTravel

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Are you sure there's a temp sensor on the radiator itself? I haven't seen it. I've only seen the power plug.
 

nd4sped

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Correction, not on the radiator. There is the Coolant Temperature ECT sensor is on the cylinder head below and to the right of the distributor.
Thermoswitch is what you are after that is on the thermostat housing. Thermoswitch is what tells the ECU to power on the radiator fan.

31651
 
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