97 non vtec 4 cyl-- Had to replace condensor fan, the motor was bad, no probs, but now, the only time that the cooling fans will run is when the air cond is on. When air is on both fans will run, when air off neither will run even when car is running fully warmed up in the Missouri summer heat.

I have checked the 2 switches/sensors that I can see

1. On water outlet to top radiator hose, resistance stays at infinity whether hot or cold, connector has approx 13 volts across

2. Where lower radiator hose comes into back side of engine. Resistance stays at infinity whether hot or cold, approx 13 volts across connector, when I short the connector both fans will run.


I Believe that one of the sensors is a switch and one is a sender of some sort of temp sender. All help is appreciated.. Thanks

 

Welcome newbie!

The switch back at the thermostat (lower hose) is the one that switches the fans while engine is running. By jumpering that wire, you showed that all the rest of that circuit is OK.

When you idle (AC off) does the temperature guage stay reasonable, or does it overheat? It's almost reasonable that some amount of air moving around will provide enough cooling without the fan. You may have to block the radiator with some cardboard to get it hot. Normally, the gauge will rise to 1/2 or so before the fans switch on.

You COULD remove that switch & check it in a pot of boiling water.

The switch in the UPPER radiator hose nozzle will operate the fan after the engine is turned off. It has a different setpoint, and of course the different location. It has no authority over the fans while the engine is running.

There's 2 temperature sensors in the end of the head, below the distributor. The sender for the dashboard gauge has only one wire. The water-temperature sensor for the ECU has 2 wires.

Finally, since this isn't really gonna result in a big write-up instruction, I'll move it to General Tech which is a more appropriate location.