Looking at just chucking the little volvo electric fan and replacing it with nice new Hayden Fan that I also have their adjustable thermostat...

So my question, can I do away with the little volvo thermostat that fits on the outside of the radiator (and is now bad)...some mount on the hose.

Just hardwire past where the stock thermo had been and wire the new units up per their instructions?
Or....does the volvo ECU need that temp signal?

My understanding is that the ECU temp reading is critical from the thermo. that is a pain to reach under the intake and in the block...

Its starting to be AC weather and want to get it right.

Dave
1987 760 2.3 Turbo wagon
getting better every week

Hello, I assume you're talking about the coolant temp sensor/switch that triggers the electric cooling fan.

I don't know what kind of engine or fuel injection ECU you have.

In my 91 740 turbo I have the B230FT engine with LH 2.4 ECU.

According to the volvo wiring book for my car, there is no input to the ECU from the thermal switch on the radiator.

It gets a signal from a coolant temp sensor on the block.

The coolant temp switch is only used to ground the relay which then completes the circuit from the ignition to the cooling fan.

So if your new fan doesn't need the thermal switch, I guess you don't either.