Over Heated
 

I'm new here.
I have MCV20 series and it overheated, it appears if the thermos aren't working correctly. The ac will turn fan on but when turns off both fans will continue to turn. I measured the voltage when this happens as 6v. I'm stuck. Any pointers????
All the earths seem ok. I have had both fans going flat strap.
Both temp switches seem ok.

will asume its a V6

motor thermostatic fan sensor can be replaced
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air con fan works with air con system as a seperate

other normal checks after an over heat

moisture and oil mix in rocker cover cap
oil in coolant ..coolant on oil dip stick
runs rough at cold start
water pump internal run by timing belt
replace thermostat,
cap
check for soft hoses

Manual or automatic A/C system?

yes v6. manual. a/c.
yes has two fans. one temp controlled one a/c controlled. from any diagram I can find there is 3 relays in the system that join the two fans together.
no water in oil, no oil in water,
while driving appears ok, temp climbs when stationary at lights etc.

If the temp is rising at lights. Either the coolant system has diminished capacity or the fans are not coming on to draw more air through the radiator.

The coolant system should be able to compensate for decreases in radiator airflow to a point. Beyond this the fans are needed. If the temp is rising quickly at lights, the coolant system may be have issues.

A diminished coolant system can be caused by a failed thermostat, clogged radiator fins or radiator core, low coolant level.

The coolant temp switches are either on or off.

When the coolant temp switch on the engine closes both motors should rotate at slow speed.

When the coolant temp switch on the radiator (or A/C pressure switch) opens both fans should rotate at high speed.

Disconnect the wiring to the radiator temp switch, the fans should operate at high speed.

Until the problem is found, don't let the temp go into the red or a head gasket may fail.

The A/C will run if the blower is on and heater switches on the defrost position.

What does "flat strap" mean.

Where are you measuring the 6V at?

The fans can operate at low speed (in series electrical connection) or high speed (in parallel) mode.

Measuring the 6v from battery negative to fan positive.

Flat Strap, Full speed, High speed.

So the coolant temp switch on motor is a lower temp range than the switch in the radiator?
Engine Temp Switch Opens before Radiator Temp Switch?

Ok so fans can operate in SERIES, or switch to PARALLEL?

Thanks.

The radiator switch is set to 203F.

The engine switch at 194F.

The relays can change the fan operation between series (low speed) and parallel (high speed).