This is a darlington transistor circuit and can fail open or short.
Diagnose engine cooling fan relay problem.
Installing a radiator core with too high density too many fins and tubes per inch can restrict air flow enough to create this problem.
But make sure to follow the instructions with the pressure tester as you can.
Home engine cooling fan and fan clutch fan and fan clutch if your dodge cummins radiator fan can stop while the engine is running it s likely the fan clutch has failed.
I m not sure if this problem was related to only getting heat through my cabin vents at high speeds freeway so i bypassed the heater core.
There must be an engine cooling fan of some type or it cannot sit at a stoplight.
Either a switched on electric one that has that job or a fluid filled fan clutch and fan on the waterpump.
Replace it with an oem clutch fan from mopar.
The symptom usually associated with a faulty fan read more.
Air must be flowing over the rad.
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I replaced the radiator.
There s a problem with the car s emissions system.
They both work fine.
If the radiator core itself is restricting air flow at road speed then maybe the only cure might be to recore it with a lower density core with more air flow area between the fins and tubes.
Identifying your particular vehicle its model designation its equipment and any bulletins is important.
Cooling fan relays fail when the radiator cooling fan no longer receives an electrical signal.
A broken fan relay means the radiator cannot cool down.
I checked the fan and fan relay.
If the fan motor does not work there will not be enough air movement through the radiator to dissipate the heat in the coolant.
A simple pressure tester will reveal the coolant leak.
May be bad water pump broken hose heater hose upper radiator lower radiator or a bad radiator itself.
Follow the instructions on the test of pressure to your cooling system also check for coolant leaks onto the ground from radiator area.
If your p1496 toyota estima check engine light is illuminated it s best to take it in for diagnostic testing which can feel like a hassle.
The coolant level remains full so no cracks or leaks in the resevoir tank.
Suggest that you rent a pressure tester from auto zone or advance auto and preform a pressure test on your cooling system.