Replaced alternator and Mass Air Sensor, car runs perfect, and no check engine light. Battery and Brake light on, and no radiator fan on. How do I check switches/relays how do I replace?

Aaaauugh! That makes sense. I damaged the pigtail plastic connector when installing the new alternator. I replaced that connector. I will check the output. I disconnected the neg. cable to battery while running and car continued to run. But I will hook up tester to battery. It was stalling originally, which is why I replace MAF sensor, the old Alt. tested bad.

please don't do that again.you CAN NOT unhook the battery while the car is running on todays vehicles!you will or may have fried something already.that old school trick we did back in the 70's and early 80's is not for these vehicles with all these sensors and computers on these vehicles now.but anyways,do your checks,battery voltage with car off should be 12.6,(2.1 volts per cell),battery voltage with car running 13.5-15.0 volts DC.post results.

Will do - Thanks!

10-4.post findings.

I tested the Alternator and Battery, both tests passed and the Voltage output registered at 15.4. The radiator fans come on when the air conditioning is turned on. I haven't yet test driven the car, to see if they kick on when car gets hot. I'm afraid of overheating and damaging head gasket. I have a low voltage tester to check relays and fuses, but I can't for the life of me remember how to use it. My suspicion is that the cooling fan switch, fuse, or relay is bad, the one that would work in conjunction with the thermostat.