i have a 94 e420 the temp hands is starting to go up when iam setting still the fan on the left does not come on but the one on the left does come on when the temp gets real high. i can spin the fan an it acts like it wants to work but it will not run any sugestions an could the thermal stat is going bad havent changed it out in 4 years. also would the o2 sensor make your car miss an give you the that raw gas smell from the tail pipe

Well I dont understand what exactly your saying but if your fan comes on at 105 degrees your fine. If you want your cooling system to act like new replace the thrmostat and get a new radiator.

I replaced my radiator last month and now my fans never come on because my car never hits 80.

i was trying to say that the one on the right will come on when temp gets high the left one will not i can push the one on the left it will act as if it wants to start but it will not i put a new radiator in about 2 years ago when the old one busted on me on the highway from a trip

If one fan is not spinning up it needs to be replaced. They run on the same power source, so if one is spinning, the other one should be too.

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Thats not exactly true. The driver side fan can come on independant of the passenger fan using the A/C as its high speed controls that fan. I would test the passenger fan by running voltage to it. The power source for both he is correct on. So if 1 works the other has power but low speed fans are controlled by the engine temp sensor. Try jumpering the 2 wire sensor on the intake area and see if the fan comes on if it does maybe your sensor is bad.