AC/ Electric fan woes

[Churchlady]

Drewlee77 wrote:

"What link is there between the O2 sensor and the Radiator Fan? Page 8W-12-12 (diagram of the junction block) clearly shows a "connection" between the o2 sensor relays and the radiator fan relays (and the AC clutch relays) but I don't understand why or what the link is...?? I have noticed a drop in MPG recently, could my o2 sensor be going bad and cause both these problems? Seems far-fetched to me...."
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I'm reviving this thread because it seems to be the only vaguely related one I can find in a half-hour of searching, mostly because of that one post by Drewlee. I've had a recent ~3 mpg. drop AFTER having a new 02 sensor/cat/muffler installed, & now what seems to be an electric fan problem.

Yesterday I drove about 15 miles on my way to church (outside temp ~75, no AC), stopped by our inn, left the car running for 3-4 minutes while I quickly unloaded 3 armfuls of stuff, noticed the sound of a loud fan running I'd never heard before--at least from the outside of the car--& cycling off & on again every 15-20 seconds. I got back in the car & looked at the temp gauge & it was no higher than dead center of the red zone.

I drove the 1 mile to church, then 15 miles back home--no more sound of fan running.

Drove the ~7 miles to Walmart an hour or so later--still no AC, outside temp prob. 80--& before I got out I decided to let it idle to see if the fan came on again & it almost immed. did: on ~15 seconds, off ~20 seconds, back on ~15 seconds,etc. Temp gauge stayed well w/in or even slightly below normal. I drove home, fan didn't come back on. When I got home I left the car idling & opened the hood, but after 4-5 minutes the fan had not come on again.

The car has not pushed past the red zone since I've had it, even on a very hot day last week when I had the car idling w/the AC running for a good 10-15 minutes while waiting for my son outside Sears.

I'm sure something else is needing to be replaced at 93000 miles. What's the most likely culprit?

 

[RichP]

From the FSM 'If the A/C compressor and clutch cycle more than 5 times in one minute the freon level is low', next time the electric fan starts cycling pop the hood and watch the compressor, look at the front of it, you should see the compressor clutch engage and release and it should by more or less synchronized with the electric fan.
The day after I drained mine and refilled it to specs it worked fine all day, in the afternoon right after I filled up I pulled out onto the main road and accelerated hard uphill to get up to speed and into traffic, the A/C started blowing normal outside air temp and stayed that way till I stopped for a refill on my travel mug 10 minutes later after shutting off the engine, on restart it worked fine.

 

[Churchlady]

Rich, I'm not sure you're addressing me, but if so I guess I didn't make it clear--when I said several times "no AC"-- that I didn't even turn the AC on all day, nor the defroster. It's just the fan cycling on & off when there would seem to be no reason for it to.

 

[RichP]

Rich, I'm not sure you're addressing me, but if so I guess I didn't make it clear--when I said several times "no AC"-- that I didn't even turn the AC on all day, nor the defroster. It's just the fan cycling on & off when there would seem to be no reason for it to.

As far as I know there are ONLY three things that will turn that electric fan on, first is A/C compressor in the A/C postion. Second is the Defroster position, that turns on the compressor to supply dry air out of the def vents. Third is the temp in the tstat housing temp sensor when it gets up to the 'turn it on the coolant is hot', other than that it should not come on at all..

 

[Churchlady]

Well, it has to be the third of those. And there's just no way that car was nearly as hot as it's been before & after last Sunday. Does a temp sensor ever send out false "hot" signals?