I'm thinking ac pressure switch or compressor.

 

so this is irregular? How does the fan/rpms usually function with normal ac use?

 

Mine does that often at idle. It kinda reduces AC a little but I can rev her out to 1k+ and get extra cold but usually never needed. I’ve had it like that for a long time but no clue what it’s all about really.


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Come to think of it, my Mazda does this too. Idle will drop slightly.

 

my 4cyl accord did that, i change the battery to the v6 accord battery( a little bit higher output battery) and it solved that problem, been driving with that bigger battery for 6 years and doing fine without any problem.

 

My next battery imma try a bigger one. Possible a AGM. My alternator doesn’t give much juice at 900 rpm. Barely 13v actually. But higher rpm it does good. Possible just high electrical load I suppose. But maybe someone has a better answer or can explain.


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when the ac is on, there's more load, and they max out the output of the alternator, and the battery is supposed to help out the alternator at those moment at low idle ( below 1k rpm) but because most 4cyl battery is pretty wimpy ( in case of my 06 accord 4cyl) it couldn't help out my alternator to provide the system with enough amp. so i went with the v6 version battery and it has enough juice to help out the alternator at low idle , once the car starts moving and the rpm increasing over 1k rpm, the alternator start providing more amp , enough juice for the system and it also start recharging the battery. in the case of switching to a bigger battery, u need to upgrade ur ground , positive, frame and transmission ground cables to more beefier cables to handle more amp going through them. don't switch to a too over the top battery, switch to a slightly bigger ( 500 amp to 650 amp) and u should be fine. if u switch to double the output then u need to upgrade ur alternator to a higher output alternator also to be able to keeping up with recharging the double size battery, cause the stock one would have to work twice as hard to keep up then burn out quickly.

 

I thought that the radiator fan was suppose to remain on as long as the a/c was on, as in energized.
The idle fluctuating isn't unusual but the fan shutting down is.

 

I thought that the radiator fan was suppose to remain on as long as the a/c was on, as in energized.
The idle fluctuating isn't unusual but the fan shutting down is.

the fan cycling on and off, how long it stayin on depend on the coolant temp, most car at 180-185 the fan will be on, then stop around 165, then go back on again at 185. and the coolant temp im mentioning is the one coming out from the rad at the bottom not from the top hose where the coolant is coming out from the engine and entering the rad.

 

Radiator fan will only be on while the compressor is engaged with the a/c on. As soon as the compressor shuts down the fan will also shut down (unless coolant temp is high enough to keep the fan on).

 

Another one here with the same thing. On idle it might kick off then few seconds later it'll kick on and rpm goes up, rinse and repeat, unless i rev up. Also my aftermarket led lights seem to flash in the cabin when this happens. Was thinking of pulling an alternator at the yard and doing a high output mod to double the output amps. There's also a mod involving a diode to bump up the charging voltage to 14.7-15V, but i suppose that's not a good idea.

 

The fan turns on and off with the cycling of the compressor. The computer raises idle rpms when the compressor cycles on because it puts a load on the engine and the compressor needs slight higher rpms to pump refrigerant. If you are feeling a vibration that could be a sign of worn out engine mounts.

 

Thank you all for chiming in. I do see the compressor activating along with the fan’s actuation. Should the compressor be kicking on and off so often? It seems to be as often as 10s on, 3s off, but it varies. 80+ and humid conditions here if that matters. If this behavior is not intended, what does it indicate isn’t operating correctly? Thanks again all.

 

Time to put of a/c gauges on it. Low refrigerant will do that but so will an obstruction raising the hi pressure side. It'll cycle to drop the pressure to protect the system. Has it ever been properly serviced?

 

Thanks for your reply. I bought the vehicle recently and have been fixing it up one thing at a time. I’ll have the AC serviced and report back.

 

After some testing, it appears this rapid (10-20s windows) cycling of the compressor and fan is directly related to the dashboard settings. The LO fan setting causes it. The RECIRC turned on also causes it, unless you are on HI, in which case it does not occur. Besides these two instances, the compressor and r fan stay on indefinitely while my AC is turned on. (All testing at idle)