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Fans Come On Right After Car Is Started....Why?

R

RubyDropTop

Guest
Hi guys -

Can't figure this out....why would my fans come on within 5 seconds of starting my car? The motor is ice cold and the A/C is OFF, so why would this happen? :confused
 
Which Fan

Or BOTH?

ANy ECM mods?


Vig!
 
Good Question...

All I know is that I hear at least one fan kick on right away (sorry, I'm not as mechanically inclined as some other members).

The system cycles as it should after that...fans coming on at the dreaded 228 degrees, dropping the temp to 217.

No mods to the ECM.

Any thoughts?
 
RubyDropTop,
Is it possible your hearing the Electric Air Pump that's part of the (A.I.R.) Emission System? It usually comes on with a cold engine.
The Air pump is located up in the Front Left Corner of the engine compartment and runs for a few min. on cold starts.
 
Pop the hood

Watch which fan comes on.

The relay is probably getting funky


Vig!
 
No, no check engine light is on.

Can you humor me...where would I find the relay for the fans? Thanks.
 
drivers side of the radiator housing, there are two of them mounted there (if the hood is closed, it will be between the headlight and the radiator, two small black boxes, with wires coming out of the bottom of them).... If only one fan is coming on, you can unplug them both and switch them... after the switch, if the other fan is the problem, then it is the relay.
 
Okay, I know exactly what you are talking about. :duh . I've looked at those 2 boxes so many times and wondered what they were.

Thanks for the guidance...greatly appreciated. :)
 
An afterthought - if I wanted to simply swap both of the relays out for brand new ones, is that a pretty simple task? Are they available from Mid-America, Eckler's, etc.?
 
probably the easiest thing you can do to your vette... just unplug them, unscrew them from the housing, and replace. Available through the big parts guys, ecklers, mid america etc. also should be able to get them through your chevy dealer... may even be cheaper through chevy since there is no shipping
 
One More Question...

Would a bad fan relay cause a code to be thrown? I don't have any codes, so I'm just wondering.
 
I don't think it has a code... I don't even think the car can tell the relay is bad... it just goes on its merry way in ignorant bliss:)
 
Okay, I was just wondering. It wouldn't hurt to change them out anyway. I'd be surprised if they were bad, but stranger things have happened.

Thanks for your help. :)
 
The ECM has NO WAY

To detect if the relays are ACTUALLY closing.

Typically the fan as it gets old draws more current.... and the contact points on the relay get pitted.. as they get worse the relay clicks on and draws an arc ( think spot welding) and it's JUST enough to keep the contacts together reguardless of what the coil of the relay is doing.



Vig!
 
Ruby,
Before you just go replacing the relays try the simple tests the guys have mentioned. If you hear the noise in the morning at startup after the car sits all night and is cold, then there is a good chance you're hearing Air Pump doing its thing. It is noisey. When I first got my92 I thought it was the fans kicking on. It wasn't. Wait a few minutes and it goes off after the engine warms up a bit. With the hood up look at your 2 fans. If they aren't turning you'll actually see the fan blades. If they're both turning you definetely won't and you should feel the air blowing up by the radiator. If it's just one running then try as suggested. Just turn the car off and swap the connections on the 2 relays. Start her up and see if it moves to the other fan. If it does scratch 1 relay. Replace them both if you feel better about that and keep the good one as a spare. Get the relays from the dealer. I've had better luck with the TRW relays from the dealer. I've tried Autozone and the relay brand I got didn't last long.
Graham
 

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