The Aux. Fan Revisited (please)
 

I did a search, and I find things -- but not for the 123.

The fan that is front of the radiator (the electric one) on my car will not off. I turn the key, it goes on. The past week, it would go off when I turned the car off, now it does not go off unless I disconnect the battery.

I tried to follow the wire but it was dark, I'm sick as a dog, and I'm confused.

Can somebody please tell me what I can do to fix this?

Thanks a million

GD

You did not say exactly what model or year... but some of the 123's have TWO sensors , either of which can activate the fan relay. One is one of the switches on the air conditioner reciever/dryer and the other is on the block of the engine. It could also be that your relay itself is stuck/burned. That is all I know this time of the night....

Hi,

Sorry I didn't give more info.

1983 300TD (With a bad vacuum leak (could that have anything to do with it?)

Thanks,

GD

:D just didn't want this one to fall too low.

Thanks, GD

On that car I would guess it is hotwired. :o Just in case it isn't, look under the black plastic cover on top of the driver side fenderwell. There should be 2 or 3 shiny aluminum "ice cube" relays. Try pulling them out one at a time.

Rick! Happy to hear from you!

Last week the fan would always turn on when the key was turned on, and then it would turn off when the key was turned off.

Now, it simply does not turn off (with key out, etc.)

I'll go look for that ice-cube tray in a few minutes.

Thanks!!!

Very good chance also that if it has been doing this for some time you may have burnt or corroded brush holders under the fan. Mine were completely toasted as it appears that the fan stuck on and the PO never disconnected it. I tjust ran and ran until the brushholders literally melted away adn the brushes turned more or less sideways...

if you follow the main power wires coming off the fan they go down just under teh front air dam whcih is where there is a two pronged connector that the fan plugs in to. You can disconnect it there and then troubleshoot using a voltmeter to tell where it is in the circuit that the sensors have failed causing it to stay on all the time.

Ok,

Turns out on the driver side fender under the hood there is a black box with a cover that comes off when you squeeze the two parts of it. Under the cover there are 2 ice-cube size relays made of aluminum (I guess) the one on the right is the one that has the issue. When I give it a tap, it shuts off!

Now... Here's the next question.

Why does it turn ON as soon as I turn the key? Is it (a)the same relay? (b)the lack of vacuum???? (c) something else.

Thanks for the help! at least I'm half there!

:)

Ok,

Turns out on the driver side fender under the hood there is a black box with a cover that comes off when you squeeze the two parts of it. Under the cover there are 2 ice-cube size relays made of aluminum (I guess) the one on the right is the one that has the issue. When I give it a tap, it shuts off!

Now... Here's the next question.

Why does it turn ON as soon as I turn the key? Is it (a)the same relay? (b)the lack of vacuum???? (c) something else.

Thanks for the help! at least I'm half there!

:)

I believe the relay which is sticking on just needs to be replaced. If you are cheap like I am it just needs to have the high amp contacts smoothed/refaced. But check on the cost first as these are very common and you may find a generic one for around $5.

The relay allows a small current (the signal) to activate a electromagnetic switch to pass a much higher current to the fan. The contacts on the high current switch can become pitted and rough with use which creates a slightly longer lasting and more intense electric arc (when activated) than if they are smooth. This is causing the contacts to become "welded" together enough so the spring pressure of the relay cannot separate them when the signal current is shut off. Tapping on the outer shell is enough to break the weak weld and allows the contacts to separate...ending the high current to the fan.

These relays can often be taken apart carfully so you can see the problem. And a "points file" can then be used to file the contacts to a new sooth surface if you wish...but replacing the relay is probably best.

Dana