Fan Relay

Pacco · #1 (**permalink**) 08-15-2009, 06:17 AM

Can a bad fan relay switch be a problem with dragging your battery down? How can you tell if the relay is bad? I have noticed some changes.

Double Venom · #2 (**permalink**) 08-15-2009, 07:02 AM

Good question.
I'l be waiting for a more knowledgeable reply, but yes i think it can. Mostly because it may be hooked up wrong or the relay itself is staying on/sticking?
You can always check the output or feed line with a test light to see if there is constant voltage.
DV

DV

Ron61 · #3 (**permalink**) 08-15-2009, 07:09 AM

Possibly what DV said and if your relay is a plug in type try unplugging it and see if you still have a draw from the battery. If it was contacts sticking in the relay, there would be no draw unless they had power to them and then the fan should be running or trying to depending on the amount of juice getting through. The winding of the relay could have a short that would continually drain the battery, but then the relay normally wouldn't work correctly. Did this just start or has it been working for some time and just now started doing this? If it has worked before I kind of doubt a wiring error unless one of them has worked loose or has started shorting with a high resistance to some ground. I will be watching for the answer to this also as it is an interesting problem.

Ron

Pacco · #4 (**permalink**) 08-15-2009, 07:19 AM

It has a SPAL wiring set up with an in line fuse between the relay and the hot side of the starter solenoid. The type to kick on at 185*. Fuse is ok. Fan would stay on for 2 minutes originally. Over the past couple of weeks I have noticed it wants to stay on longer. That's why I question the relay and the effect on the battery.

Ron61 · #5 (**permalink**) 08-15-2009, 07:41 AM

Are you talking about after you shut the engine off and is there a timer for the 2 minutes? If you have some unusually hot weather that could be a reason the fan stays on a little longer. I had my fans wired through a toggle switch so I could manually turn them on and off if the automatic thermostat failed. Also sometimes after driving is hot weather, when I parked the car I would open the hood to let the hot air out quicker and turn the fans on for a minute or so. And that would draw the battery down some. But I did it with the toggle switch and watched so I never drew the battery to low.I also kept a battery tender hooked to it when it was setting for a day or so.

Ron

trularin · #6 (**permalink**) 08-15-2009, 08:47 AM

you should make sure that you actually have a relay and not a thermal circuit breaker.

The relay will be bigger with a minimum of four contacts, two that turn it on or off and two that supply voltage when on.

Okay, if you have a relay ( unless there is some problem with you wiring ) it is either on or off. The coil that turns it on, usually is the same resistance.

Given that, the sensor in the block tells the relay to either turn on or turn off.

From what you are saying, you could have a couple of problems that would cause this ( minus the relay coming apart inside ): 1 the connection to the block may not be as good as it used to be. The sensor may be using the threads as the ground connection. If oxidation increases the resistance, the turn on point will change. 2. The wire connection to the sensor may be loose or "not as good as it used to be".

Try these first.

Blas · #7 (**permalink**) 08-15-2009, 09:26 AM

Fan relays are dirt cheap. Just replace it and see it it fixes your problem...Is the car running warmer than usual? Loosing any antifreeze?