Fan relay

psychoSEAL · #1 (**permalink**) 11-25-2009, 02:06 PM

I currently have a SPAL fan relay/switch 185. Over the past 2 weeks when I have had the car out. It has blown two inline 30 amp fuses. It never did this before over the last year. Why now? What would do this? Thanks!

Ron61 · #2 (**permalink**) 11-25-2009, 02:35 PM

Several possibilities. One maybe the fan motor is starting to get harder to turn and is drawing to much current. See if the blades spin easily and if there is a place to oil the shaft on the fan motor. Also a possible short which you might track down with an ohm meter. Try bypassing the relay for short time and see if the fuses still blow.

Ron

Rick Parker · #3 (**permalink**) 11-25-2009, 02:54 PM

Is the fuse between the power source and the relay or between the relay and the fan motor? If before, could be bad relay or motor as Ron described, if it is after, look at the motor.

psychoSEAL · #4 (**permalink**) 11-25-2009, 03:26 PM

Rick, The fuse is between the relay and the toggle switch. The fuse and fuse holder are melted.

Blas · #5 (**permalink**) 11-25-2009, 06:51 PM

The power path to operate the fan should only go THRU the relay not the toggle switch. The toggle switch should ONLY activate the relay. If you have the actual power path for the fan going thru the toggle switch, and then on thru the relay to the fan, it's wired wrong. You say you have the fuse between a power supply and the toggle switch, so you would only be protecting the switch with it, not the fan with it. (if it was wired correctly)
The relays function is to prevent the large power user (the fan) power supply from traveling long distances and the fans large current from flowing thru the little toggle switch. You might also check that fan is turning in the correct direction and not fighting the natural air flow while driving. Hopefully I understand how you have it wired correct? Loose grounds or power can cause this type of overheating problem too. Loose connections = higher resistance = heat.

Rick Parker · #6 (**permalink**) 11-25-2009, 07:07 PM

Get the Volt/Ohm meter out, and start looking for 12 Volts & direct shorts; first within the wiring circuit from the toggle switch to the relay (remove the wire from the relay to fan). Power the circuit (switch on, with fuse replaced) and check the spade at the relay for 12 Volts. If this checks out ok, next focus on the wire run from the Relay to the fan (without connecting to the relay) disconnect from the fan itself while checking it for shorts to ground. Lastly check the Fan Motor. 30 amps is alot of current, for it to melt the fuseholder (Is the holder rated for 30 amps?) you have something drastically wrong that could cause a real electrical fire. You should be using 10 gauge wire on that circuit too.
Find the problem and verify how the circuit is wired and protected. Blas makes good points.

psychoSEAL · #7 (**permalink**) 11-25-2009, 09:19 PM

This is a SPAL 185 relay. It has been in the car for almost 2 years and no problems. I have it wired so I can manually turn on the fan if needed and it is also wired so it will kick on/off automatically when it reaches the required temps. I'll check the connections and start back tracking. Thanks guys for the info. I let you know what I find.

undy · #8 (**permalink**) 11-26-2009, 05:37 AM

Check your operating voltages (alternator output etc). If your voltage drops the amperage draw increases. This can be caused by resistances and poor alternator output.

Dave

RICK LAKE · #9 (**permalink**) 11-26-2009, 06:53 AM

psychoSEAL The problem could be the contacts inside the relay. Over time they are burnt from the ampage being passed through them. The more they get burnt the high the resistants. Since you have had this system working for 2 years, I will GUESS that the wiring is OK and no chaffing in this curcuit. What is the amp rating on the switch? As said before the fan motor may have a dead spot and takes too long to start to turn. This will blow the fuse. The fan motor needs about 50-60 amps when turned on for the first 1/4 second. It's normal and it's a ampage spike.This is all it takes to cook a fuse. The fuses you have are probable slow blow ones. It just takes too long on startup before blowing one. Good luck Rick L. ps any chance you know a Watson? from the teams?

psychoSEAL · #10 (**permalink**) 11-26-2009, 06:07 PM

The relay is rated at 40 amp while the fuse is 30 amp. I will replace the entire relay wiring and check the fan to see if it rotates freely. Thanks