Wiring question!

I typically use a big puller elec fan on my cars because of the Texas heat & traffic. My cars will sit in 100 degree traffic for hours & never overheat but... I have a problem with the controller for the fan on my Nova. This is the 2nd time it has melted the fuse holder. I'm good at wiring but my knowledge of electricity is probably lacking. The wires coming off the controller are pretty big & the wires to the fan not so big. I'm wondering if that's the problem or should I also use a larger ground wire. This setup cuts on at 190 degrees & lasted for about a year. Any input would be appreciated!

BoB

Looks like a relay in the pic you showed. Is that also running your fan circuit? I would go with matching guage wire to ground and make sure the ground is also good. You can check that with a volt/ohm meter set on ohms. You should touch one lead of the meter to a part of bare wire going to ground and put the other lead right on the metal your are using for ground. Meter should read 0 ohms. If the relay in the pic goes elsewhere, I would wire one into your fan circuit.

smallfoot said:

Looks like a relay in the pic you showed. Is that also running your fan circuit? I would go with matching guage wire to ground and make sure the ground is also good. You can check that with a volt/ohm meter set on ohms. You should touch one lead of the meter to a part of bare wire going to ground and put the other lead right on the metal your are using for ground. Meter should read 0 ohms. If the relay in the pic goes elsewhere, I would wire one into your fan circuit.

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SF,
Yes... the relay is hooked up to the water probe to control the fan. I bought a new covered fuse box & will bump up the ground & check to make sure it's good... thanks!

BoB

I've had a couple of those go bad on my Vette. About a year seems about right-Chinese parts probably. If I ever get to a pull a part, I'm going to look for a fan controller off of a Volvo, they are supposed to be about the best ones out there.

Bamamav said:

I've had a couple of those go bad on my Vette. About a year seems about right-Chinese parts probably. If I ever get to a pull a part, I'm going to look for a fan controller off of a Volvo, they are supposed to be about the best ones out there.

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Bama,
Thanks for that tip. There's a great pick-a-part in Austin & I'll see if I can find one. There used to be some killer junk yards up in this area but the state decided they were eyesores & nearly wiped them completely out! Stupid thing was... most of the really good ones were out in the boonies not bothering anybody! Politicans!!!

BoB

There could have been some resistance from a marginal connection in the thing that melted.
corrosion even a microscopic layer is a bugger. ever buy a brand new LED flashlight and a while later it cuts out on you and you have to jiggle it? scotchbrite on the battery ends and connection fixes that

Electricity on the schematics goes from positive to negative but the electrons themselves flow from negative to positive as electrons have a negative charge. the body ground is your bank of surplus electrons which flow from ground to positive.

Torch said:

There could have been some resistance from a marginal connection in the thing that melted.
corrosion even a microscopic layer is a bugger. ever buy a brand new LED flashlight and a while later it cuts out on you and you have to jiggle it? scotchbrite on the battery ends and connection fixes that

Electricity on the schematics goes from positive to negative but the electrons themselves flow from negative to positive as electrons have a negative charge. the body ground is your bank of surplus electrons which flow from ground to positive.

Click to expand...

Agreed. If just the fuse holder melted it was probably due to a poor connection causing high resistance resulting in increased heat. If it was due to wire size being too small the wire itself would have over heated and melt the insulation and possibly also the wire.

I found the culprit! Appears the controller isn't working properly & the fan is running all the time! Mufflers are so loud I couldn't hear it when I go back & forth to Houston so I'm gonna try & adjust it or will slap a new one in there! Like Roseanne Roseannadanna always said... "it's always something"! [ddd[ddd[ddd

BoB

I've never had any luck with controllers, Bob, so I just run a switch and keep checking my gauge so I can turn it on when needed. We have tried Painless and a few other brands and they all fail sooner or later.

Don

donsrods said:

I've never had any luck with controllers, Bob, so I just run a switch and keep checking my gauge so I can turn it on when needed. We have tried Painless and a few other brands and they all fail sooner or later.

Don

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After a closer look... no controller just a relay so once the motor warms up the fan stays on & the fuse got overheated & melted. I have a Derale controller on my pickup but don't put as many miles on it as I do on the Nova. Probably gonna throw one of those controllers on there & if it melts again I'll go the switch route!

BoB

i run mine on a toggle switch, but also through a fuse that cuts off when key is off. i can never remember to turn them on and off most of the time.

I've had good luck with a temp sensor in the manifold or head. It actuates a 30 amp relay with 10 ga wire from the battery to the fan.
Jeg's $38.99 with free shipping

http://www.jegs.com/i/JEGS/555/1056...9&cadevice=c&gclid=CNSm996Cx8gCFQIOaQodu24Ljg

You can put a toggle in line for a backup too.

Here is the thing, no matter how long the fan is running you should NEVER have a wiring failure like that. In the event that the fan shorts or pulls more power than it should, the fuse should blow. You should be likely running a 40amp rated relay, and a 30 amp fuse and appropriately sized wiring for that size. The controller unit should only control the relay, not run the fan directly.

kenny c said:

Agreed. If just the fuse holder melted it was probably due to a poor connection causing high resistance resulting in increased heat. If it was due to wire size being too small the wire itself would have over heated and melt the insulation and possibly also the wire.

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This! I have found some of those blade type fuse-holders cause a lot of heat as they don't have very tight connections. The fuse needs to be a good tight fit in the holder, and clean, or you'll feel it get hot if you hold your fingers on it.

Some of the aftermarket box type fuse holders also get very hot, as they are cheap and nasty manufacturing.

bear with me, this can be a bit weighty..

in a system with components that are properly sized, the total voltage drop of a system is equal to the sum of all voltage drops.

a voltage drop is usually found in the resistance of a connection. so if you have a fuse holder, a relay, and a fan, that is a lot of places for resistance. when power gets to the fan, the fan motor requires a specific wattage to turn, which is the multiple of voltage and current, if the voltage is lower than it needs, the current will be higher to make the same wattage.

resistance in a high current connection will also produce a fair amount of heat. this is likely what is melting the fuse holder.

make sure your fuse holder is rated for the continuous current draw of the fan. for a 40A circuit that should be a minimum of 10ga wire, and 40A ATC fuses are hard to find so might want to go to a MAXI type.

like dirtyrat says, make sure your relay is also rated for the continuous current, some relays that say 40A are actually 20/40, meaning their continuous rating is only 20A, for the reason explained above, the resistance with the higher current will generate heat and fail.

make sure you have great connections and seal them with tape or use weatherproof connections to keep corrosion from damaging the connection and causing a larger voltage drop.

I just bought a flexalite variable speed controller from summit, it has an adjustable "on" temp and only spins the fan as fast as it needs to. I uses a solid state relay so it is capable of running more than one fan. It wasnt the least expensive thing, but boy does it work well. With a 16" spal puller, it only runs at an extended stoplight stop.

good luck!