melting fuse in engine bay
01-21-2007, 02:01 PM
#1
Drifting
Thread Starter
melting fuse in engine bay
Dear All, (1985 US, AUTO, 32V, 5.0L)
I installed a puller fan behind the radiator and hooked it up to a relay that is powered off of the jump post terminal at the right front of the engine bay, the relay is switched from a switch that is in the passenger compartment. Everything works fine, mostly. Occasionally the fuse (it is a standard ATC type of fuse like the ones in our cars) casing will melt due to heat and cause the fan to stop working. The fuse is mounted inline to feed the power for the relay and the control voltage. My question is: Is there too much heat in the engine bay where the fuse is located and that heat along with the heat produced by the circuit is causing the plastic fuse casing to melt? Should I switch to an inline fuse made from ceramic or glass to prevent this?
The fuse, relay, fan, and associated circuitry is all rated for 30 amps. I am an electrical engineer and an electrician so I am familiar with all that is going on with the circuit. I just need to know if/why there is so much heat in the engine bay right there.
Thanks to all.
I installed a puller fan behind the radiator and hooked it up to a relay that is powered off of the jump post terminal at the right front of the engine bay, the relay is switched from a switch that is in the passenger compartment. Everything works fine, mostly. Occasionally the fuse (it is a standard ATC type of fuse like the ones in our cars) casing will melt due to heat and cause the fan to stop working. The fuse is mounted inline to feed the power for the relay and the control voltage. My question is: Is there too much heat in the engine bay where the fuse is located and that heat along with the heat produced by the circuit is causing the plastic fuse casing to melt? Should I switch to an inline fuse made from ceramic or glass to prevent this?
The fuse, relay, fan, and associated circuitry is all rated for 30 amps. I am an electrical engineer and an electrician so I am familiar with all that is going on with the circuit. I just need to know if/why there is so much heat in the engine bay right there.
Thanks to all.
Last edited by RngTrtl; 01-21-2007 at 03:10 PM.
01-21-2007, 05:10 PM
#2
Nordschleife Master
Some fans have a huge start up current draw, even though its pretty hot under the hood, unless other stuff is melting I suspect the heating is electrical in nature. Somebody else just posted a thread about melting and it was the contacts IIRC making a poor connection.
OTOH I can picture many automotive products aren't "ul approved" if you get my drift, the 30 amp fuse holder that prays it never sees 31 amps.
OTOH I can picture many automotive products aren't "ul approved" if you get my drift, the 30 amp fuse holder that prays it never sees 31 amps.
01-21-2007, 05:30 PM
#3
What is the rated capacity, in ampheres, of the fan?
How many ampheres does the fan draw?
How long are the wires from the positive feed to the fan?
What are the cross sectional areas of the wires in the new circuit?
Once these factors are known then it can be determined whether the capacity of the circuit is suitable.
The fuse holder should not melt due to the engine compartment heat.
Tails 1990 928S4 Auto
How many ampheres does the fan draw?
How long are the wires from the positive feed to the fan?
What are the cross sectional areas of the wires in the new circuit?
Once these factors are known then it can be determined whether the capacity of the circuit is suitable.
The fuse holder should not melt due to the engine compartment heat.
Tails 1990 928S4 Auto
01-21-2007, 05:54 PM
#4
Nordschleife Master
Some nominal 30 amp fans draw 100 amps briefly when starting, its part of why I decided to use a PWM controller with a soft start function. www.dccontrol.com
01-21-2007, 09:31 PM
#5
Drifting
Thread Starter
the fuse holder is fine, it is the actual green plastic of the fuse that is melting and causing the failure. the wire gauge and all ampacities are fine of all connected equipment are fine. I just cant see so heat being generated in that area to melt the plastic of the fuse...I am still kind of baffled by this.
01-26-2007, 11:17 PM
#7
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
RngTrtl,
Usually these symptoms imply contact resistance on the blade terminals. Its not the fuse itself because it would just blow... so the high current is heating the blades directly due to resistance betwen the blade & fuseholder terminals - you need a cleaner (maybe) and probably better fuseholder.
The fuses are actually not the problem. You may do better getting a different type of fuse/fuseholder - at least look for one with heavier duty connectors. Although ATC fuses go up to typically 30A (and are available above) most ATC fuseholders are not good for this much. Even the ones on the CE panel are a bit dodgy at 30A (hence the issues with the main fan fuses on CE).
You can get high amp bolt down fuses or instead what I'd actually recommend is just to go with Maxi fuses (like bigger size ATC fuses), with a larger contact area the fuseholders are more robust - which is the big win.
Alan
Usually these symptoms imply contact resistance on the blade terminals. Its not the fuse itself because it would just blow... so the high current is heating the blades directly due to resistance betwen the blade & fuseholder terminals - you need a cleaner (maybe) and probably better fuseholder.
The fuses are actually not the problem. You may do better getting a different type of fuse/fuseholder - at least look for one with heavier duty connectors. Although ATC fuses go up to typically 30A (and are available above) most ATC fuseholders are not good for this much. Even the ones on the CE panel are a bit dodgy at 30A (hence the issues with the main fan fuses on CE).
You can get high amp bolt down fuses or instead what I'd actually recommend is just to go with Maxi fuses (like bigger size ATC fuses), with a larger contact area the fuseholders are more robust - which is the big win.
Alan
Last edited by Alan; 01-26-2007 at 11:57 PM.
