James

I just finished wiring in my new 140 amp alternator following MAD Electronics "New System" plan. The schematic shows a 14 gauge fusible link installed at the end of my battery charge wire that connects to the positive post at the starter soleniod for circuit protection. I'm just curious about 1 thing and that is once I turn the car off and the alternator stops providing the power for both of my Spal fans all of the power to run these fans (until the car cools down) is going to come through this fusible link and the 10 gauge charge wire.
Is this fusible link going to be able to handle this amount of current or am I going to have problems?

BigBlockk

What is the current draw of the two fans? Have you asked MAD about this? Maybe get one of the MAD junction blocks and run the power from it.

BigBlockk

Later.....

James

I have a junction point (from MAD) where the fans pull power from when the alternator is running so this is not the issue I'm wondering about. Its when the car is not running is what I'm curious about.
The information I have on the current draw for these fans is as follows:
At start up each fan pulls 25 amps.
Once running they pull 11 amps each.
The start up draw is not an issue because they are running off the alternator its when the motor is off and they are pulling the power from battery through the fusible link and 10 gauge charge wire is what I wondering about.

427V8

Well there is no need for the fans to run when the car is off.

A bad idea in my mind.

James

You ever hear an electric fan running in a new car after someone parks it on a hot day?
I thought that was one of the good ideas behind electric fans besides the cooling performance.
A motor always gets the hottest after you turn it off.
I keep only one of the fans running until the thermostatic switch turns it off once the motor has cooled down a little.
I have had a configuration like this on another car for years with great luck.

PhotoVette1

Get rid of that fusible link! Get a high amp self-resetting circuit breaker. It's what modern cars use and they're only $16.80.



WAYTEK

Garrett1972

The table of American Wire Gauge states that 10 gauge wire is rated for 25 amps. With 11 amps each running that totals 22, so your toward the high end, but not over. Now if the fans start up while the car is off, all bets are off.

68/70Vette

The wiring for my electrical fan is such that the fan becomes unpowered when the ignition is turned off. I imagine my version of this problem will be the following: lets say the engine is running, the engine is at nominal operating temperature, the fan is running. Now I turn off the engine and the engine and fan stops running with my wiring scheme. Now a miniute later, I switch the ignition on. Now the fan will come on with the large in-rush start up current, and since the engine(alternator) is not operating, it looks like I'll get a max current through the fusible link.

Shorting out the fusible link (actually paralleling it) with a heavy gauge wire will solve the problem. However, now the ammeter on my C3 will not work because it really is a voltmeter that reads voltage drop across the fusible link. This is a problem that I will have to try to solve.

AlwaysWave

The fans are cooling at the radiator. The fans get their on and off signal from the sensor in the engine right? When you turn off the ignition and the engine stops, you also turn off the water pump, so no hot coolant is cycling through the system. If the fans stay on with the engine off, you're not cooling the engine.

Cars have had mechanical fans for a hundred years with no ill affects by leaving the engine hot.

My Spals turn on together (if the sensor indicates) off the battery with the ignition without any overload problem. I have a 110 amp alternator.

James

I understand that and realize that the water pump is no longer flowing coolant through the block and the radiator once the engine is turned off but the fans are still moving air across the headers and the block which helps to cool the exhaust, cool the engine, and evacuate hot air that would normally be trapped under the hood without them running once the engine is turned off.