jgkurz Posted March 6, 2003 Share Posted March 6, 2003 Hi all, I had a friend of mine give me new Volvo V70 electric fan that I adapted to fit my 77z. The fan actually has a Bosch part# and seems well designed. I ran wiring, relay and a fuse capable of 30amps. My problem is that I keep blowing fuses after the fan has only run for a few minutes. I've checked all conceivable reasons for this and can only surmise that the fan motor is drawing over 30amps. This seems extremely high. Aftermarket 16" electric fans draw at the most 10.5 amps. I know Volvo uses some type of two speed circuitry so maybe they use some type of resistor rather than supplying a full 12v. I'm just grasping at straws at this point. Other than the above problem the fan works well and has no rotating resistance or drag. Any ideas? Thanks, Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 6, 2003 Share Posted March 6, 2003 I wonder if there is a bad connection close to the fuse that could allow the heat produced by this bad connection to reach the fuse through conduction and weaken it. If it is drawing more than 30amps (barely it seems), then I think that a wire as big as 10awg would feel slightly warm. Is there any difference between a fast and slow-blow fuse as far as longevity? Quote Link to comment Share on other sites More sharing options...
jgkurz Posted March 7, 2003 Author Share Posted March 7, 2003 Thanks for the reply Terry, All connections were soldered and test OK. I also thought about getting a slow blow fuse, but the I figured that would only patch the real problem. I really don't want to use a fan that draws so much amperage. I can get a 16" 2950cfm perma-cool fan that only draws 9.8 amps. However, I still would like to make this Volvo setup work because the shroud fits so perfectly. I'm starting to think the motor is working correctly but is suppose to used with some type of ballast resistor. Later, Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 7, 2003 Share Posted March 7, 2003 Pete Paraska has often bragged that his 2 speed Mustang GT fan draws 35 amps at high speed. If you ran the relay and soldered the connections, then you have done about as well as you can do. I would try two things. First determine what size fuse Volvo used with these fans. Second try hooking an ampmeter up and measure the draw. Maybe you need a 35 or 40 amp circuit? You might try contacting Pete and see what he used in the way of fuses. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 7, 2003 Share Posted March 7, 2003 Last-ditch thing to do if all other options are exhausted is find a way to reduce the loading on the fan motor (i.e. reduce number of blades if it is a many bladed fan that passes more air than needed). I don't know if a DC motor power usage is effected by the shaft loading or not) I only say this because I read where the shroud is very important. I have used ballast resistors on my headlights (high/low power vs beam) and found a lot of heat had to be dissipated this way. I used a parallel/series bank of 3 ohm/40watt resistors. That allows for adjustability in the future. Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 7, 2003 Share Posted March 7, 2003 Terry, I agree - any resistor that has to deal with high current (10+ amps) is going to be hot! One thing to consider is this: If the actual blades of two different fans are the same, the one that moves more air (which is what is needed to cool a radiator) will mean proportionally more torque. And for two electric motors that have the same efficiency and voltage, the one that provides more torque will draw proportionally more current (amps). So bragging about a fan's amperage is not all bravado. As long as it's not a fan with inefficient blades and motor. The Mustang GT fan has efficient forward swept contoured fan blades. The motor is efficient as well. So a good amount of the power used by the 12Volt, 35 amps sent to the fan is used to move air. I imagine a new car like the Volvo V70 has an efficient fan and motor design as well. So I wouldn't be too surprised or upset if it DOES pull more than 30 amps. I would see about finding out what size wiring, fuses and relay the Volvo V70 uses for this circuit. I used 8 gage wire for most of the run to the relay and fan ground, and 10 gage for short lengths. The Mustang uses a 60 amp fuse on the fan wiring (I put it between my ground wire and the common on the fan). I also used a fusible link (12 gage) on the +12 volt source before the 8 gage to the relays. I used two 30 amp VF4 relays in series for the high speed, and one 30 amp VF4 relay on the low speed. Over kill maybe, but none of the wiring or relays get warm when the fan is on high. The VF4 is a common automotive relay, like you get in any autoparts store. Also, if your wiring is too small (12 gage or less) for a fan that pulls 30+ amps, it will become hot and also add resistance to the total circuit. This will make the fan run slower than it should, and not cool as well. It might also make the fan draw more current, since it'll be running at a lower applied voltage (across the fan). BTW, yes, the alternator does bear the brunt of the load when the fan comes on. At idle, when the fan comes on high speed, my idle goes down 100 rpm due to the load. But the fan doesn't run except for when the car is sitting or going down the road when it's over 95F or when I turn on the A/C. The rest of the time the electric fan is off and no load is being put on the alternator and engine. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.