Electric Fan Woes
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Senior User
Joined: Aug 2013
Posts: 159
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From: East Texas
Electric Fan Woes
1971 F250 Highboy with Champion 4 row radiator and dual fans. Have a relay that kicks each fan on at 165 or one fan when AC head pressure is detected.
Both fans start out strong, but one gradually gets slower to the point you cannot feel it drawing any air through, while the other one is still blowing strong. This happens after the engine is completely warmed up. Moved the ground wire, just to make sure I didn't have a bad ground issue. Tomorrow I will get my volt meter in line to see if there is a drop when warmed up.
Relays are wired to the back of the alternator to maximize voltage and grounded to a bare spot on the frame.
Alternator is charging and the battery is full. All connections are clean and paint free.
Any other ideas would be appreciated.
Both fans start out strong, but one gradually gets slower to the point you cannot feel it drawing any air through, while the other one is still blowing strong. This happens after the engine is completely warmed up. Moved the ground wire, just to make sure I didn't have a bad ground issue. Tomorrow I will get my volt meter in line to see if there is a drop when warmed up.
Relays are wired to the back of the alternator to maximize voltage and grounded to a bare spot on the frame.
Alternator is charging and the battery is full. All connections are clean and paint free.
Any other ideas would be appreciated.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
2 x with Hio you may be border line only as long as you keep your vehicle moving.
Or try setting the temp a little higher to come on. Or do the 3g 130 amp alternator conversions that would surly handle all your voltage needs..
Orich
Or try setting the temp a little higher to come on. Or do the 3g 130 amp alternator conversions that would surly handle all your voltage needs..
Orich
Elder User
Joined: Jan 2005
Posts: 561
Likes: 2
From: Willow River B.C.
You need to hook up a multimeter at the fans and observe the voltage, this will tell you wether its a fan issue or power supply issue. Once you know that then we can narrow down the issue easier.
Logistics Pro
Joined: Nov 2012
Posts: 4,308
Likes: 19
From: Las Vegas, NV
something else to try would be to swap which fan comes off which relay. If the other fan slows then you know it's not in the fan and is either voltage or wiring/relay related.
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Fleet Mechanic
Joined: May 2001
Posts: 1,396
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From: Cupertino
Zazoos, you said that you grounded to the frame.
Try this: When the fan slows at temperature, run a wire directly from the negative battery to the ground wire on the slowing fan. I could be wrong but my hunch is worth a try.
The proper grounding point for this high current stuff is the battery terminal.
Let us know what you find.
Try this: When the fan slows at temperature, run a wire directly from the negative battery to the ground wire on the slowing fan. I could be wrong but my hunch is worth a try.
The proper grounding point for this high current stuff is the battery terminal.
Let us know what you find.
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Lead Driver
Joined: Aug 2003
Posts: 7,592
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From: **** hole San Jose ca.
If you have a voltage meter put on the battery then start engine.
And monitor your battery output volts before and then when fans come on an see what your charging rate voltage is, then turn on your head lights. If the voltage drops under 13 volts then I'd say do the 3g upgrade.
orich
And monitor your battery output volts before and then when fans come on an see what your charging rate voltage is, then turn on your head lights. If the voltage drops under 13 volts then I'd say do the 3g upgrade.
orich
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Senior User
Joined: Aug 2013
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From: East Texas
Thanks for the help. I was suspecting the fan had a weak motor, so I replaced the fan. The reason for this thought is because it was showing 14 volts at the fan that would not blow hard and I even switched harness from the good fan to the bad and it still would not blow hard.
New Fan installed and exact same problem. Truck warms up and the driver side fan barely draws air through the radiator. Switched wires with passenger side fan that is blowing hard and the driver side continues to be weak.
I doubt I have gotten two bad fans.
Yes, my alternator is 60 amps, but you would think that when I switch the fan wiring harness the problem would switch to the other fan.
Also after switching the harness from the passenger fan to the driver fan I had to give the driver fan a push to get it spinning. Keep in mind the opposite wiring was spinning the passenger fan without any issue.
I am looking into the 3g upgrade now, but I am confounded about the harness switch not switching the problem to the other fan.
New Fan installed and exact same problem. Truck warms up and the driver side fan barely draws air through the radiator. Switched wires with passenger side fan that is blowing hard and the driver side continues to be weak.
I doubt I have gotten two bad fans.
Yes, my alternator is 60 amps, but you would think that when I switch the fan wiring harness the problem would switch to the other fan.
Also after switching the harness from the passenger fan to the driver fan I had to give the driver fan a push to get it spinning. Keep in mind the opposite wiring was spinning the passenger fan without any issue.
I am looking into the 3g upgrade now, but I am confounded about the harness switch not switching the problem to the other fan.
Elder User
Joined: Dec 2006
Posts: 881
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From: Sudbury, ONT.
Are you using the fans and wiring kit that came with your Champion Rad? If so, are you running your main power feed through the circuit breaker that came with the kit? I just finished getting mine all hooked up. Both fans would start and run for 4-5 seconds, then both would start slowing down. If I tried running one fan at a time, no problem. I put my volt meter across the terminals of the circuit breaker, and you could watch the voltage jumps/ drops while the circuit breaker quickly kicked off/on. I replaced the 30amp circuit breaker with a 30amp fuse and now both fans run no problem. I guess I got a defective circuit breaker with my kit.
Tuned
Joined: May 2010
Posts: 281
Likes: 9
From: Benton City, Wa
1. What happens if you run 12v directly to the driver fan?
2. Is there ANY chance the driver fan motor is binding in some manner?
With regards to #1, move the driver fan ground to the same ground as on the passenger fan and test. I can't help but think you have a bad ground on the driver fan. Double check/replace the ground wire ring terminal to make sure it has a good connection.
Dan
2. Is there ANY chance the driver fan motor is binding in some manner?
With regards to #1, move the driver fan ground to the same ground as on the passenger fan and test. I can't help but think you have a bad ground on the driver fan. Double check/replace the ground wire ring terminal to make sure it has a good connection.
Dan
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Senior User
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From: East Texas
Update
I ran power and ground to both fans direct from the battery with separate wires and warmed the truck up. The driver side fan started off strong but after 10 minutes of idling it had slowed way down while the passenger was still going strong. I even unhooked the passenger fan in order to give all the available amperage to the drivers fan, but no change. I'm assuming I have just gotten two bad fans in a row. Maybe a bad batch from the vendor.
Thanks for the help. I will let you know if another new fan helps.
I ran power and ground to both fans direct from the battery with separate wires and warmed the truck up. The driver side fan started off strong but after 10 minutes of idling it had slowed way down while the passenger was still going strong. I even unhooked the passenger fan in order to give all the available amperage to the drivers fan, but no change. I'm assuming I have just gotten two bad fans in a row. Maybe a bad batch from the vendor.
Thanks for the help. I will let you know if another new fan helps.