Electrical Fan Wiring...

Ok so I have a 1980 buick regal with a 350 chevy engine. I put an electric fan from a ford taurus which is a 2-speed (low-high) fan.

Now the issue I'm having is with the main power wire (direct from battery) where the fuse is located. I first used a 40amp cartridge fuse and that worked for about a year, recently that fuse when out. I replaced it with a more heavy duty cartridge fuse about 2 weeks later the wires leading to the fuse melted/burnt off competely.

I talked to a guy about it at an auto parts store he suggested I use a 40amp circuit breaker instead, so I took his advice and installed it. Well on the fans low speed(a/c off) it works perfect. On the fans high speed(a/c on) the breaker trips. From all my research my fan shouldn't be pulling anymore than 40amps at peak so that's where I'm at I'm lost and don't know what else to do. Could the motor be bad? Do I just need a higher amp breaker?

thanks for any advice or tips it will be greatly appreciated.

40 amps is about 480 to 500 watts (depending on system voltage variations). That's a hell of a big electrical draw for any one device on the car. Even high-load items like electric window defoggers and lighting systems do not draw that much.

Drawing that much power from an alternator for a long period of time may cause it to overheat and be damaged.

I think the fan or wiring is bad.

40 amps is about 480 to 500 watts (depending on system voltage variations). That's a hell of a big electrical draw for any one device on the car. Even high-load items like electric window defoggers and lighting systems do not draw that much.

Drawing that much power from an alternator for a long period of time may cause it to overheat and be damaged.

I think the fan or wiring is bad.

40amps is what the fan was rated at peak by the manuf. Now that's only at startup it lowers and levels around 25-30amp. I've checked all the wiring so I'm positive it's not that.

If the fan is bad how can I be sure? Is there a way to test that?

I'm guessing you don't have a DC current meter that can register better than 40 amps. If you do, that would be a good way to check to see if the problem is in the fan or the wiring.

Does the fan blade spin freely by hand, or does it seem to be dragging? Maybe there is a piece of grass or string wrapped around the shaft causing it to spin hard. Or maybe one of the bushings is dry causing the load to remain high rather than just at start up.

If the blade spins freely, then you can use a multimeter to test the DC resistance through the motor windings. If you see more than an ohm or two, you probably have a problem with the motor windings. If you see a dead short, then I wouldn't expect the motor to run on low speed, but it certainly would blow the fuse.

Does the wiring have an external current limiting resistor for the low speed or is it a three wire motor?

-Rod

40amps is what the fan was rated at peak by the manuf. Now that's only at startup it lowers and levels around 25-30amp. ?
That is still a heck of a lot of power, equal to SIX ordinary car headlights.

I'm quite sure it is far higher that it should be. If the wiring is good, then replace that fan. It's most likely not repairable anyways and, at worst is a fire hazard.

FWIW compare your fan's blade diameter and depth with those fans listed on this chart. It may give you a rough idea about the load your fan should be drawing.

http://www.flex-a-lite.com/auto/html/electric-fans.html

I'm guessing you don't have a DC current meter that can register better than 40 amps. If you do, that would be a good way to check to see if the problem is in the fan or the wiring.

Does the fan blade spin freely by hand, or does it seem to be dragging? Maybe there is a piece of grass or string wrapped around the shaft causing it to spin hard. Or maybe one of the bushings is dry causing the load to remain high rather than just at start up.

If the blade spins freely, then you can use a multimeter to test the DC resistance through the motor windings. If you see more than an ohm or two, you probably have a problem with the motor windings. If you see a dead short, then I wouldn't expect the motor to run on low speed, but it certainly would blow the fuse.

Does the wiring have an external current limiting resistor for the low speed or is it a three wire motor?

-Rod

It's a three wire motor. Now I talked to somebody today and they said it's possible I might need to install a resistor but does a three wire motor need one?

That is still a heck of a lot of power, equal to SIX ordinary car headlights.

I'm quite sure it is far higher that it should be. If the wiring is good, then replace that fan. It's most likely not repairable anyways and, at worst is a fire hazard.

FWIW compare your fan's blade diameter and depth with those fans listed on this chart. It may give you a rough idea about the load your fan should be drawing.

http://www.flex-a-lite.com/auto/html/electric-fans.html

It lines up fairly well with whats on that site 16-28amp. I'm not at all worried or concerned with the amps its pulling I've researched this a ton and I know that it stays at around 25-30amps on high speed. Just to double check the wiring with you here is the diagram I used to wire up my fan.

http://i72.photobucket.com/albums/i170/unstable70/DualSpeed-Fan-Diagram.png

That diagram should work, and you're correct, with a 3-wire motor you should not need a series resistor. The series resistor would be used to limit the current to the motor for the low speed, high speed would be a direct path anyway. You are not having problems on the low speed setting. If you installed a resistor, you would have two low speeds but no high speed.

Does the fuse/breaker open as soon as high speed is engaged, or might it be a few seconds after it starts up? Do you know what year Taurus the fan came from? I wonder if in normal operation the high speed would kick in after the low speed has already been running, reducing the current surge for the high speed. You are starting up the fan from a dead stop rather than spinning it up from half speed or so.

My recall is the OEM Taurus fan relay configuration consisted of three relays. One of those 3 may have been a motor brake though for safety reasons, but I have access to several Taurus wiring diagrams that I'd like to review. If I knew the exact application, that would help.

-Rod

That diagram should work, and you're correct, with a 3-wire motor you should not need a series resistor. The series resistor would be used to limit the current to the motor for the low speed, high speed would be a direct path anyway. You are not having problems on the low speed setting. If you installed a resistor, you would have two low speeds but no high speed.

Does the fuse/breaker open as soon as high speed is engaged, or might it be a few seconds after it starts up? Do you know what year Taurus the fan came from? I wonder if in normal operation the high speed would kick in after the low speed has already been running, reducing the current surge for the high speed. You are starting up the fan from a dead stop rather than spinning it up from half speed or so.

My recall is the OEM Taurus fan relay configuration consisted of three relays. One of those 3 may have been a motor brake though for safety reasons, but I have access to several Taurus wiring diagrams that I'd like to review. If I knew the exact application, that would help.

-Rod

The breaker always open as it's directly connected to the battery. I have low speed set to the temp sensor and it works perfectly all the time. I believe my fan came from a 1994 taurus. During the summer I always use the A/C so it straight kicks to high speed.

Do you think it would be better to set the high speed to a temp sensor also instead of the A/C?

It looks like, according to the 1994 factory service manual, you might have the operation backward of typical. Also, you should have either a couple of thermal switches or a temp sensor and logic that will provide two outputs for the low and high speeds.
----------------
The cooling fan system is controlled during vehicle operation by the Constant Control Relay Module (CCRM) and Powertrain Control Module (PCM) 12A650 which will energize the radiator electric motor under the following conditions:

l Radiator electric motor is turned on with reduced current for the 3.0L SHO and on at low speed for 3.0L, 3.2L SHO and 3.8L if:

a. Engine temperature is higher than normal. Radiator electric motor starts running at 102°C (215°F) and stops running at 99°C (210°F).

b. A/C clutch is engaged.

l Cooling fan will run at high speed if:

a. Engine temperature is higher than desirable and radiator electric motor has been operating at low speed. Radiator electric motor starts running at high speed at 110°C (230°F) and stops running at 107°C (224°F).
-----------------------

-Rod

It looks like, according to the 1994 factory service manual, you might have the operation backward of typical. Also, you should have either a couple of thermal switches or a temp sensor and logic that will provide two outputs for the low and high speeds.
----------------
The cooling fan system is controlled during vehicle operation by the Constant Control Relay Module (CCRM) and Powertrain Control Module (PCM) 12A650 which will energize the radiator electric motor under the following conditions:

l Radiator electric motor is turned on with reduced current for the 3.0L SHO and on at low speed for 3.0L, 3.2L SHO and 3.8L if:

a. Engine temperature is higher than normal. Radiator electric motor starts running at 102°C (215°F) and stops running at 99°C (210°F).

b. A/C clutch is engaged.

l Cooling fan will run at high speed if:

a. Engine temperature is higher than desirable and radiator electric motor has been operating at low speed. Radiator electric motor starts running at high speed at 110°C (230°F) and stops running at 107°C (224°F).
-----------------------

-Rod

Interesting, do you have any wiring diagrams that I could use to better wire this up? I mean obviously I can't use exact factory specs as it's not a factory application but something that will make this work correctly?

What you really need to duplicate the OEM functionality is a couple of thermal switches of differing temp ranges. I'm not sure how much hysteresis you would gain from the switch itself. You might also need to rig up an operational amplifier to give you the hysteresis. I'm not sure I'm willing to draw up such a circuit with the hysteresis loop. That function would normally be provided via the PCM.

The factory wiring diagram just shows a block for the Constant Control Relay Module (CCRM) and the PCM for the control portion of the circuit. The internals of the CCRM for the fan control is really just simple electro-mechanical relays, nothing special there, and not a whole lot different from your diagram. The magic comes from the two thermal switches and the PCM. And of course reversing where the thermal switch is versus the A/C clutch.

-Rod

What you really need to duplicate the OEM functionality is a couple of thermal switches of differing temp ranges. I'm not sure how much hysteresis you would gain from the switch itself. You might also need to rig up an operational amplifier to give you the hysteresis. I'm not sure I'm willing to draw up such a circuit with the hysteresis loop. That function would normally be provided via the PCM.

The factory wiring diagram just shows a block for the Constant Control Relay Module (CCRM) and the PCM for the control portion of the circuit. The internals of the CCRM for the fan control is really just simple electro-mechanical relays, nothing special there, and not a whole lot different from your diagram. The magic comes from the two thermal switches and the PCM. And of course reversing where the thermal switch is versus the A/C clutch.

-Rod

Ok so I'll just do that and see if it works better. Thanks for the help I appreciate it.