2001 cooling fan amp draw? - JeepForum.com

 
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post #1 of 9 Old 09-14-2013, 11:09 AM Thread Starter
mar-tay1
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2001 cooling fan amp draw?

helping a friend with his wifes 2001 grand cherokee. the fan relay smoked and has been replaced twice so I checked the amp draw of the aftermarket fan and it's pulling 19 amps solid. Seems like too much, really arcs when you jump it, what amp draw should it have? Is there a way to bypass the relay so that the check enjgine light doesn"t come on? Thanks!

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post #2 of 9 Old 09-14-2013, 03:11 PM
Jaspah
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Quote:
Originally Posted by mar-tay1 View Post
helping a friend with his wifes 2001 grand cherokee. the fan relay smoked and has been replaced twice so I checked the amp draw of the aftermarket fan and it's pulling 19 amps solid. Seems like too much, really arcs when you jump it, what amp draw should it have? Is there a way to bypass the relay so that the check enjgine light doesn"t come on? Thanks!
Honestly sounds like the fan itself is going bad. The reason the fan relays burn out so quickly on the OEM electrical fan is that the fan is taking too much amperage to spin.
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post #3 of 9 Old 09-14-2013, 04:14 PM
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post #4 of 9 Old 09-14-2013, 04:44 PM Thread Starter
mar-tay1
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Thats what I was thinking, looks like too many amps through the relay. Problem is, it is a new fan. I purchased another relay and am a little hesitant to put it in.
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post #5 of 9 Old 09-14-2013, 09:16 PM
greeky510
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How did you test for the amp draw?

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post #6 of 9 Old 09-15-2013, 07:45 AM
Cobra Jeep
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I recently bought a snap on multimeter and bought the amp clamp to go with it. It simply plugs into the multimeter and then it has a clamp you put around the wire (kinda like a timing light) and will measure the amps running through the wire.
I was playing with it and decided to test the fan on my 99 WJ. It showed 22 amps while running. The fuse/relay box under the hood has a 40 amp fuse for the fan, so I figure mines fine. The relay is good too.

'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, home made front hub conversion, hydroboost. Warn M10000 winch. Currently building a stroker.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
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post #7 of 9 Old 09-16-2013, 10:02 AM Thread Starter
mar-tay1
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thanks cobra jeep that's what I was looking for. My Fluke meter shows about 19 amps or so while running, so I'm in the ballpark. I'm going to mount a separate relay,where you can get to it, so all the load goes through that rather than the factory relay, that way if there is a problem it will be simple to jump the fan if need be, and if it smokes, it's 5 dollars. THANKS AGAIN!
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post #8 of 9 Old 09-16-2013, 11:39 AM
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Just a few words about substituting a standard relay for the stock relay.

The stock relay (a pulse-width modulated relay) is a solid state device, not at all like a standard electromechanical relay. A signal from the PCM (a pulsating 5V signal) switches on/off the current through the relay; it does not energize a coil to open or close a set of contacts. The variable pulse-width of the signals sent from the PCM allows the fan speed to vary according coolant temperature. It's doubtful that a standard electromechanical relay can operate on the 5V pulse-width signal, and if it could, the frequent opening and closing of the contacts would probably cause them to degrade quickly. If the PCM signal is not or can not be used, you can count on a code being thrown.

Some people have had success mounting the stock relay on a heat sink in an area with good air flow. You might consider doing that. By extending the wires, you could mount the relay almost anywhere for convenience sake.
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post #9 of 9 Old 09-16-2013, 06:37 PM
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Yep, a standard relay can not be substituted for a PWM relay that the WJ uses. Hooking up a regular relay in place of a PWM relay will create a firestorm inside the regular relay and burn it out in very short order.
Think of pulse width modulating as basicly it turning on and off really fast. Doing this, can allow the fan to speed up slowly and avoid the sudden high amp draw when it first kicks on and speeds up like if you were using a regular relay. And also can be used to control its speed.

'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, home made front hub conversion, hydroboost. Warn M10000 winch. Currently building a stroker.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
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