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Unread 10-13-2014, 07:28 PM   #1
NewTo98JeepGC
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How To Keep Electric Fan Running After Key Off

Hello,

I plan to install an electric fan for my 98ZJ. (I live in Florida and do a lot of in city stop and go type driving). My questions are:

1. How to keep the fan cooling the engine after I turn the key off.
2. Is it necessary to to keep the fan running after the engine shuts off?
3. If it is, what relays or device I need and how to wire it into the system?

Thanks.

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Unread 10-13-2014, 07:59 PM   #2
firsttimeZJ13
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If you keep the fan running after shut down, all your doing is draining your battery which could effect startup. I wouldn't recommend it. If you really want to. You could have to ACC wire hooked up to battery power, but then you have to remember to turn it off or find a timed switch to shut it off. It's no necessary though.
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Unread 10-13-2014, 08:56 PM   #3
mikem350
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If you add an electric fan, it better be high capacity and sealed to the rad with shroud etc. You need this to provide enough airflow especially at slow and idle speeds with A/C!! These things draw a lot of amps, maybe require an alternator upgrade.

And I am in FL too, and added a jy trans cooler to my '98...and serviced the trans filter. BTW, the dealer filter kit includes a neat re-useable hard plastic gasket. Nice!
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Unread 10-14-2014, 08:07 AM   #4
NewTo98JeepGC
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Thanks,

I am heading to JY to get a Mark 8 fan today.
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Unread 10-14-2014, 08:18 AM   #5
HighLonesome
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You will need a new battery every couple years doing that.

But yes it is good to keep it running. But a timer is the way to go.
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Unread 10-14-2014, 11:03 AM   #6
NewTo98JeepGC
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Quote:
Originally Posted by HighLonesome View Post
You will need a new battery every couple years doing that.

But yes it is good to keep it running. But a timer is the way to go.
After I changed the thermostat to 195 (PO had the 180 in it), the engine runs a little better and mileage gets a little better but the normal driving temp is right at 210 (it was around 195 to 200 with a 180 thermostat). However, every time I do short stops in town and restart the Jeep, the temp gauge read around 230. Then temp drops back to 210 afterward.

I was hoping an e-fan with bring the driving temp down to 195-200ish and keep cooling the engine for another 5 minutes after I shut the system off. I think this way will prolong the life of the engine.

I have a Costco battery so if it dies in 2 years, I get a new replacement for free
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Unread 10-14-2014, 11:36 AM   #7
HighLonesome
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What kind of thermoswitch are you using? The adjustable ones with a radiator probe can get stuck on and kill your battery completely. I have had nothing but trouble with this POS:
http://www.amazon.com/Hayden-Automot.../dp/B000C39C6I
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Unread 10-14-2014, 06:35 PM   #8
mikem350
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ALL cars heat soak after you shut off the engine, with temp rise like you see...

And run a little hotter than the thermo rating. The 195 is where the thermo BEGINS to open. But thanks for the info on swapping to the 195, I was thinking of going 180, but will stick with 195!!
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Unread 10-14-2014, 08:34 PM   #9
NewTo98JeepGC
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I got a after market fan with TYC Radiator Fan Motor (TIY-307260)) from a 95 Thunderbird, 4 Volvo fan controls, inline temp sensor adapter from Saab 900, I just need to get a sensor to hook up the system. I need advise on:

1. How to take the old sensor from the adapter?
2. Is the TYC a good fan motor or I need to continue looking for OEM motor from JY? If I do, how to identify the motor?
3. Which brand of temperature sensor should I buy/order.

I am going to another JY on Friday to hunt for another Saab inline temp sensor adapter, just in case.
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Unread 10-15-2014, 09:29 AM   #10
zjosh93
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If you want it to run the same amount of time after shut off every time you turn it off you can just buy a time delay relay. Finding a 12V version rated at the amp load for the fan might be tricky but you could always run the main relay off the time delay relay.

I use a Taurus fan in my turbo car. My two relays are mounted in a Saab ABS relay box. http://www.supermotors.net/registry/media/1012950 Nice weather sealed piece that hold two Bosch relays and a few fuses. Made my own inline sensor holder and used stock early 80s Chrysler fan switches. Low speed at 185 and high at 200. http://www.supermotors.net/registry/17591/82709
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Unread 10-15-2014, 11:34 AM   #11
jeepjeepster
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Ive had a 180 stat in my 94 for years. Routinely gets 21-22mpg and runs nice and cool.

Only issue I have is the heat isn't as hot in the winter. With temps below 0F last winter I often times would stay chilled to the bone driving 20min to work with the heat on high. Im a cold natured person in the winter though. Once my bones get cold it takes a lot of heat to warm me back up.
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Unread 10-15-2014, 10:18 PM   #12
NewTo98JeepGC
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Quote:
Originally Posted by HighLonesome View Post
What kind of thermoswitch are you using? The adjustable ones with a radiator probe can get stuck on and kill your battery completely. I have had nothing but trouble with this POS:
http://www.amazon.com/Hayden-Automot.../dp/B000C39C6I
Basically, I am using this wiring diagram,

http://www.jeepz.com/forum/attachmen...lvo-wiring.jpg

with either a BMW or Porche 944 or VW thermosensor, Volvo Fan Controller. My question now is how to tap into the A/C wiring so that when the A/C is turn on, the fan goes to high speed?

Thanks.
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Unread 10-15-2014, 10:30 PM   #13
NewTo98JeepGC
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Quote:
Originally Posted by HighLonesome View Post
What kind of thermoswitch are you using? The adjustable ones with a radiator probe can get stuck on and kill your battery completely. I have had nothing but trouble with this POS:
http://www.amazon.com/Hayden-Automot.../dp/B000C39C6I
Basically, I am using this wiring diagram,

http://www.jeepz.com/forum/attachmen...lvo-wiring.jpg

with either a BMW or Porche 944(http://www.autoatlanta.com/Porsche-9...160648100.html) or VW thermoswitch, Volvo Fan Controller. My question now is how to tap into the A/C wiring so that when the A/C is turn on, the fan goes to high speed?

Thanks.
img_20141014_205523-1-.jpg

img_20141014_205512.jpg

img_20141014_205552.jpg

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Unread 10-15-2014, 10:52 PM   #14
NewTo98JeepGC
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First photo was the Volvo fan controller that came with fuses for the high and low speed.

Second photo is the Saab 900 thermo switch adapter. I am going to the JY tomorrow to see if I can get a couple more adapter in case I break the one I have while taking out the old switch.

Third photo are the fuses. It seems the high side has a 35A fuse and low side has a 30A fuse with metallic cover. Are they good enough for the Mark VIII fan?
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Unread 10-16-2014, 09:21 AM   #15
HighLonesome
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Quote:
Originally Posted by NewTo98JeepGC View Post
My question now is how to tap into the A/C wiring so that when the A/C is turn on, the fan goes to high speed?

Thanks.
If the 'volvo' unit handles the required function of not applying 12v to both the hi and lo windings at the same time (smoking the fan motor), which it probably does, then you would tap the AC compressor enable wire and make a connection to pin 2 on the volvo unit where the highside temp switch connects. You need a diode too so your efan does not turn the compressor on when it shouldn't be.

Making that connection would run the fan on high when the AC compressor cycles. Not optimal because the fan should run whenever the AC system is on, not just when the compressor is on.

I just put a rocker switch in the cab to force the fan on high when the AC was on.
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