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electric fans - A/C question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jms, Apr 28, 2002.

  1. jms

    jms 1/2 ton status Author

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    Installed two electric fans yesterday - btw, thanks to all who responded to my fan clutch question.

    FYI, I used two Perma-Cool 14 inch pullers. For those who consider these fans, I recommend to do a quick wiring to check fan rotation - Perma-Cools instructions as to what wire is pos or neg were incorrect. I went with the adjustable wiring kit. Not sure about the temp sensor - it is a probe that is pushed between the radiator fins, we'll see how long it stays there. Painless makes a kit that reads temp from a real sensor in the manifold; that may be a future option. The Perma-Cool kit comes with an A/C override, leading to my question:

    What would be the best place to get an electrical signal "A/C on"? At the evaporator? Idle-speed solenoid at the carb? Or at the compressor - which would turn the fans on only when the compressor clutch is engaged? Not sure whether that's good anyway, it may lead to too many on/off cycles. I've looked thru my Hanes and Chiltons and can't find an A/C relay, or any other electrical info re A/C, but then again it was a bit late yesterday. Advice's greatly appreciated, thanks, michael

    P.S. Summit has by far the best price on the fans - I've used the nylon straps to mount the fans but for trailriding braces are necessary - it's amazing how much empty space there is now at the front of the engine.
     
  2. Michael

    Michael 1/2 ton status

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    I would probably tap into the A/C clutch signal.
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I will start by telling you about the purpose of an override switch. The override switch is designed so that when the A/C is on your electric fans come on also if they are not already. When the A/C is on it is robbing horse power from the vehicle and if you were pulling a hill the vehicle could start to overheat if the electric fans aren't on. I would not worry about the fans cycling off and on too many times as they are usually on more than off depending on what temp they are designed to turn on at if you do have an adjustable regulator. Now as far as where to catch the source for the override switch power, I also would have to agree that the A/C clutch power lead would be your best bet since that is where the compressor gets its power to activate the A/C.
     
  4. jms

    jms 1/2 ton status Author

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    Michael, Scott, thanks for the replies, I'll tap into the compressor clutch to get the override. I haven't had a chance to dial in the temperature feature yet. Anyways, I've taken a few pics this morning for anyone who might be interested:

    http://www.desertrider.net/images/Fans2.JPG
    <a target="_blank" href=http://www.desertrider.net/images/Fans4.JPG>http://www.desertrider.net/images/Fans4.JPG</a>
     
  5. 76chevy

    76chevy 1/2 ton status

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    You may be able to pull an A/C signal from the wires that attach to your fan clutch/compressor. They should plug into the back of your compressor. The compressor won't turn on unless your controls inside the cab are set to A/C so somewhere on the back of your compressor you should be able to find the wire you are looking for.

    Those fans blow quite a bit of air don't they. I think they have the best airflow and price that I've seen.

    I'm currently running one fan but later I will go to two once the A/C is up and running. Like you said, the fans need metal straps to support them if you go offroad. I picked up some straps from Lowe's that are pretty stiff. I'm going to rebend them so my fan sits closer to the radiator. It is out far enough now that I can put 3 of those pads that came with the fan between the fan feet and the radiator. I want to get it back to about 1 of the supplied feet so I get better flow through the radiator.

    I have an adjustable thermostat too. I bought mine at Autozone and it adjusts from 32F to 226F(?). I don't know what mine is set at now but it is set a little above normal opperating temature.

    Did you notice a performance increase? I sure did but I've got a 76 that doesn't have as much power as your 85.

    Congradulations on the install. Do us a favor an build a metal shroud or use metal to mount the fan so we don't get an emergency email saying your fan made your radiator leak and your stuck in the middle of Death Valley. Speaking of Death Valley, that really ought to give your new fans a test.
     
  6. jms

    jms 1/2 ton status Author

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    Well, I did take the signal from the compressor clutch, works just fine, thanks to everybody for the advice. Drove the truck to work and back today, and cannot really say much about the fans because it was rather cool today anyways. Haven't measured, but from judging the gauge I'd say they come on at about 185 or so. Cool day like today, the fans don't come on much at all. They do create quite some airflow and and can pick up a piece of paper flat to the grill - couldn't do that with my clutch fan /forums/images/icons/cool.gif.

    I'm planning on building braces from top to bottom of the rad to give extra support to the fans, not sure whether I'll use steel or aluminum (L or U channel). Game plan is to keep the fans right where they are (i.e. mounted with the nylon straps) and add the braces as extra support. I'll probably use metal for the shrouds, although I'd like to find some heat-resistant plastic if possible. I'd like to use it not just for fan shrouds, but also for a splash guard to cover the open space between the rad and the engine - I'm thinking that would channel all that extra air in the engine compartment back and out where the headers exit the engne compartment, and possibly reduce temps there as well. Not sure about that though, we'll see.

    The only reason I'm NOT in Death Valley right now is lack of time (yeah, that, and the job, duh...); as a matter of fact it's gotten so bad, I'm not even sure I'll be able to make it to Moab in the summer for the Blazer Bash. I had to chuckle when you mentioned DV as an example for a radiator test; in fact DV is one of my all-time favorite places, try it in August without A/C (been there, done that, felt great, gives you an idea how it must have been in the old days!)...and since I usually go alone, rest assured there won't be an emergency e-mail if this fan/radiator thing fails.../forums/images/icons/cool.gif
     
  7. BozoWise

    BozoWise 1/2 ton status

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    Hey 76chevy

    What temp switch did you get from autozone. How much did it cost? Where does the temp sensor mount. I have my fan running of switched power and it has a manuel kill switch for water crossing. But I might look into the temp sensor for the few times I do drive the blazer in the cold (not much in Southern NM)
     
  8. jms

    jms 1/2 ton status Author

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    How did you wire the kill switch? In the power wire to the fan relay? Just a switch or another relay?
     
  9. 76chevy

    76chevy 1/2 ton status

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    I think the adjustable temp switch was $17.99 plus tax. It is for a different fan manufacturer but it works. It was just below the electric fans that Autozone had. Don't buy their fans though because they don't pull very much air.

    The switch has a sensor that I stuck in the radiator next to the upper radiator hose. I mounted the switch to the side of the radiator.

    I bought that one because it was available right now. Not very fancy but it has a lot more adjustability than the one PermaCool offers.

    PermaCool does have one that has a 170F switch that mounts in the intake manifold but it isn't adjustable and I think it is $24.99.

    Overall, I'm happy. It is easy to adjust and requires a screwdriver so you can't accidently adjust the temp. The instructions did recomend a 30 amp fuse to protect but the fan/fans but that didn't come with the install kit. I used an old 30 amp inline fuse holder that I had. I may change it later to one inside the cab once I put in an on off switch.
     

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