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Triggering aftermarket fan

scoob8000 on Fri July 11, 2008 6:56 PM User is offlineView users profile

I'm retrofitting an electric fan kit into the 91' Buick Roadmaster.

I have a thermostat switch to cycle the fan on and off as well as a manual "always on" switch.

Any easy way to trigger it to be on when the compressor is running?

I thought about tapping it into lead that activates the AC clutch, but the fan turning on via temp would feed back and turn the compressor on.

Or should I even worry about it? If you're sitting in traffic and it's not cold enough, flip the fan on manually.

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iciss.net - Iron City Impala SS Owners

scoob8000 on Fri July 11, 2008 6:57 PM User is offlineView users profile

FYI, when I say retrofitting, the car had a clutch fan so there are no existing fan controls.

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iciss.net - Iron City Impala SS Owners

GM Tech on Fri July 11, 2008 7:28 PM User is offline

One of the advantages to using relays is that aggravating feedback loop is averted-- I would not eventry that fan circuit without a relay- no common switch or thermostat will take the amps a fan motor can pull for very long-- if you don't use a relay- you will soon let the smoke out of the switch.&....

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Sat July 12, 2008 12:20 AM User is offline

Those fans use quite a bit of current so you need a relay and a seperate supply from the battery (with fuse). You can either use multiple relays with the contacts in parallel or one relay with diodes going to the coil to trigger the fan from different sources.

bigkev on Sat July 12, 2008 3:37 AM User is offline

is it just one fan? Relay would be really easy to wire up. A good relay to try is part #mr76, most places can cross that, usually they can handle 30 to 40 amps pretty easy. If you look at the side of the relay a little diagram is on it which you can use for wiring it up. Look in fog light sections of retail parts stores and you can usually find 30 or 40 amp relays for less than 10 bucks. a relay will also isolate the clutch circuit from the regular fan control when its not energized (the relay isnt energized).

bigkev on Sat July 12, 2008 3:40 AM User is offline

also, I would assume that your always on override switch is part of your fan setup. If you used a kit this switch passes low current to control a large current. you could have the relay feed the side that runs the fan all the time. I got a diagram of my homemade truck ac if you want to see it. Its a good example of using relays.

raylo on Sat July 12, 2008 7:51 AM User is offline

I just did this on my 1994 S-10 p/u. I got a set of late model Camaro dual elec fans and fabbed them up to my S-10 shroud.

You can get individual temperature controls and a relay to operate the fan. Or you can go with a more engineered solution like a variable speed controller. Either method can use temp sensors that either plug into the radiator fins or screw into a port in a water jacket on a head or intake manifold, if you have one available. I used a variable speed controller with the radiator probe and it works great. A little more expensive than just temp controller and relay but a very clean install.

Here is a link to a rather lengthy thread on my fans.
http://www.s10forum.com/forum/f107/electric-fan-q-s-357538/

Here is another link that shows the controller in more detail.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=FLX%2D33054&N=700+4294924500+400226+4294860934+115&autoview=sku

As for a/c connection you just need to tap the wire that energizes the a/c clutch and connect to your relay or controller. On GM it is usually a green wire.

Edited: Sat July 12, 2008 at 8:02 AM by raylo

scoob8000 on Sat July 12, 2008 8:09 AM User is offlineView users profile



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scoob8000 on Sat July 12, 2008 8:11 AM User is offlineView users profile

Yes, sorry.. I am using a relay, and simply using the thermostat and the switch both to trigger the relay.

As GM Tech mentioned, the only way around the "feedback" I can see would be using two relays. Or perhaps a blocking diode between the compressor clutch wire and the fan relay.

Raylo, thanks for the link

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iciss.net - Iron City Impala SS Owners

raylo on Sat July 12, 2008 8:19 AM User is offline

Yes, there are a lot of circuit diagrams going around most with 2 relays and probably a diode. The controller I linked has all that stuff built in and it is a solid waterproof assembly. Makes it easy if you don't have time to tinker too much with the wiring. The elec fans made a big difference for me in summer stop and go. Good luck!

TRB on Sat July 12, 2008 4:23 PM User is offlineView users profile

All you need to do is splice into the power lead at the LPCO switch. I prefer to do this on the power side. Wiring in a standard relay setup to trip the fan. Don;t have the part numbers in front of me. But the whole relay kit is like $ 20.00. Relay kit looks like the ones we include with our fans.



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scoob8000 on Sat July 12, 2008 11:38 PM User is offlineView users profile

Tim,

So if I'm following you right, the power lead to the LPCO should only be energized if the head unit in the car is calling for AC (defrost, AC, etc).

If that line sees +12v, even with the head unit off will that energize the compressor clutch?

If you see where I'm going, I'm trying to accomplish this setup with just one relay and keep it simple.

Is that relay kit and harness you sell available seperatly, if so got a higher res shot of it? Might beat me making my own harness.

Thanks again!

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iciss.net - Iron City Impala SS Owners

iceman2555 on Sun July 13, 2008 7:18 PM User is offlineView users profile

Replacing fan clutches with electric fans is become quite a fad. However, what many fail to realize is the total amount of air flow (cfm) that is necessary to cool and engine. Most of these aftermarket fans were designed as a supplement fan instead of a stand alone cooling unit. The 16' "S" blade type fan has a cfm rating of app. 1400-1500 free flow/1150-1300 flow across a typical radiator. This amount of air flow may be less than that is required to cool this small block. A suggestion would be to add dual fans to enhance air flow/cooling. A single fan that does not cool properly will affect many aspects of the engine cooling system....coolant temp...which has a direct effect on transmission fluid temperature.....excessive temps here will result in a break down of tranny fluid....read transmission rebuild....and of course...condenser cooling....possible excessive high side pressures.....decreased A/C performance.
These fans require app. 15-20 amps each. Insure that the cooling system has this amount of 'free' amps to operate the fans.
This year we have seen a drastic increase in 'tech' calls concerning adding electric fans to replace OE fan clutches. A suggestion would be to completely evaluate what is expected from these fans...the cost....possible lack of sufficient cooling vs. the replacement of the OE fan clutch assembly.
A personal opinion is that this single fan may lack sufficient cooling efficiency to cool your vehicle.....suggest to purchase another unit.....fit both for temp engagement/compressor engagement.
Also keep in mind that the engagement temperature should not be set so low as to result in constant fan engagement.
Good luck!!!

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TRB on Sun July 13, 2008 7:23 PM User is offlineView users profile

Quote
Originally posted by: iceman2555
Replacing fan clutches with electric fans is become quite a fad. However, what many fail to realize is the total amount of air flow (cfm) that is necessary to cool and engine. Most of these aftermarket fans were designed as a supplement fan instead of a stand alone cooling unit. The 16' "S" blade type fan has a cfm rating of app. 1400-1500 free flow/1150-1300 flow across a typical radiator. This amount of air flow may be less than that is required to cool this small block. A suggestion would be to add dual fans to enhance air flow/cooling. A single fan that does not cool properly will affect many aspects of the engine cooling system....coolant temp...which has a direct effect on transmission fluid temperature.....excessive temps here will result in a break down of tranny fluid....read transmission rebuild....and of course...condenser cooling....possible excessive high side pressures.....decreased A/C performance.

These fans require app. 15-20 amps each. Insure that the cooling system has this amount of 'free' amps to operate the fans.

This year we have seen a drastic increase in 'tech' calls concerning adding electric fans to replace OE fan clutches. A suggestion would be to completely evaluate what is expected from these fans...the cost....possible lack of sufficient cooling vs. the replacement of the OE fan clutch assembly.

A personal opinion is that this single fan may lack sufficient cooling efficiency to cool your vehicle.....suggest to purchase another unit.....fit both for temp engagement/compressor engagement.

Also keep in mind that the engagement temperature should not be set so low as to result in constant fan engagement.

Good luck!!!

Agreed, but I missed where the OP said they were replacing their OEM fans.



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Contact: ACKits.com

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