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Discussion Starter #1
Guys I have a question. This is my situation. I have a LS in my 67. Ands I just put a single but dual speed on the car. Now the computer has leeds for primery and secondery fan, but mine is not duel fan. So can I in any way wire so that when primery kicks in would run on the slow speed and when the secondery kicks in the first one would sut of the electrik and run just the fast speed.
If it is doable can you please draw me a diagram so I can wire my fan. Thank you thank you.
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I need to know more about the two speed fan. I would guess it has two hot wires and a ground. If so does energizing one wire turn on slow speed and then energizing other wire turn on high speed or does energizing both turn on high speed? If you can answer this or tell me who makes the fan, I can draw a schematic of the relay wiring and email it to you.
 

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Discussion Starter #3
Thank you very much. Fan has 2 hot and one ground wire as you said. One wire is for slow the other wire is high speed. It's a ford fan.
Thanks again.
Ismail
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Ismail, one thing to remember when wiring the fans using the GM computer. The control or trigger from the computer is the ground, not the positive. I wired the negative side of fan to the computer leads and the positve side (of fan) to a relay that was wired into an ignition key source.

Is the fan is out of a taurus? Does it have a fan shroud built in? I had one in my car for a while and it worked well. One word of caution, the high speed fan draws alot of amps, use at least a 40 amp relay and at least 8 or 10 gauge wires! If not, it will burn wires (personal experience). Find out what size relay it came from from the factory (donor car). Just figure out which lead is for low speed and which one is for the high speed. Use the primary fan lead for the low speed and the secondary for the high side. Hope this might help you.
 

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Discussion Starter #5
Chris, thanks for reminding about computer wire being ground . I knew about it but forget.
Fan has a shroud and like you say has a heavy gauge wire for the high speed. Ilooked for the relay but could not be able to locate even though I found it probably would be to confusing for me to figure out about the wires. Some relays have no numbers on them.
Ismail
 

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Originally posted by 130fe:
The control or trigger from the computer is the ground, not the positive. I wired the negative side of fan to the computer leads and the positve side (of fan) to a relay that was wired into an ignition key source.
Are you sure about this? Negative side of the fan to the computer? I could see the relay wired to the computer, but not any fan lead. Otherwise there is no point in having a relay. I don't think the computer can sink 30Amps or so of current. But then again, I don't own this model year and can't be certain.

-dnult
 

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You must use a relay to power the fan! Power each hot wire and see which one is high fan speed control. Its probably a fixed magnet, dual windings DC motor. if so, relay the high speed hot wire, to a good 12V source. If you can identify a single high speed power fan wire, isolate the low speed (Provide no power), and use the high speed hot wire. If the ecu output is a ground 0V output for fan ON, wire the relay control input to Ignition +12v (ignition on) and isolate ground from the relay and let the output of the temp control ecu provide ground to the input of the fan relay.
I would verify the output state of the fan control of the ECU before doing any wireing to the ecu. Make sure the control output is either ground (0 Volts = on) or +12v = on. Switching the +12 volts is more conventional, but make sure! If its 12volts = on, provide the ECU output to the relay input, and provide ground to the relay.

Hope this helps, However, I would get a decent wireing diagram before wireing to the ECU. You only get one chance to screw it up!
 

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Are you sure primary and secondary is low and high speed temp control . Could it be engine temperature control and Air conditioning condenser cool control?
 

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Discussion Starter #9
Thank you guys for the help. I'm sure that the ecu grounds the fan. I/m not worried about the a/c bec. computer would sense the load anyway.
I'm waiting for 1 2 RUN, To draw me diagram with relay to run the primery first and when the secondary comes on primery shuts of.
If not I will just use the high speed as of now.
Wish had a duel fan but I have this one and fits realy good so got to use it.
 

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I'd get an LS1 schematic and not rely on someone else. If your computer is not meant to handle a 30Amp load it will go POOOOF! Suppose the grounded output is a FET with 0.2 ohms of on resistance. That is equal to 180 watts of power disapation. Your computer must have a hellova heat sink to handle that for any length of time. I'd double check your facts.

-dnult
 

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dnult, just to let you know, I converted my 68 to EFI similiar to ismail (see my sig). I got that information from the Painless Wiring Tech. I have not had any problems with my set-up. They told me most computer controlled vehicles trigger components through the ground (so that it won't fry the ECM, PCM, ect.) Have you ever tried an EFI conversion? It is a totally different animal than the standard carb motor. I am by no means the "expert" but learned alot about EFI swapping into an older vehicle when I did mine. I am giving him my own personal experience to try to help him. Try not to judge others so quickly. I would never purposely give any bad info to fellow club members.

Ismail, the painless wiring website has a good picture diagram on how to wire a relay (in tech tips section). I used 2 30 amp relays and 2 30 amp circuit breakers. If you have any doubts, I would recommend calling their tech dept. at 1-800 423-9696. They are a reputable company that puts out a good product.


I put a LT1 dual fan set up on my factory 23 inch radiator. All I had to do was trim the shroud around the radiator hoses and used the factory top bracket and made my own brackets for the bottom. You can get the fans on Ebay for approx. $75 and it looks really clean.
 

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Discussion Starter #13
Criss, thank you for the advice. I just got a standart size aluminum radiator from summit and I was looking at the factory dual fans and seemed like they are big. I wish got the wider radiator as in big block so probably I would have more roomto to fit a twin fan. But anyway I had this single dual speed fan and I think it will be ok to cool down the LS1. 1 2 Run e-mailed the diagram for relays to work with computer. \Ismail
 

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Ismail, no problem. You will enjoy your car even more than before (I did). No more adjusting the carb, starts everytime, better fuel economy, ect. How much more do you have to go before you get it on the road?
 

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Discussion Starter #15
Cris,
When I hook up the radiator/fan I need a driveshaft. bleed the brakes, bleed the clutch master and install the missing front grill and light. I could drive it after that. But I really need a paint job pasenger side quarter and a driver side door (the one on the carr is very old and dingy.). Next year I will get it painted hopefuly.
 

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Chris, I'm interested in EFI, but currently carberated. I have done some EFI conversions on other GM Camaros, but not my first gen.

My comments about connecting the computer to the fan come from my electronics back ground. You must have some specific information about your computer that says you can drive the fan from the computer. But it matters not whether you provide ground or hot, the computer must be capable of dissipating the power as heat. So if someone told you that because you're switching ground it's ok, I'd beware because that person is not telling you facts, but what they think.

Apparently the computer you're using is much different that any other I've dealt with. If it were me, i would still drive the fan with a relay, even if GM says the computer can handle it. Relays are much cheaper than high priced driver modules inside the computer - a non repairable part.

-dnult
 

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Dnult, the GM computer triggers a relay (ex.Bosch 30 amp)that controls the fan. It uses the ground pin of the relay to trigger it. The relay is powered while the computer triggers it on and off. It might not work the same way on an aftermarket EFI set up. I TOTALLY agree with you about using a relay for a electric fan, fuel pump, ect. If you don't you are asking for trouble.


[ 07-07-2003, 01:19 AM: Message edited by: 130fe ]
 

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dnult you seem to have a good electronics head. If you like I can send you the drawing of the two relay set-up that I sent to ismail. It's always good to have a second opinion. The relays have 40A N.O. and 30A N.C. contacts.
 

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Though my post got lots, but see it's there. Wish I could delete it


-dnult
 
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