Larry Dunlap

my car alway overheats in the summer when its hot (which is everyday here in the summer), in stop and go traffic with the air conditioning on. As far as Ive noticed the second fan (passenger side) never comes on. Ive never seen it come on, it may come on while Im driving I guess. I replaced the sensor a long time ago and checked all the electrical circuits, they are fine. So I want to install a switch on that fan and put it on the dash. Ive got a nice little 10A switch, is that big enough? I was thinking about cutting the wire from the fant and spliciing on one wire to the ground of the battery, then one (with the switch in line) to the positive battery terminal. Also I would put a 10a inline fuse on the + side. Does this sound alright or is there a better way?

Dyno Don

iTrader: (7)

The fan motor needs at least a 25 amp fuse. Never cut the wires and hook a switch with voltage. Instead connect a wire to the green wire going to the sensor on the right side head and run it inside to a switch (amps not important) then run a ground wire to the other side of the switch. This way the relay and the fan fuse still works normal (no risk of short or fire). If the fan doesn't work then, check the fan motor to make sure it is good.

Definition: all the relay needs is ground to complete the circuit.

Larry Dunlap

Great. That sounds good. I can get a bigger switch and get an inline 25a fuse. So just cut into the green wire and leave it connected to the wiring harnes I guess right? Even though the fan never seems to turn on anyway I guess that would be better. So the switch just completes the ground. Thanks for the info

Larry

Dyno Don

iTrader: (7)

First attach a wire to the green wire (leave the green wire attached to the sensor) then turn on the ign. and touch the wire to ground and see if the fan turns on. You can use a 10amp switch but you won't need to use a fuse as the system going to the relay already has one. This way if you find out the fan motor is bad (and you replace it) you will have sort of a safety built in if you forget to turn on the switch. That way the sensor will turn it on when it reaches the preset temp.

Danno

Change the aux fan relay. To test the aux fan motor unplug the aux fan relay. Look at the socket, there will be 4 wires two of them heavy guage 2 lighter guage. Use a jumper of decent guage and with the key off you can jump the two HEAVY guage wires. The aux fan should run if the motor is OK. Don't fool with the relays, replace them both. More cooling problems with TG's were caused by intermittent fan relays than anything else. NAPA #AR-279.

Larry Dunlap

Im confused. I have two wires from the passenger side fan. one has a purple stripe and the other as far as I can see is black. I tried running a wire to each one in turn, then to ground as was suggested here. Didn't run either way. Then with the wir on the black wire, I accidentally touched the other end of the wire to the positive battery terminal. Bingo, fan runs. So fan is good, why wont it run completing the ground like was said here. I could hook up the fan to the positive but it was advised against here, not safe right? I appreciate any help

Larry

MdFormula350

not sure if u have seen these.

MdFormula350

i have the passengers side fan with a manual switch, works good.

its good to use the factory relays to operate the fans.

Danno

MD, the diagram you submit has the switch on the ECM side, not on the aux side. It will work that way, however you don't get the benefit of BOTH running as they do if you switch the aux on first. Just a thought.

MichaelGA

Where is the fan relay located?

MdFormula350

usually around the drivers side firewall to the right of the brake booster or around the radiator sides.

in that diagram i have the manual fan switch located on the same wire as the fan switch for the passengers side fan. when i flip the switch i ground the relay and the passengers fan comes on and off when i want it to and doesnt seem to affect the drivers side fan at all. so i am kinda using the passengers side fan manual switch first to keep cool and then if for some reason it doesnt work the drivers side should come on and if that doesnt work i still should have the passengers side come on as he final backup with the stock fan switch.

Larry Dunlap

The diagram is great but I guess Im really kind of stupid. Simple question

I have two wires coming off my secondary fan. Supposedly if I connect a wire to one and touch it to ground, the fan will come on. I could put a switch there. I opened a spot on each of the wire coverings and tried this with a wire and the fan didn't come on. The fan is good however, becuase when I touched the wire to the Pos battery terminal it came on. What gives? I just want to wire a simple on/off switch to the secondary fan.

MdFormula350

the easiest is just to take a regular toggle switch, then splice into the stock fan switch wire anywhere after the relay for the passengers side relay. and then hook that up to the switch and then the other wire going out of the switch goes to a body ground. that is the easiest and safest way to do it. so that switch will just ground the relay when flipped anytime when the car is on and turn that passengers side eletric fan on. i have been using the same setup for over a year i believe and it works fine, no problems at all.

the wires from the fan you dont want to mess with because you have just bypassed the relay and you are going to need fused switches and stuff like that because you are bascially trying to use the 12 volts right off the battery right to the fan and thats a no no because you already have the factory wiring setup all you need to do i put a toggle switch inline with the factory fan switch wire and now you are then using the relay which can hangle the battery volts / fan current draw (amps) safely.

Larry Dunlap

Oh I think I know the problem now. I was tying to hook into the wires right down by the fan. YOu are talking about the wire coming off the relay up by the firewall. That must be where the green wire that was mentioned is located Well it takes me a while to get it but Ill eventually get there.

MdFormula350

glad u got it.

91CamaroRS305

iTrader: (2)

this is wierd, i got my car out of the shop, the fan switch was replaced as well as other stuff i didnt have the diagnostic tools for, anyway, it worked until yesterday, the relay was bad, i had the the guy who fixed it look look at it again, i replaced the relay after the said it was bad, but the engine was warm and when i turned the key the fans didnt turn on, also i replaced the coolent stat and the hose nearly exploded cause it didnt open what gives?? now if i wire a switch to the ground on the relay will both fans come on or just one?(the switch is for an emergency

Larry Dunlap

hmm, I dont know about all that other stuff, but on a dual fan car like mine (and I assume yours) there is a relay for each fan. The Coolant fan relay is on the far driver side, then the fuel pump relay, then the "heavy duty" coolant fan relay, which controls the fan on the passenger side. MY regular fan goes on and off with the temperature, but the second one never came on that I could see, I replaced the sensor, checked the motor on the fan, ect. So I put the switch on the Heady Duty coolant fan relay. I mounted the switch on the fuse panel cover so I didn't have to drill a hole in the dash or something else. I works great. Whenever I get in traffic and the temp goes up close to the red zone, I flip on the fan and bingo, back down it goes. I just put the switch on the green wire as was mentioned (and I verfied as in my shop manual). Everyone should do this on these cars as the run so hot.

Danno

Maybe it was simply not hot enough. The engine temp has to at least 225 degrees for the primary fan to run in a stock dual fan setup. 243 for the aux fan, or as the A/C compressor pressure requires. There is no "heavy duty" fan relay, both are the same. If it is working correctly there is no need for manual switches it will stay in the safe range. If you ground the aux relay both fans will run, if you ground the primary relay only the primary fan will run. It is much simpler to make up a short spade jumper and carry it in the glove box and pull the primary relay and jumper it for continuous operation in a pinch than to muck up the car with additional wiring. The aux fan will rarely run unless the A/C is on since the pri fan will keep the engine well below 243 in all but the most extreme conditions.

91CamaroRS305

iTrader: (2)

i see, but the prob was the fans werent turning on, i already did a switch so both turn on, but yesterday they didnt turn on and the mechanis says the wire is bad somewhere going down to the sensor, but i did the switch and havent had a prob(even installed a nifty temp gauge on the left lower side of the dash)

Larry Dunlap

There is a "coolant fan" (which is the fan on the driver side) with a "coolant fan relay", and there is a "heavy duty coolant fan" (which is the one on the passenger side), and a "heavy duty coolant fan relay". Yes, both relays are the same but one is for the heavy duty coolant fan. At least thats what it says in my GM Shop manual.

I dont understand the problem. You are saying the fans run with the switches but not otherwise?

RPM WOT L 98

iTrader: (3)

Ok so here's a question then. A few years ago I decided that 210 deg was too hot for my liking so I jumped the relay for the primary fan to run when the ignition is turned on, and at first wired the secondary fan to do the same. This worked great, the car never went over 160. But then I started to blow the fuse for the fans in the fuse box. It is a 20 amp fuse, after replacing that a few times, foolishly I put a 30 amp fuse in it and all was good until I realized how stupid that was. So I left the primary fan jumped on the factory wiring through the 20 amp factory fuse, and wired a dedicated circuit from the battery to a toggle switch for the second fan. This still works great. I like the idea by MdFormula about just grounding the relay of the secondary fan, but that means that both fans would be run on the factory 20a circuit and that won't work for some reason. I tried one fan today on a 10a fuse and it blew instantly but it works on a 15a fuse!
So, can I possibly run both fans at the same time on the same circuit if it is only 20a and each fan seems to take more than 10a??????

Also I would like to wire up a factory foglight switch to run the second fan. Can I run voltage from the battery to it, or would that be too much amperege for it to handle. And if anyone who has used a factory foglight switch can give some ideas on how to wire it up I would greatly appreciate it.

Thanks guys.
Mark

Danno

They refer to the duty cycle of the fan. The primary or driver side gets the most use. Aux fan only when its really hot or when A/C pressure requires it.

RPM WOT L 98

iTrader: (3)

One more question here.
I grounded the relay on the pass side fan, and it works fine. But for some reason the PCM is telling the primary fan to come on then the car is started. Not when the ign is turned on, but when you crank it, and stays on. I am guessing that the PCM is grounding the primary relay but what is telling it to do that? The temperature of the car does not matter, and I even unplugged the relay for the secondary fan and the primary still cuts on at startup. Any ideas what could be telling the PCM to ground the relay?

Danno

Whenever the ECM sees the aux fan sw low before the operating temp reaches the point at which primary comes on the ECM will default turning the primary on as well. There is an input on the ECM that is fed from the aux fan sw and A/C pressure switch.

DreamState21x

My primary comes on when you crank the car also, and stays on. But where the aux fan plugs into the sesor on the side of the block the male connector broke and fell out of the sensor, I am going to try the switch like everyone is talking about off the green wire, just so i can turn it on when i won't (cooler is better) but if my primary comes on as soon as the car is cranked and stays on why not have both fans on all the time??? any reason why not to have them both on all the time.????? just curious..

RPM WOT L 98

iTrader: (3)

I had both fans on for a while and it was fine, car ran real cold. (160 thermo) There's no need though.
Does the AUX fan work, is the harness OK??? I finally figured my fans out and it turns out that the reason my primary was coming on at startup was bc the AUX was on and the ECM went into default mode and thought since the AUX is on that means the primary needs to be on too. This might be a reason why your primary goes on when you are cranking. It is also possible for the coolant temp sensor to be faulty and tellling the ECM that the motor is hot enough for the primart to cut on. it is on the front of the intake.
Check to make sure the AUX fan actually works, and if so then follow the harness for the primary bc you might have a short somewhere.
That your pri is on at startup is good all you have to do is run a switch for the AUX but I'd find out where the fault is in the pri harness bc you just never know what it might be and what it might cause. Shorts are not a good thing.
Hope this helps.

DreamState21x

cool, thanks man now that I know why the primary is always on I'll check for the short and then the temp sensor.. thanks..

DreamState21x

ok this is what I did, I just ran a wire from the green one to a ground and now they both are on, which is what I wanted, they also come on now when I turn the key to accesories, which is cool cause you can use that to cool down your car if it ever runs hot... Thanks for the help

cmax5

My aux fan (passenger side) does not come on even if the temp guage hits the red zone 266F (130C in my GTA) with the a/c off. The driver's side fan is on but the aux fan will only come on if the a/c is on. Is the problem the temp switch on the block or the relay? I don't have a schematic of the fan wiring other than from the Barron's book but it only shows one fan anyway.

If there is only one relay for the aux fan that is controlled by the a/c and the aux temp switch then I imagine the problem is the temp switch not the relay. Where exactly is this located and do I have to remove anything to see it? I've looked from the top at the rear passenger side of the engine but don't see anything so far.

The main driver side fan kicks in at 230 F or above. This seems too high a temperature to be kicking in. I also found the two matching fan relays, part number 10038311 and they were located by the radiator on the passenger side. They are partially obscurred by the air filter container.

afnunez

I connected both fans before the relays ( so no relays at all) to a single wore and ran to a manual switch inside my car. Is that bad to run both fans on a single wire? What ampage do I need to run as far as an inline fuse ?

Shmuckus

My aux fan (P side) comes on at around 170F (assuming the temp gauge is correct) but the primary fan (DR side) has not come on for many years, even when heating the engine up to 250F. With only the aux fan running, the temp will rise to 236F then settle at 225F, for both idling and driving. Four years and 45k ago, I replaced the cooling fan switch (P side, lower engine) because the P side fan stopped working, and within the last few weeks I installed a new thermostat, temp engine switch (DR side, lower engine), coolant temp sensor, and the DR side fan motor. Also, I've checked the primary and aux relays and they are good, and the new fan motor is ok because I attached a test wire to the green/white wire before the relay, and then when the test wire is grounded, the DR side fan will spin. Any thoughts as to why the DR side fan does not come on in a normal hook-up?

Reid Fleming

iTrader: (2)

Shmuckus, it sounds like you're on the right track so far. Check out my sig to see if there is anything you missed.

Shmuckus

Mr. Fleming...Thank you much for the info and diagrams. I'll keep you posted as to my progress. Earlier today I attached a ground wire and a wire connected the green/white wire to a toggle switch, so now I can at least manually turn on the DR side fan with a flip of the switch if need be.

ninetyone

iTrader: (2)

NO, just cut the wire from the fan sensor on the block on the passenger's side and take that wire and ground it to the body of the car. Fan will always be on. OR if you want a switch to turn on whenever you want. THen take that wire and wire it to an on/off switch and then take another wire from that switch and ground it. Tada, an instant fan switch.

ninetyone

iTrader: (2)

That sounds backwards. the primary fan comes on at 226 and the passenger side fan on at 240-245 degrees.

Ron U.S.M.C.

I run a 16in primary fan with this very simple adjustable thermostat controlled switch and it works perfectly
Here's the wiring diagram I used. It is not the diagram that came with the controller .
http://www.autozone.com/autozone/par...ier=267187_0_0_

Biggd4355

No on talks about the overheat switch which is located on the engine block. It is a simple ground. When the engine reaches overheat, the wire is grounded and the fan turns on. I would like to see a how to replace both wire and switch.

Biggd4355

you may want to go to a 30 amp for the fan.

Bigfoottpi11

You dont need any type of fuse, just connect the wire to an on/off switch and then to ground. Its is simple thing. Ran mine like this for years and years , no issue.