My situation is this:

I have an 87 305 Camaro, 195* stat, live in Indiana, so I've been driving around (short distances) most of the winter without an operating cooling fan. Temp Gauge reads acceptable levels; radiator doesn't usually even kick in on my short drive to work.

Obviously, I need to get the fan working. The other conditions are: no radiator/fan shrowd, fubar-ed fan relay, fan is currently grounded, with power wire connected to the battery with a clamp whenever necessary. I've never done any real wiring, and I have read the tech article and lots of previous posts on this topic..still have some questions

I have two diagrams, and I'd like to know if anyone thinks one or the other is better, and where I might need improvements. Open to any suggestions.




Thanks in advance!

 

Your first diagram is really close to what the car comes with (except the ECM replaces the toggle switch).

Incidently neither of your relays will work because they are grounded on both sides.

connect: hot -->toggle switch--->relay--->ground

 

Be sure to fuse the connection to the battery...

 

Your first image was almost correct.

DO NOT wire any hot 12V wires to a toggle switch. With the ignition on, your fan relays ALREADY have 12V. What is missing is a ground, either thru the ECM, AC pressure switch, or fan temp switch, depending on application.

I dont know why people keep on insisting to add a 12V toggle when it comes to these fans. You could do that, but it's still NOT going to turn on the fans when you want to. It is USELESS to do that. Unless you want your fans on, with the ignition off, like waiting in line at the track.

 

Omar, I'm missing lots of wires and the ones that are left from the factory installation (for the fan relay in particular) are in really bad shape. That's why I wanted to run this simple circuit to manually control the fans...

I'm planning on using a 30 amp fuse (from the battery to the relay) with a 30 amp relay.. but should the fuse be less? And in theory, without the fuse, the relay would blow before any overload occured correct?

The diagram you provided is great Deadbird, any suggestions on a) which fuse to use in the fuse panel
and b) where to house the relay, inside the cabin or in the engine compartment?

...ohhhh yeah, should the fan still be grounded?

I appreciate all the help guys...:hail: I bought the Haynes guide to basic automotive electric systems, but it's nice to have a head start and some tutoring.

James

 

My diagram is a bit vague (it was a quick hack) I know but, yes, the fan still has to have a ground.

Awhile back someone posted the amprage draw of OEM fans and if memory serves me correct, the initial kick on current was around 15a and the continous draw was like 7-8a. I would start with an inline (direct battery) fuse of 15-20a. To gamble that the realy will burn it's contacts before the wire catches fire is not a risk I'd personally take.

Make sure the direct power cabe from the battery thru the relay to the fan is at least 12ga wire. OEM wiring had dual fans and the ECM & MAF (on my car) running off a 20a fuse (the fuse weatherpack shortly off the battery). I discovered that both fans running will pop the fuse with a quickness thus defeating the purpose of either fan all together.

I ended up rewiring mine (for asthetics (sp?) ) using a 20a for both fans (which seems to be alright under testing conditions) and a 10a for the ECM/MAF burnoff/ETC.

A solutiion for a toggle switch is to buy a JET switch that grounds at 200º and ungrounds at 175º that goes in your pass side head between the 6 & 8 exhaust port. $40ish (less actually) my be too rich for you but, I found it worth the $ just to not have to deal with the toggle switch (the JET switch would replce the toggle)

It's all up to how you want it to work really.

My setup...

http://www.deadbird.org/tech/fans.jpg

 

DeadBird - great quickie diagram. If I had some decent schematic software at home I'd make one too.

Omar - I'm afraid your diagram is wrong. The toggle switch you have there does nothing except connect ground to ground. Current goes is a closed path.

 

You need to study the circuit better, understand what is going on, and re-read my original post. My diagram is referring to the ORGINAL wiring in the fan circuitry

Yes, the toggle switch connects a ground wire to a ground wire. but what you FAIL to understand is that there is an open in the ORIGINAL ground wire...that open is closed via the ECM, fan switch in the passenger cylinder head, or AC pressure switch.

How do you think those three items take control and turn on the fan? By giving the relay 12V? NO!!!! By giving the relay ground. Hence my ground toggle switch.

Do you really think that your one wire fan switch, installed in your cylinder head, is somehow putting out 12V? Yeah, ok...

 

DPS, if your stock fan wiring is FUBAR, and you want to start over, then do this:


Get yourself a relay and wire it up like this:

86 - 12V ignition switch power

85 - to toggle switch. (other side of toggle switch to ground)

30 - Nice, big gauge wire straight to the battery. 30 amp inline fuse.

87 - to positive on fan.

You can permanently ground the negative side on the fan.

I am pretty much explaining deadbird's diagram.

This is just one of several ways to power your fan(s). As suggested, you could also use an adjustable Hayden switch in line. This would allow the fans to turn on at a pre-set temp, and you could still take control with your toggle switch. I personally think that is the best way to go. So you dont have to worry about turning on your toggle at the right time, leaving your toggle off when it's too late, or turning the toggle on when it's too early.

 

Hypersensitivty doesn't look good on you Omar. Don't get bent out of shape because somebody points out a mistake or disagrees with you. Remember, Arguing on the internet is like running in the special olympics.... Even if you win your still a retard.

I got an Idea why don't you repost your diagram and trace out the current path in red so an idiot like me can see it. (keep in mind that curren goes from a source to a sink)

Thanks alot.

 

Incidentally, I know what your trying to say. However, your diagram doesn't reflect that, and that's what I'm trying to say.

 

I just saw this.

Resistance is a function of temperature (Voltage is also a function of temperature in the case of a thermocouple) The ECM measures the current thought that one wire (the temp sensor does not produce 12V) the ECM can tell the resistance and therefore the temp by measuring the current E=IR ==> R=E/I by knowing the resistance the ECM can tell what the temperature is, then ground out the fan relay which is supplied by a 12V source.

 

The temp sensor does not produce 12V, and the ECM grounds out the fan relay....Um....exactly what i said.

I have also said that on the ORIGINAL stock wiring, suggesting a 12V toggle switch will do nothing.

Trust me, I am far from bent out of shape. I have both my fans wire thru a toggle for full control. The person that may or may not be bent will be the person following ignorant or bad advice.

Here is a step better. A scan from the 89 GM manual.

 

Omar's diagram is right (edit: his revision of the original hand-drawn diagram, not the scan, it seems we posted at the same time), if the ground on the relay is the "trigger" lead to the ECM (as he stated). If the ground in that diagram is the relay ground, then what 86irocZ stated is true. In other words, the diagram sucks too much to get into an argument about. There needs to be an internal schematic like deadbird's added into the relay box.

Also, Omar was talking about the temp switch not the temp sensor. The temp switch is simply another path to ground for the relay. The temp sensor is a feedback device which gives the ECM information to make a decision whether or not to ground the fan relay. I have to agree with Omar on the switch matter. I'd rather wire a toggle switch to provide a path to ground to activate a relay which powers a fan, than to wire 12v through a switch to activate the same relay. It's just safer electrically.

 

no

 

The sensor on the driver's side head is the temperature gauge sender. The sensor on the intake manifold is the CTS, which provides a coolant temperature reading to the ECM, which, incidentally, controls the fan under certain conditions. The switch on the passenger side head, is a "fan temp switch", which also controls the fan.

 

 

Here's the relay I picked up... or at least the back of the package

I was about to post something really stupid when I went back, reread all the posts, and discovered that Omar's magical numbers (85,86,87, 30) could all be found on the package! It all makes so much more sense now...

Except, what do those numbers actually stand for?

Again, thanks for all the help guys...

and if you wanna help me out with my performance problem, visit my performance problem post

James

 

where did you get that relay from??? i need to do this exact thing as well for my 305.

 

Just in case anyone else out there is ever looking for this relay, I bought it at Autozone for like $4... it was with the headlight and headlight wiring harnesses, at the bottom of the shelf.

An update: I ran all the wires through my firewall and wired my relay. Haven't grounded the toggle switch yet because my battery terminal plugs are like rounded and I need to replace them before I go any farther... headed out to Autozone for just that, right now..

Also, if you don't mind, I'm probably going to contact the electrical guys that posted here... I think I'm going to make an Idiot's guide to a stand-alone manual toggle switch operated fan... I know that there's already a tech article on some of the switches you can buy to do it for you, but it seems like everyone wants to do it the toggle switch way.

James