Got an 87 with a 2.8. A month ago I heard a binding sort of noise coming from the drivers side hood area. The I noticed car fan had quit working. I got a new fan and checked the fuse under the dash. Hooked up new fan and still not working. Questions.... Is there an under hood fuse somewhere? IS it the relay? How do I check it? where is it? Any advice while I am in the job?

FYI. I have removed AC and the power steering pressure switch.

 

The fan relay is located on the drivers side firewall under the hood. theres 3 relays on mine but i cant remember which one is for the fan. one is fuel pump

 

is there anyway to check the relay?
i dont have ohm meter.

 

does anyone know the wires going into the relay pigtail?

 

The wire you need to look for is a large black one with a red stripe... This one goes to the fan motor. Swap the relay with either one of the others next to it and put the wire in the ALDL as though you're pulling codes. Don't pay any attention to the SES, however, you're testing to see that the radiator fan works when you turn the key on.

 

since i am not running the pressure switches, can I simplify the relay / wiring? Or can I go completely aftermarket with the setup?

 

The pressure switches have NOTHING to do with the fan relay. They tell the ECM when the A/C system is at a certain pressure and to turn on the radiator fan accordingly. There are only 2 switches for the radiator fan... The ECM and the backup fan switch in the back of the passenger's side cylinder head by the lifting eye.

 

OK, so what are the two green wires coming out of the relay? The fan stays on all the time. So I can just get rid of the switches right? well its stayed on when it actully worked.

 

The green wires (actually, the connection at the relay is a splice) go to ground either through the ECM or the backup fan switch to ground the relay coil and turn the relay on to turn on the fan.

The reason your fan is running constantly is probably because you've already cut the connection to the fan switch in the A/C line running down the passenger's side. Those wires need to be tied together OR the blue wire run to a ring terminal attached to ground to turn the fan off. The ECM thinks that the A/C is requesting the fan be turned on, so it's turning the fan on.

 

The pigtail on the relay is really in bad shape anyway to upgrade or simplify the wiring? id like to get rid of the fan switch. Can I just pull it out? and get rid of the two green wires?

 

You can get rid of ONE of the green wires... The one to the fan switch. Everything else stays unless you want to go and get a clutch fan and shroud from an older carbed car.

And you can go out to RadioShack or somewhere and get a universal relay and connector for cheap to replace the $15 relay with a $3 relay. I'm glad I did.

 

I use the generic 4 pin or 5 pin relays off of eBay. Usually 30 amps or better. You can get the nice plugs there cheap too.

 

anyway to check the fan to make sure it works? its new, but you never know...

 

I did both power windows with 2 pairs of them off of eBay... I think I paid $20 for the connectors and 6 relays (2 went into my headlight harness ). I actually used a pair out of an old car security harness for the fuel pump and fan both (both connectors were SHOT). Reason I mentioned RS is because I didn't think he wanted to wait and RS is literally everywhere.

To test the fan, connect the orange wire to the black/red one. And then hook up the ALDL as though you're pulling codes to test the rest of the system (after reconnecting the relay). While the SES blinks, the fan SHOULD run.

 

I think on my cars, the orange is hot all the time. Can't remember for sure, but I was just doing the fan rewiring on both my 89 IROC and my mom's 89 Firebird. One of the wires in that socket was hot at all times in both cars.

The two tests I do on them for functionality are first, I find the hot wire, jumper it to the red/black wire and that should light the fan up directly if the ground to the fan is good and the two wire plug at the fan is good. I've had that fan connector go on me before and if I can't get a good junkyard plug then I put insulated female spade terminals on them. Make sure they are plugged in properly so that the fan spins in the right direction (which is blowing air from the radiator on to the engine block.)

The next test I do is to pull the wire off of the temp sender and jumper it to ground with the key on. That will tell you if the relay is working or not. The last test is just a test drive with the temp switch plugged in so that you can verify when it gets hot that the fan does come on.

Good luck!

 

that is completely over my head....

 

No its not. If you made it here to the forums, then you can do it!

First, you need to go off of a printed schematic. If you are going to keep driving your 3rd gen and want it reliable, then you need this. Start with a repair manual from the auto parts store. You should be able to go into town and get either the Haynes manual or the Chilton's total car care. I buy them used off of eBay, but you need one no matter how you decide to it. Later on you can go back to eBay and buy the GM service manual, but for now, the simple cheapie manual will do what you need.

Your new manual will have wiring schematics in it for most of the circuitry in the car. You will also need a volt meter. Again, if you are new to all of this, just get a cheap one.

Keep in mind that all of the wiring in those parts store manuals may not be noted correctly, depending on the year, but most of them are close. At any rate, if you wire your fan circuit to match the diagram, it will work just fine.

If you go and get your manual, we can easily walk you through the process step by step.

Let us know...

 

i got the generic haynes book. 82-92. i think the pigtail connectors at the relay are toast. and I have hacked out the power steering and ac pressure switches. can you still walk me through? is it possible to get the wiring harness behind the engine out for access?

 

You shouldn't need to get into that harness behind the engine. We should be able to take care of it all from the relay area.

I also had the pigtail problem. On the 89 Firebird it was melted, and on my IROC it was completely chopped out and replaced with lamp cord (long story.) Nothing is as bad as it seems, I promise you.

First step is to get a new relay. You can then wire it up with insulated female spade connectors or get a harness to match it.

Here are some examples from eBay:

http://www.ebay.com/itm/New-12V-DC-4...item2c6ae2ac7c

http://www.ebay.com/itm/2PACK-Car-Au...item416361a5e0

And here is the typical temperature switch that screws into the engine:

http://www.ebay.com/itm/120966205926...84.m1423.l2649

Sometimes you find you need a new temp switch to activate the fan after you have fixed all the other problems.

When you open your manual up to the wiring section, did you find the part that shows your fan and the relay?

 

Looking at my 88 Firebird service manual as a reference, this is what I have:

The main feed of 12 volts is a fat red wire. It comes from the junction block down by the radiator I suppose and is hot at all times. Your first check is to see if you have 12v+ at the red wire. Use the battery negative as your ground for your voltmeter in the beginning to eliminate any other possibilities for now. If you have 12v here, then step one is done.

I am talking about checking wires at your pigtail for the fan relay. Melted or not, the wires should still be able to be accessed with your voltmeter.

 

The next wire to check in your pigtail will be a smaller, brown, wire. It should have 12v with the key in the ON position. This wire gets its power from the C/H FAN fuse (20 AMP)

The fat black/red wire will go from your relay pigtail to the plug on the fan motor. Its the power to the fan and it goes on position B on the plug at the motor itself. The wire on position A at the motor itself is just black and it should be the ground for the fan motor.

The last wire coming off of your fan relay pigtail should be the dark green/white stripe wire. It tees off and goes two directions in your harness. One direction goes to the ECM so that the ECM can ground the relay and turn the fan on based on the fan pressure switch (which you eliminated) or the coolant temp sensor. This sensor is NOT the fan switch that I referenced in an earlier post. This is the sensor that ECM uses from the intake manifold to adjust your fuel settings. It also uses this sensor to calculate when the fan comes on.

This same dark green/white wire tees off and also goes to the temperature SWITCH that is located in either the side of your engine block or cylinder head somewhere. It is used as a last resort if the ECM fails to turn the fan on when the engine gets hot. Keep in mind that this switch will not come on until 220-230 degrees F but that's how our cars are designed.

This dark green/white wire is how I test the rest of the fan circuit, all at once. Once you have your new relay wired in, you can ground the dark green/white wire with the harness plugged into the relay and the key ON, and the fan should come on. If it does, then your wiring is correct. If its correct, then the last thing to verify is that the dark green/white wire does go all the way to the temperature switch so that it can command the fan on when the temperature is hot.

 

ok that helps alot. can i get rid of the ecm wire all together? or does it need to be grounded? id really like to make this circuit as simple as possible with just the fan switch, or a manual switch. after i removed the ac the fan stayed on all the time.

 

You CAN do that, and maybe you should since you eliminated some variables that the ECM needs to evaluate your fan.

If you are going to just run the temperature switch in the block to control the fan, then you need to use a colder temp switch in my opinion.

If you hit the FAQ's at the very beginning of these forums, you should be able to see what the guys here did to run their fans in the best way. I'll see if I can find the link.

Lots of guys here go to the auto parts store and replace their fan switch with the one for a stock 87 Buick Grand National. I think that one turns on between 204 and 214 degrees if I remember...

 

https://www.thirdgen.org/electric_co...pec_mod_single

 

I would love to know how to wire it straight off the engine block. can you find the wiring schem for that? would i still use the stock relay?

 

what about the wire going to the alternator? did i mess up anything there?

 

here is what I would like to do. wire the fan to the engine block switch. my concerns are.....how do I do it? will the ecm be ok with this ground disconnected? what happens to the wire going to the alternator? youve been a huge help. thank you!!!!! maybe you can get this car up and running for me. if all else fails. can I wire the fan straight to the battery?

 

Don't wire the fan straight to the battery.

The ECM is not going to crash without the ground input from the fan. It will be fine.

What wire do you have going to the alternator? There is no wire in your fan relay pigtail that should be going to the alternator. You just need to look at your wires in your pigtail, then make them match your schematic with the above advice from my prior posts.

You should only have orange (12v+ all the time), brown (12v+ with key ON), dark green with white stripe (goes to temp switch on engine block and ECM), and red (goes to fan motor)

Do you have something different?

 

my manual says the brown wire goes to the generator/alternator. s

 

im sorry man. electronics really baffle me.

 

You are looking at the wrong schematic I think.

Find the page that says Coolant Fan _ VIN S

 

Ok, I am looking at my Chilton's manual now, and I see what you are talking about. It shows a parallel brown wire also going to the small brown wire at the alternator. This is an easy check for you.

In your pigtail, you will only have ONE brown wire most likely. But if there are two they are both tied together and going to the same plug. So, when you cut the old pigtail, just make sure both brown wires are still hooked together to the same plug. More likely, you will not see the second brown wire and it is spliced in the harness somewhere. If you do only see one brown wire there is an easy check. First, check that there is 12v+ at your fan relay pigtail with the key ON. Next, unplug the little plug on your alternator and check that pigtail brown wire for 12v+ with the key on. If both places are hot, then your wires are already spliced together.

Let me know what you find.

 

Should be 2 wires at the alternator with 12V key on in the 87... The brown one (constant across years) and a tan/white (comes from instrument panel as a backup and/or feed for idiot light if equipped), on the L (tan/white) and F (brown) terminals at the alternator. Both SHOULD have power with the key on.

The brown wires are spliced in the terminal at the fan relay unless a PO hacked up the wiring. Same as the green wire for the fan switch and ECM control.