My cooling fan is not going on. I have juice to the fuse, I tested the coolant temp sensor in hot water with a volt meter and it works and I put direct current to the fan and it works. I suspect its a bad relay. Is there some way to test a relay?

 

Don't mention what year but most have the green/ white as the relay control wire.
Ground that wire / terminal at the relay , key on and the relay should operate

That is only the control side of relay , power to fan through the relay comes from a different source through a fusible link that is not uncommon to blow.
Need to check for 12V at the red or orange wire at the relay connector ( key off )

 

I thought I solved my cooling fan problem which I thought was in the relay. No such luck. Fuse good, temp sensor good, new relay. At 241 no cooling fan coming on. The motor works when I apply juice to it directly. Can anyone tell me where or what the fusable link is on and 84?

 

You need to pull the battery to get to its fusible link.. Disconnect the battery, remove the side panel and slide the battery out. If you look at the + cable you will see the main battery to starter cable and a large red wire, that splits to two fusible links, one for the fan, the other for the fuel pump relay, oil pressure switch and ECM.. If you changed the relay you may have seen the links..

 

Yesterday as I started looking for the fusable link I first started going over the steps i had taken and was looking at some posts from CFI-EFI has posted. I own and FSM and he had posted some pictutres from the cooling section of the manual. Then i saw it THE COOLING FAN SWITCH in side the passanger side head. of the engine. I remember seeing that when I changed the plugs . I always thought it was a emissions sensor. And there it was unpluged. Wow i said my problems are over. So i hooked it up. It had always been there before I saw it a 100 times or more. So I hooked it up and and started up the car and it almost overheated. The fan never came on. I started checking my steps again and boom. The fuse for the cooling fan was blown. I replaced it and everytime I turned the ignation on BOOm the fuse blew. So I disconnected the cooling switch and the fuse did not blow. OK so maybe I have a bad switch and it is shorting out. Then I start thinking what if its not a bad switch and I have a short someplace in the harness. Now I will have a bigger problem. I ordered a new switch but suppose it still blows the fuse. That will mean I have a short and that may be and almost impossible thing to find. So now I want to know if any body makes a cooling fan kit that I can wire from a hot source that would come with a new sensor that would screw into the cooling temp sensor on the intake and that I can then by pass the whole stock system. This might be the better way then trying to find a short in the harness. Any input would be appreciated.

 

Here is the schematic for the 84 fan.. The temp switch is just left of the dipstick and provides the ground to operate the relay. If you are blowing the fuse I would unplug the relay and check voltage at the socket, key on, fuse in.. Not sure if you can pop the cover off the relay to identify the coil terminals or not.. check for voltage on the wire to the switch..

 

Doubtful as it only blow the fuse when you connect the switch.
If you had a short in the wiring from the fuse , through relay to the switch it would blow as soon as you turn the key on

With a good fuse in , key on and the the switch disconnected , touch the switch terminal to ground and see if fan runs.
If it does everything in the system ( fan motor / relay / wiring ) is fine and the fan switch is your problem

 

Easy to check if the fan switch is shorted...just disconnect it and put an ohm meter or continunity checker across the terminals...with the engine cold.

Also FYI...to replace the fan switch requires the coolant level to be lower than the fan switch.

Let me tell you what happens when one tightens the fan switch a bit too much and it breaks off.......get the mop and bucket out!!!

 

Did as you said with a jumper wire into the wire end with switch disconnected key on good ground and boom blew the fuse.

 

I took the old switch out which and yes my garage floor is now full of anto freeze. Thought I had the pan far enough under the car but i thought wrong. Right now that is the lest of my worries. See this car was modfied by the last owner. All 1984s cooling fans are controlled by the switch on the side of the engine blook. The ECM does not have anything to do with turning on the cooling fan. This car has a 8746 ECM which I believe is out of a newer camaro. That may mean I have a problem with the ECM which was wired by hand by the last owner. I think I may be in deep Dodo if the new switch does not turn the fan on at 238.

 

Don't trust your new relay. I had a similar problem, and ended up replacing the relay three times before success. I purchased one from a supplier on this site and one from a local supply store.The two new relays blew the fuse (I cheched them both with a meter and they ccheched ok). Then I had a local Chevrolet dealer do a on line part search on the GM supply system. A OEM relay was found half way accross the country, I contacted that dealership and had them ship the relay. The OEM part worked fine.
I asked why, so I took the case off the original defective relay and I took the cases off the first two replacement relays. I found the aftermarket replacement relays were both constructed completely different from the original relay. I am not saying that this is your problem, I am jist saying that a new replacement parts can be defective, inferior or just not compatible with the early C4s.

 

If grounding the brown wire that goes to the switch blows the fuse, you will do the same thing with it connected to the switch when the motor reaches temp.. As I suggested in post #6 remove the relay and check for voltage at the socket. With key off you should have 12v on the large red wire only. Key on, fuse in, you should have 12v on that red wire plus the dark blue wire which feeds the coil. Also check for voltage on the brown wire s/b 0v.. If all this is true I would ohm check the relay coil..

 

I finally got my cooling fan to work. After replacing the old switch hooking up the OLD relay all is well. I bring this post up again because I believe Jerry make a point that is worth exploring. My cooling fan fuse did not start blowing until I put the new relay in. I think and this is my feeling on this issue that when you go to your local auto parts store and order a 84 relay the part number is the same for 84 and newer c4s. However the 84 is the only C4 where the computer is not involved in turning on the fans. It works from the switch at number 6and 8 cylinder. Maybe more experanced mechanics can comment on this issue but that is what my experance has shown me.