84 model. The car overheated last Friday and I have tried to find out what happened. I had a fan motor that was running whenever the car was turned on. I imagine that it finally failed and the car started to steam.

I have done the tests in the FSM supplement and the fan did not come on. I have replaced the relay and a new fan motor. I have a new coolant temp switch. I am an electrical novice but hopefully I am grounding the temp switch correctly. There is a fusible link near the battery but I'm not sure how to diagnose if it is okay. I am attaching two pictures of the voltage I am seeing at the relay terminal



This is from the FSM wiring diagram that I noted the voltage on each wire.



Not sure of my next move.

 

My first observation: It's not a good idea to just start replacing parts without knowing what the problem is! That will sometimes confuse the issue, as you won't know what's good and what's bad.

That relay connector is toast. If the fan was running all the time, your voltage measurements don't offer a clue as to the reason, so there's no way to answer that question with the information you have provided. Having the fan run all the time will probably cause that connector to fail. Can you post a photo of the relay pins?

Your measurement of 11.4 v. on the grn/wht wire is mysterious, if the voltage on the blu wire is only 0.06 v. That measurement on the blu wire is probably incorrect. It should also be about 11.4 v. If you are connecting the brn wire at the CTS ( Coolant Temp Switch ) to ground, the relay should actuate, and the fan should run.

Your voltage measurement tell me that your fusible link is good.

 

You're right about throwing parts at something Roy, but I've got $30 in what I have so far. Little money and I couldn't figure out what was going on anyway. Doesn't hurt a 35 year old car. I will go ahead and get another connector. I understand what you are saying about grounding the temp wire switch and have tried that several times and suspect I am doing something wrong.

. I have come across three different ways to ground things that will start the fan a moving; grounding the temp switch wire, grounding the drk green wire at the relay connector ( according to the FSM,) and Corvette Ben on youtube says that you can jump the A & B slots on the OBD module. Said that it works on all C4s and it did on one of his cars. Well, guess what onmine.

I am going to investigate some more this morning and see where it goes.

 

Well, Mr. Corvette Ben, it's obvious that you don't know beans about the '84! Wedoo, do you see anything about connections to an "OBD module" (whatever that is), on your FSM diagram?

It appears that you are aware that your CTS for the radiator fan in located between spark plugs 6 & 8 in the RH head in your '84. Later Corvette's are different. What is the part number of your new CTS?

 

The OBD1 terminal for lack of a better term. The CTS is a Master Pro 2-8424. Corvette Ben has a lot of videos and he has a knack of of getting old stuff to run. Has a bunch of Corvettes. But he, along with a lot of people I'm finding, fight the electronics in these cars. Especially the 84s. You replace a part and something weird happens. I read about it all the time.

I have tried to follow every step in diagnosing my issue, even replaced the main components, and it still is not working. My son is graduating from Indiana State this weekend with his masters and I'm going to be busy with that until Sunday; but I will test the continuity in my wires, work to ground the wiring at the CTS and check voltage at the fan connection. Otherwise I guess I'll have to spend the labor rate with my mechanic here in town to see if they can see what I missed.

 

Wedoo, you're being mislead by conflicting information. This circuit is very simple, so there's no reason to let it confuse you. You have the FSM, and it is accurate! Trust it, and don't let Corvette Ben make it seem complex. He says he knows all C4's, then says his idea worked on one! They are not all the same!!! There's lots of bad information on the web.

I have owned my '84 for 15 years, and am pretty good with electrical stuff. The OBD connector (usually called the ALDL connector) is not connected in any way to the radiator fan circuit! After checking your electrical connections with your new connector, and you're still puzzled, report back here. We can help you figure this out!

I can't find any info on your Master Pro 2-8424. I'm using an ACDelco D1855B CTS, and it works perfect.

Congrat's to your son!

 

I checked the voltage at the fuse box and the cfan slot is showing .02 v. I cannot find what the proper voltage should be. Is this my problem, or a problem or nothing to worry about?

 

Please see post #2. You may not be grounding the neg wire of your multimeter properly.

 

What I did is connect both leads to the fuse contact points to get that reading. I did review #2 and you're right, this is a pretty simple circuit but the procedure I am following is not working. I may be grounding things wrong, but since I've never done it before I don't know any better. I have done some research on that and I think I am doing it right. At this point I am thinking about hooking up the fan directly but not sure of any unintended consequences.

Then again would I do that to a 12v wire? I have a connection that goes into a place in the fuse box but not sure where that would go. Looks fairly simple but.... Bu then I may have to take this to someone and learn off of them.

 

Okay, I see the problem. We need to get back to basics. If you'll look at the connections for your battery, you'll notice that the neg ( - ) terminal ( and cable ) connects to the chassis and the engine block. That establishes what's called "ground" in an automobile. ( In Merry Olde England, that's called "earth" which is even more confusing! ) The terminology here, is called "Negative Ground".

In the notes on your diagram, you note "ground to battery". That is correct, and is needed for ALL of your measurements!

To measure "volts", the neg terminal of your multimeter is normally connected to "ground". ( Special situations are different, but let's start with that.) Since we're looking for 12 v. ( because the battery is 12 v. ) Let's look at the voltage on that "cfan" fuse again. The trick on a plastic car is to find a good "ground"! Grounds are always bare metal!!! And some metal parts may not even be connected to that battery ground circuit!!! So, open your hood, then look for a good "ground" connection for the neg terminal of your multimeter, then check your "cfan" fuse again. Ignition switch ON, of course. ( I like to clamp my neg test lead to the hood release cable. ) Anything different than your last test? Turn your ignition OFF and try this test again. Now you've seen how this relay turns the fan off when you turn off the ignition! Look at that diagram again, and I'll bet you can see what I'm talking about!

P.S. NEVER check ohms ( resistance ) on a circuit that has voltage on it!!!

 

Just an update. What I have done is I have hooked up the fan to run all of the time by adding an Add-a-fuse with a toggle switch inside the car. This will be a temporary fix. It seems that the problem is in the cfan fuse the best I can figure out. I can get 12v out of that circuit if I fanangle it but it is apparently loose enough to not be reliable. The Add-a-fuse allows me to run the fan and I placed it in the RRHatch slot and that circuit will work as well.

The car is running at around 190 degrees at operating temperature and that seems to me to be okay. At some point I will pull out the fuse panel and try to repair the cfan terminal (maybe) or let a pro do it. Still looking for the relay connector to replace that. Right now it has been by-passed.

 

I don't think that the slot was overheated, I think that there is a problem with the fuse seating in that slot. I imagine that the connection could be repaired/replaced, but for now I have so many other things to do to the car and I have it fixed temporarily. I am going to go ahead and replace that connector and the relay. I really appreciate the link.

 

It's good to see your update, and that you're able to drive the car! I'm still puzzled about some of your test results. That cfan fuse is only a 3 A circuit, so there shouldn't be any way to overheat that fuse socket, even if the fan was running all the time. Is there a possibility you have a defective fuse? Your test in post #1 said you had 0.06 v, on the dk blu wire, and 11.4 v on the dk grn/wht wire. This is impossible. With a good fuse, you should have about 12 v at the test point in the top of the fuse when the ignition is on. Your bad measurements may be because of your damaged relay connector. Be sure to make good soldered connections to your new relay connector!

Here's a source for that relay connector:
https://www.rockauto.com/en/moreinfo...sn=476&jsn=476

Be sure your relay has a diode in parallel with the relay coil, like this one. This will lengthen the life of your Coolant Temp Switch tremendously!!
ttps://www.rockauto.com/en/moreinfo.php?pk=937980&cc=1041196&jsn=51 9&jsn=519



(Out of sequence. I was still editing.)