Testing radiator fans

The thermo switch closes the contacts on the relay coil (located passenger top side of radiator) which applies power to the fan. So the relay or connections are probably bad.

quote:

Originally posted by DOES 200:
On my red 5S, I noticed it getting close to 200 which it never does, ..

Maybe it is just living up to its license plate.

Yea, connecting the two wires should have turned on the fan. The next culprit might be the relays if you are positive the fuses are good. There is also a possibility that a fan motor is burnt up (happened to me) but it for sure would pop a fuse.

If you have the glass torpedo fuses, test with a meter not just by sight, I had one that looked good through the glass. The filament was broken inside the end caps.

[QUOTE]Originally posted by Dave2811:
Maybe it is just living up to its license plate.

Ha ha, right..."DOES200" is on the group 4, this is the 99PROOF with the problem, so maybe had too many shooters.

I hate getting into that relay box, especially with the car on the upper lift. Is there any testing to try at the fuse panel itself? The fuse doesn't have the glass fuse type, so it was easy to pop it out and look at the fuse itself (bottom two looked real good). I am wondering if maybe a wire came off from the back of the fuse panel.

Good news is that while I was in there, I found the glass fuse to the AC was kaput, so I replaced that and the radio and AC came on

Jan,

Dumb question here, but did you have the key on when you connected the sensor wires together??

John

Hi
Just send "99 Proof" to Oz - I'll sort it out for you

quote:

Originally posted by jb1490:
Jan,

Dumb question here, but did you have the key on when you connected the sensor wires together??

John

Yeah, no dumb question here because it would most likley be me connecting those two sensor wires without the key on. However, in this instance I had the car running when I connected those two wires, and one fan was working fine by the way too. I suppose I could actually try touching a test light to those bottom fuses on the fuse panel, and/or the prongs itself and see what lights up or not. At least then I would know if a wire got disconnected in the back of the fuse panel or something.

Your fastest way to finding the issue is start at the fan and work backwards.

Find the relay that operates that fan. It won't be the one you don't like to access inside the cabin. It should be up front by the light bar. Trace the wires from the temp sender to the relay. Once you find the relay, you could manually trip the relay to see if the fan starts. You could also supply 12v directly to the fan to insure it is working. Let us know if you need more detailed instructions to accomplish these tasks...

Ha ha, slow work in progress. Car is on the upper lift, so I can't get it out in the open right now...too many toys. I was able to climb into the passenger seat though, turn on the key and tested those two bottom fuses and they seemed ok. I got the test light to light up when testing on the fuses and on each side of the prongs. So I figure that area is ok, eh? I tried looking for the relays as well by the radiator & fans, but found none. In that photo at the top, if I take those 2 wires off of the sensor and put a test light between those 2 wires with ingition on, the test light should come on, right? If that is so, I will do that when I get the car down next week.

Shorting the two wires together, should close the relay, and run the fan. If not, then investigate further down the line, ie. the relay, or fan connections....Unless your relays have been removed?!

quote:

Originally posted by RRS1:
Shorting the two wires together, should close the relay, and run the fan. If not, then investigate further down the line, ie. the relay, or fan connections....Unless your relays have been removed?!

I did that previousely connecting the two wires together, but fan didn't run. Trying to eliminate the possibility the fan may be bad too. So, a test light connected between those 2 wires should light up if all the wireing is ok, right?

another option is to disconect the fan wires from the main loom and put 12volts directly to the fan, you will then have no doubt if fan works.

good luck cj

The circuit is not complete unless the relay is pulled in. If the test light close's the circuit/relays then the fan should run. All you are doing is seeing if the thermostat is good, and it probably is. You still need to find your relays, or see if some genius has removed them.

I said weeks ago to start at the fans and work backwards!!! It is a simple matter to apply 12 volts directly to the fan to see if it runs. If is doesn't, you have found your problem. If it does run then trace the wires to the relay...

quote:

Originally posted by ZR1 Pantera:
I said weeks ago to start at the fans and work backwards!!! It is a simple matter to apply 12 volts directly to the fan to see if it runs. If is doesn't, you have found your problem. If it does run then trace the wires to the relay...

Thanks. Car is on my lift, so I could do only so much looking around and test at the fuse box since I could get in the passenger door. Next weekend I will have it down from the lift and can test the fan. I suppose I just hook a wire to the + battery terminal and then touch to the back of the fan wire in?

quote:

I did that previousely connecting the two wires together, but fan didn't run. Trying to eliminate the possibility the fan may be bad too. So, a test light connected between those 2 wires should light up if all the wireing is ok, right?

Maybe. It depends upon the resistance of the coil and the test light, as they would be connected in series. You should get a reading with your test light from one of those wires and ground, but not the other, and the ignition switch needs to be on.

With the ignition switch on, touch those two wires together and then release them. You (or the wife) should be able to hear the relay click. If the relay doesn't click, then there is either a wiring problem, or the relay is bad.

quote:

I suppose I just hook a wire to the + battery terminal and then touch to the back of the fan wire in?

Yes.

John

Was able to work on it a little bit today. In tracing the wires from the fan, I still found no relay. The only thing I found was this funky connection at the bottom of the radiator as shown that connects these two black wires together (sorry bad photo). Not sure what that connector is, or why those two black wires don't connect directly with a male/female conection. As shown in the photo it is disconnected, but I did that myself taking it apart. But anyway, I found this connection was a little loose fitting, so I clamped it down & taped it up to ensure it stays in. Then lowered the car turned the ignition on, and touched the two wires together that go into the the top of radiator sensor, and the fans came on this time. I am not 100% sure that fixed it, but since those two wires at the sensor touched together last time did not start the fan, I figure this may have been it. I could not run the car long since it was late to wake the neithbors, but I will have it out soon and can see if it comes on itself when it gets hot. Thanks for all the diagostic help.

What the heck is that high current diode doing in there? So with the relays removed, the thermostat is carrying the full fan current. Hmmm don't know if they were designed to do that.

That bolt-looking thing is a diode. It prevents voltage from the whirling fans (which become generators after the ignition is off) from keeping the engine running.

That spade terminal is really not intended to connect to the terminal on the top. While you have it out, can you solder a small pigtail with a male spade terminal on it to mate to the black wire?

It seems to me if you had a bad connection there - your fans would not come on.

Rocky

quote:

Originally posted by Rocky:

That spade terminal is really not intended to connect to the terminal on the top. While you have it out, can you solder a small pigtail with a male spade terminal on it to mate to the black wire?

Rocky

These two here connect together. Seens pretty tight now that I clamped it down, but the solder would have been a good idea. As far as a relay, maybe there is one somewhere, but I traced what could see and feel following the wires from the fan but found nothing. But nontheless, maybe it works now.

Thanks guys. Took the car out today round the hood and to the beach, and the second fan came on as it should. Musta been that connection.