Cooling fan
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
Cooling fan
Hi Everybody,
I own a 1984 4plus 3 Corvette. I have the diagrams and the shop manual. My problem is this. I changed the relays, CTS and the fan switch. Passenger side of the engine. Oh and the fan motor works. When the car gets to 205 degrees the temperature the switch should turn on at. It blows the cooling fan fuse. No mater how high a fuse I put in, it blows. So how do I find what is pulling the extra voltage?
Thank you
Joe
I own a 1984 4plus 3 Corvette. I have the diagrams and the shop manual. My problem is this. I changed the relays, CTS and the fan switch. Passenger side of the engine. Oh and the fan motor works. When the car gets to 205 degrees the temperature the switch should turn on at. It blows the cooling fan fuse. No mater how high a fuse I put in, it blows. So how do I find what is pulling the extra voltage?
Thank you
Joe
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
Before you changed the coolant fan switch did the fan work?
What fuse is blowing the fan fuse?
Are you using a replacement fan relay? (could be wrong relay)
If the fusible link is blowing can you spin the fan blades manually which would confirm the motor isn't locked up?
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
I can see how the error happens......black ground wire to/in relay circuit with a black w/red stripe as the hot wire to that same relay. If someone did not understand the power/ground design of the C4 electrical system, they'd assume that both of these were grounds,.
To avoid future problems, just remember this. ALL the power wires in a C4 are HOT all the time, some need to have the key ON, others no.
The ground wires are broken and run thru switches, sensors and controls to complete circuits and operate everything.
This is a short sounds like. Installing bigger and bigger fuses is begging for disaster. Wires melt, things start to smoke. Because there is a hot wire that's been tied directly into the ground circuit. I'd guess around the relay,.where the temp sensor completes a GROUND circuit, not a hot.
Where did this number --> 205 degrees come from? 'Cause that's not where the fans SHOULD come on....
That real fan temp is 228. That's where the fans start.
if you installed some aftermarket fan or temp sensor kit, its wired wrong.
Sensors and switches are ground "loops" that jump from one to the next. When the end is reached at a relay or switch its to complete the ground path since the positive path is/was already complete.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
I can see how the error happens......black ground wire to/in relay circuit with a black w/red stripe as the hot wire to that same relay. If someone did not understand the power/ground design of the C4 electrical system, they'd assume that both of these were grounds,.
To avoid future problems, just remember this. ALL the power wires in a C4 are HOT all the time, some need to have the key ON, others no.
The ground wires are broken and run thru switches, sensors and controls to complete circuits and operate everything.
This is a short sounds like. Installing bigger and bigger fuses is begging for disaster. Wires melt, things start to smoke. Because there is a hot wire that's been tied directly into the ground circuit. I'd guess around the relay,.where the temp sensor completes a GROUND circuit, not a hot.
Where did this number --> 205 degrees come from? 'Cause that's not where the fans SHOULD come on....
That real fan temp is 228. That's where the fans start.
if you installed some aftermarket fan or temp sensor kit, its wired wrong.
Sensors and switches are ground "loops" that jump from one to the next. When the end is reached at a relay or switch its to complete the ground path since the positive path is/was already complete.
1) I did not do any rewiring. Last year I noticed that the cooling fan was not cooling. I did some checks and thought it was the fan. I bought a fan and had the same problem.
I replaced the relay on the driver side fender. Finally I hot wired the fan so I can turn it on and off. I just hate having it like this.
You are correct I think it is a short. But how do determine where? Take apart the wiring harness and look for breaks?
205 degrees came from the switch I bought. I am old school and 228 degrees scares me. I will agree that these cars like heat. But, as of now the fan switch is set for 205 degrees. same wiring as the original fan switch.
Just trying to figure out how to find the short.
Thank you. The information you posted may be helpful to me.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
Sounds like a wiring error. Did you do any rewiring?
Before you changed the coolant fan switch did the fan work?
What fuse is blowing the fan fuse?
Are you using a replacement fan relay? (could be wrong relay)
If the fusible link is blowing can you spin the fan blades manually which would confirm the motor isn't locked up?
Before you changed the coolant fan switch did the fan work?
What fuse is blowing the fan fuse?
Are you using a replacement fan relay? (could be wrong relay)
If the fusible link is blowing can you spin the fan blades manually which would confirm the motor isn't locked up?
No the fan did not come on. And I replaced the relay so I bought the fan. Then I realized that the original fan did work and I was blowing fuses.
The fuse blows as soon as the fan starts. I can tell because. When the car hits about 207 the fan moves and then the fuse blows. So it wants to work.
All of the wiring looks original.
I think that this car had an accident. It has headlights from a newer model year 1988. So could a wire have been damaged in the accident. If it happened?
thank you all
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
Okay I am looking at the manual page 8A-149 and it has instructions but, I am at a loss to understand them.
check fuse, okay
voltage to relay I am thinking that the blue wire should have 12 volts from the fuse.
Check relay operation? how do you check it?
Check CTS? how do you check it? bypass the switch?
check fuse, okay
voltage to relay I am thinking that the blue wire should have 12 volts from the fuse.
Check relay operation? how do you check it?
Check CTS? how do you check it? bypass the switch?
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
Okay I am looking at the manual page 8A-149 and it has instructions but, I am at a loss to understand them.
check fuse, okay
voltage to relay I am thinking that the blue wire should have 12 volts from the fuse.
Check relay operation? how do you check it?
Check CTS? how do you check it? bypass the switch?
check fuse, okay
voltage to relay I am thinking that the blue wire should have 12 volts from the fuse.
Check relay operation? how do you check it?
Check CTS? how do you check it? bypass the switch?
I disconnected the relay and jumped the red to the red and black wire. The fan did not run.
Yet I can run a wire from the batter to the fan and it will run.
Any ideas?
thank you all
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
1) I did not do any rewiring. Last year I noticed that the cooling fan was not cooling. I did some checks and thought it was the fan. I bought a fan and had the same problem.
I replaced the relay on the driver side fender. Finally I hot wired the fan so I can turn it on and off. I just hate having it like this.
I replaced the relay on the driver side fender. Finally I hot wired the fan so I can turn it on and off. I just hate having it like this.
You say the cooling fan worked but didn't cool so you replaced the relays and fan motor.
Then you say you installed a lower temperature fan switch and Hot wired it.
Can you explain how you hot wired it and why?
:Have you verified the front of the condenser and radiator aren't clogged with leaves and plastic bags?
Does the wiring at the cooling fan relay look like this where all of
the insulation wiring has shrunk back and could short to each other?
http://i171.photobucket.com/albums/u...elayfaults.jpg
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Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
We have some confusing information here, jseremba. You say the fan starts to spin when the temp hits 205* or so, then the fuse blows. Then you say the fan doesn't run when you connect the red wire to the red/black wire. I don't think this could be true.
I have a 205* CTS in my '84, and mine works just fine.
I'll take a wild guess the relay is wired wrong. Notice the diode in the schematic across the relay coil? In a "normal" relay, it doesn't matter which side of the coil goes to the +12v. In this relay, the cathode of the diode must go to the +12V., or you'll blow the fuse when the CTS closes! Sound familiar?
The relay case probably identifies which terminal is the cathode of the diode. If not, you should be able to measure the low resistance direction of the coil. If in doubt about your measurement, check your meter with another loose diode to identify the cathode.
I have a 205* CTS in my '84, and mine works just fine.
I'll take a wild guess the relay is wired wrong. Notice the diode in the schematic across the relay coil? In a "normal" relay, it doesn't matter which side of the coil goes to the +12v. In this relay, the cathode of the diode must go to the +12V., or you'll blow the fuse when the CTS closes! Sound familiar?
The relay case probably identifies which terminal is the cathode of the diode. If not, you should be able to measure the low resistance direction of the coil. If in doubt about your measurement, check your meter with another loose diode to identify the cathode.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
We have some confusing information here, jseremba. You say the fan starts to spin when the temp hits 205* or so, then the fuse blows. Then you say the fan doesn't run when you connect the red wire to the red/black wire. I don't think this could be true.
I have a 205* CTS in my '84, and mine works just fine.
I'll take a wild guess the relay is wired wrong. Notice the diode in the schematic across the relay coil? In a "normal" relay, it doesn't matter which side of the coil goes to the +12v. In this relay, the cathode of the diode must go to the +12V., or you'll blow the fuse when the CTS closes! Sound familiar?
The relay case probably identifies which terminal is the cathode of the diode. If not, you should be able to measure the low resistance direction of the coil. If in doubt about your measurement, check your meter with another loose diode to identify the cathode.
I have a 205* CTS in my '84, and mine works just fine.
I'll take a wild guess the relay is wired wrong. Notice the diode in the schematic across the relay coil? In a "normal" relay, it doesn't matter which side of the coil goes to the +12v. In this relay, the cathode of the diode must go to the +12V., or you'll blow the fuse when the CTS closes! Sound familiar?
The relay case probably identifies which terminal is the cathode of the diode. If not, you should be able to measure the low resistance direction of the coil. If in doubt about your measurement, check your meter with another loose diode to identify the cathode.
.
Can the relay or connector be the problem? The relay is new. I bought it last year when I first had this problem. The relay has never been used. Can I get a new connector?
Sounds familiar, yes.
My connector is red, blue, white and green, black and red
on the relay is a picture. open switch(red) then a diode (blue and White Green) than a wire (black and Red)
So could the black and red and the red be in the wrong spot?
I have a volt meter so checking the resistance on the cathode is done how? sorry just learning auto electronics.
this is great thank you.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
The Red and the Blk/Red wires are fat wires. They can be reversed, no problem. The Blu and Grn/Wht wires are smaller wires. These must not be reversed. The Red will be "hot" (+12v.) at all times. The Blu will be hot when the key is on, and must be wired to the cathode terminal of the relay coil. If you jumper between the Grn/Wht wire and ground (key on) the fan should run. If you pull the connector off the CTS and jumper that wire to ground (key on), the fan should run. The engine does not need to be running for these tests.
The fan should also run at any time your a/c is on (engine running).
Quote: "I have a volt meter so checking the resistance on the cathode is done how?"
First thing is to learn how your meter works. They're not all the same. With a loose diode, and your meter on 1x resistance (ohms), reverse your test leads to determine if the resistance of the diode is lower with the red wire or the black wire of your meter on the cathode of the diode (the stripe on the diode). Write this down, as it's easy to get confused. Check your relay the same way. Mark the relay to identify the cathode terminal. This terminal must go to the hot wire. (Since your relay has a diode symbol on it, your job is easy!)
The fan should also run at any time your a/c is on (engine running).
Quote: "I have a volt meter so checking the resistance on the cathode is done how?"
First thing is to learn how your meter works. They're not all the same. With a loose diode, and your meter on 1x resistance (ohms), reverse your test leads to determine if the resistance of the diode is lower with the red wire or the black wire of your meter on the cathode of the diode (the stripe on the diode). Write this down, as it's easy to get confused. Check your relay the same way. Mark the relay to identify the cathode terminal. This terminal must go to the hot wire. (Since your relay has a diode symbol on it, your job is easy!)
Last edited by Hot Rod Roy; Jul 13, 2014 at 09:15 PM.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
The Red and the Blk/Red wires are fat wires. They can be reversed, no problem. The Blu and Grn/Wht wires are smaller wires. These must not be reversed. The Red will be "hot" (+12v.) at all times. The Blu will be hot when the key is on, and must be wired to the cathode terminal of the relay coil. If you jumper between the Grn/Wht wire and ground (key on) the fan should run. If you pull the connector off the CTS and jumper that wire to ground (key on), the fan should run. The engine does not need to be running for these tests.
The fan should also run at any time your a/c is on (engine running).
Quote: "I have a volt meter so checking the resistance on the cathode is done how?"
First thing is to learn how your meter works. They're not all the same. With a loose diode, and your meter on 1x resistance (ohms), reverse your test leads to determine if the resistance of the diode is lower with the red wire or the black wire of your meter on the cathode of the diode (the stripe on the diode). Write this down, as it's easy to get confused. Check your relay the same way. Mark the relay to identify the cathode terminal. This terminal must go to the hot wire. (Since your relay has a diode symbol on it, your job is easy!)
The fan should also run at any time your a/c is on (engine running).
Quote: "I have a volt meter so checking the resistance on the cathode is done how?"
First thing is to learn how your meter works. They're not all the same. With a loose diode, and your meter on 1x resistance (ohms), reverse your test leads to determine if the resistance of the diode is lower with the red wire or the black wire of your meter on the cathode of the diode (the stripe on the diode). Write this down, as it's easy to get confused. Check your relay the same way. Mark the relay to identify the cathode terminal. This terminal must go to the hot wire. (Since your relay has a diode symbol on it, your job is easy!)
okay, loose diode does that mean a diode not in a relay? Sorry really crawling when it comes to auto electric.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Hooked on Vettes asked you about the condition of your relay socket. Is it damaged? Unplug the relay and check the resistance between the Blu wire and the Grn/Wht wire at the connector. Should be "infinity".
Verify the Blu wire is hot with key on. (I know this is a repeated test)
Verify cathode terminal marked on the relay goes to same terminal as the Blu wire of the socket. Cathode is the __ end of the mark, not the >, as shown on the schematic.
The "loose diode" test was an attempt to help you understand your meter. Since you have mentioned your relay IS marked, you don't need to do this test.
If all of this checks out okay, your relay is bad.
Last edited by Hot Rod Roy; Jul 14, 2014 at 03:12 PM.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
"Loose": Not confined or restrained; free. Not put up in a container. Readily available. (/Webster)
Hooked on Vettes asked you about the condition of your relay socket. Is it damaged? Unplug the relay and check the resistance between the Blu wire and the Grn/Wht wire at the connector. Should be "infinity".
Verify the Blu wire is hot with key on. (I know this is a repeated test)
I do not care if it is a repeat test. thank you for the help.
Verify cathode terminal marked on the relay goes to same terminal as the Blu wire of the socket. Cathode is the __ end of the mark, not the >, as shown on the schematic.
The "loose diode" test was an attempt to help you understand your meter. Since you have mentioned your relay IS marked, you don't need to do this test.
If all of this checks out okay, your relay is bad.
Hooked on Vettes asked you about the condition of your relay socket. Is it damaged? Unplug the relay and check the resistance between the Blu wire and the Grn/Wht wire at the connector. Should be "infinity".
Verify the Blu wire is hot with key on. (I know this is a repeated test)
I do not care if it is a repeat test. thank you for the help.
Verify cathode terminal marked on the relay goes to same terminal as the Blu wire of the socket. Cathode is the __ end of the mark, not the >, as shown on the schematic.
The "loose diode" test was an attempt to help you understand your meter. Since you have mentioned your relay IS marked, you don't need to do this test.
If all of this checks out okay, your relay is bad.
I thought that the AC had to be charged. but I will check the resistance. The relay is new the connector looks like crap.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
"Loose": Not confined or restrained; free. Not put up in a container. Readily available. (/Webster)
Hooked on Vettes asked you about the condition of your relay socket. Is it damaged? Unplug the relay and check the resistance between the Blu wire and the Grn/Wht wire at the connector. Should be "infinity".
Verify the Blu wire is hot with key on. (I know this is a repeated test)
I do not care if it is a repeat test. thank you for the help.
Verify cathode terminal marked on the relay goes to same terminal as the Blu wire of the socket. Cathode is the __ end of the mark, not the >, as shown on the schematic.
The "loose diode" test was an attempt to help you understand your meter. Since you have mentioned your relay IS marked, you don't need to do this test.
If all of this checks out okay, your relay is bad.
Hooked on Vettes asked you about the condition of your relay socket. Is it damaged? Unplug the relay and check the resistance between the Blu wire and the Grn/Wht wire at the connector. Should be "infinity".
Verify the Blu wire is hot with key on. (I know this is a repeated test)
I do not care if it is a repeat test. thank you for the help.
Verify cathode terminal marked on the relay goes to same terminal as the Blu wire of the socket. Cathode is the __ end of the mark, not the >, as shown on the schematic.
The "loose diode" test was an attempt to help you understand your meter. Since you have mentioned your relay IS marked, you don't need to do this test.
If all of this checks out okay, your relay is bad.
I thought that the AC had to be charged. but I will check the resistance. The relay is new the connector looks like crap.
So I turned on the key and the blue wire was hot.
I took the circuit tested clipped it on ground and then took the probe and put it in the CTS wire. The fan did not start.
I then jumpered the Green/white and blue still no fan.
I turned on the multimeter and set it to Ohms it read one.
When I put the multi meter on the blue and green/white wires it read 1. Is that infinity?
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
Okay I own a dictionary. I wanted to find out was that an auto electronics term. Sorry.
I thought that the AC had to be charged. but I will check the resistance. The relay is new the connector looks like crap.
So I turned on the key and the blue wire was hot.
I took the circuit tested clipped it on ground and then took the probe and put it in the CTS wire. The fan did not start.
I then jumpered the Green/white and blue still no fan.
I turned on the multimeter and set it to Ohms it read one.
When I put the multi meter on the blue and green/white wires it read 1. Is that infinity?
I thought that the AC had to be charged. but I will check the resistance. The relay is new the connector looks like crap.
So I turned on the key and the blue wire was hot.
I took the circuit tested clipped it on ground and then took the probe and put it in the CTS wire. The fan did not start.
I then jumpered the Green/white and blue still no fan.
I turned on the multimeter and set it to Ohms it read one.
When I put the multi meter on the blue and green/white wires it read 1. Is that infinity?
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
okay so decided to see if the wires were crossed I took the blue moved it to the green/white and visa versa. The car got to 205 and the fan did not come on. I then disconnected the relay and jumpered the red/black to the blue and blew the fuse.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Hooked on Vettes identified your problem. How do expect this to work with a melted socket?
Who suggested anything like this???
Yikes!!!
I'm done.
Yikes!!!
I'm done.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
someone also said that if I jumpered the black and red to the blue the fan should run.
And I also tried grounding the CTS wire and the fan did not run. With a new fuse of course.
so how do I determine what is wrong with the blue or cts wire. Are they shorted. The cts wire does not have power.
did not mean to disappoint you all
Race Director
Joined: Aug 2007
Posts: 11,889
Likes: 8
From: Whitefish Falls Ontario
St. Jude Donor '08-'09
the reason I moved the wires was someone suggested they could be crossed. So I tried it.
someone also said that if I jumpered the black and red to the blue the fan should run.
And I also tried grounding the CTS wire and the fan did not run. With a new fuse of course.
so how do I determine what is wrong with the blue or cts wire. Are they shorted. The cts wire does not have power.
did not mean to disappoint you all
someone also said that if I jumpered the black and red to the blue the fan should run.
And I also tried grounding the CTS wire and the fan did not run. With a new fuse of course.
so how do I determine what is wrong with the blue or cts wire. Are they shorted. The cts wire does not have power.
did not mean to disappoint you all
With the switch in run, check for 12 v on the green white wire, this should show the 12v from the blue wire through the relay coil..
Last edited by ccrazor; Jul 16, 2014 at 01:55 AM.