Frustrating HVAC fan problems
09-19-2011, 11:13 AM
#1
Melting Slicks
Thread Starter
Frustrating HVAC fan problems
My fan wouldn't work on my '80. Considering the Bubba-effect on some things I found I was not surprised or worried, as simple fixes usually took care of other issues. I checked the fuse in the fuse box and it looked OK, but I replaced it anyway. So...I ran a hot wire to it under the hood. Fan works. Great! So I replaced the relay under the hood on the right side firewall. No love. I checked the resistor set (mounted in the air box near the relay) and it looked good. No burned areas or broken connections. Put it back. Replaced the HVAC controls in the console with new parts as I was going to anyway. STILL no fan. All the wiring looks fine with no breaks or splices. Running out of things to check. Suggestions, please?
09-19-2011, 11:21 AM
#2
Race Director
Member Since: Apr 1999
Location: CORVETTE 77 385 C.I. TEXAS
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Check this:
The only problem I have had was a power wire from the speed switch at underhood connector near pass. rear of ig. shield near firewall. A wire was melted internally at the connector.
The only problem I have had was a power wire from the speed switch at underhood connector near pass. rear of ig. shield near firewall. A wire was melted internally at the connector.
09-19-2011, 09:45 PM
#7
Instructor
I am chasing the exact same problem.
In my car -- there is a brown wire that leaves the fuse block and goes to two places, The switch under the center console and the resister pack in the engine compartment (you can see the brown wire going to the four pin connector. it is the power feed to the fan. I am not getting power to either position. I checked continuity from both locations to the fuze block -- nothing, checked continuity between the two brown wires -- nothing. My only guess is the wire is broken behind the fuze block. I tried to take it off this weekend to see if I could see the broken wire -- no way, the block cannot be moved without moving the entire wire harness, and I figure that will make more damage that I can solve.
Check the power on the brown wire -- if no power, remove the driver side carpet on the center console, you will be able to get to the connector from the side. Any power there? If not, you are in the same place I am. At this point I think I am going to bubba the whole thing, run a wire from the battery (fuzed with a 20 amp fuze) and connect power back to the circuit
Dont know if I helped, but at least you know others are having the same issue -- good luck and let me know if you come up with anything
In my car -- there is a brown wire that leaves the fuse block and goes to two places, The switch under the center console and the resister pack in the engine compartment (you can see the brown wire going to the four pin connector. it is the power feed to the fan. I am not getting power to either position. I checked continuity from both locations to the fuze block -- nothing, checked continuity between the two brown wires -- nothing. My only guess is the wire is broken behind the fuze block. I tried to take it off this weekend to see if I could see the broken wire -- no way, the block cannot be moved without moving the entire wire harness, and I figure that will make more damage that I can solve.
Check the power on the brown wire -- if no power, remove the driver side carpet on the center console, you will be able to get to the connector from the side. Any power there? If not, you are in the same place I am. At this point I think I am going to bubba the whole thing, run a wire from the battery (fuzed with a 20 amp fuze) and connect power back to the circuit
Dont know if I helped, but at least you know others are having the same issue -- good luck and let me know if you come up with anything
09-19-2011, 11:49 PM
#9
Racer
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The blower motor is probably not grounded.
Probe the wires on the resistor pack with your multimeter with fan on low/med. Record voltages on which wire. Then, turn fan on high and probe the top plug on the relay for voltage.
Let us know what you find and we can more than likely tell you the exact problem from this data.
Probe the wires on the resistor pack with your multimeter with fan on low/med. Record voltages on which wire. Then, turn fan on high and probe the top plug on the relay for voltage.
Let us know what you find and we can more than likely tell you the exact problem from this data.
09-20-2011, 07:58 AM
#10
Race Director
The 3 posts above pretty much say it all.
( If your getting power on the brown at the resistor and not on the other wires your going to have to go inside to the yellow between the blower switch and the function control switch.)
An easy way to check the blower motor for ground is to hook your test light up backwards. Attach the alligator clip to a known hot or pos. like the back of the alternator,then touch the probe end to the blower motor case,if the test light lights the case is grounded.
I use this "reverse test light" test a lot on Corvettes.
( If your getting power on the brown at the resistor and not on the other wires your going to have to go inside to the yellow between the blower switch and the function control switch.)
An easy way to check the blower motor for ground is to hook your test light up backwards. Attach the alligator clip to a known hot or pos. like the back of the alternator,then touch the probe end to the blower motor case,if the test light lights the case is grounded.
I use this "reverse test light" test a lot on Corvettes.
09-20-2011, 09:22 AM
#11
Former Vendor
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St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Here is my wire schematic if it helps you
Last edited by Willcox Corvette; 09-20-2011 at 10:25 AM.
09-20-2011, 10:33 AM
#13
Melting Slicks
Thread Starter
The blower motor is grounded. I had connected a power wire directly in place of the existing hot wire on the fan and it worked fine. I'll search our the brown and yellow wires tonight and let you know in the morning.
09-20-2011, 11:36 AM
#14
Race Director
09-20-2011, 08:58 PM
#15
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St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
A simple test would be to up the blower switch in different positions and then test each wire at the resistor to see if you have voltage... Lt. Blue, Tan and Dk Blue.. you should see it move from wire to wire when you change the switch. If you have nothing then it's time to break open the console.
I was in a very long post on this a while back.. I'll see if I can dig up what I posted there.. it's easier than typing it again...
I was in a very long post on this a while back.. I'll see if I can dig up what I posted there.. it's easier than typing it again...
09-21-2011, 01:11 PM
#16
Melting Slicks
Thread Starter
RESOLVED! Thanks for all the help and suggestions! I started by testing the brown wire at the resistance coils. Dead. So i went back under the dash and checked the fuse. Still good. BUT...the contacts for the HVAC fuse were loose on one side causing a slight burned area on the fuse contact. I cleaned up the corrosion from the arcing and then tightened up the contacts with a small screwdriver. Then I installed a new fuse. Voila! The fan now works on all speeds, including low when the key is on. Thanks again!!!
09-21-2011, 11:35 PM
#17
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St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
good deal! Glad to hear it!
Willcox
Willcox