AC/Wiring Question(s)
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3rd Gear
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AC/Wiring Question(s)
I have a 1978 SA Corvette, but has AC issues. The fan only runs on low speed. I have put a new relay, resistor, and switch on the car, but nothing has changed. Any thoughts on what my next steps should be? I have read that there is a inline fuse somewhere, but I cannot find it. The wiring seems to be a bit of a mess on this car. I have attached a photo of an orange wire that goes nowhere. It runs along the driver's side fender toward the firewall. Any help on these issues would be greatly appreciated. Too hot in Houston to have no AC. Thanks, Michael
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
This is a pretty simple circuit (the one pictured and the relay are for a late 1979 to 1982, but the circuit is the same, the relay was different for 1978-1979 early.... Orange is your power wire for the high blower only... the other speeds are controlled by the switch in the dash moving power between brown, tan and blue. These wires run to the blower resistor and each wire had a different resistance that slows the motor down. (refer to the chart above and below is where you test.
So a good way to check this would be to remove the connector at the resistor and test for power on the blue, brown and tan wires, then test for power on the orange wire when you have the switch on high blow.
Here is the factory 1978 wire schematic for your heater/ac system.
Post back.
Willcox
Last edited by Willcox Corvette; Jul 7, 2016 at 07:25 PM.
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3rd Gear
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Thank you for the response. This is a little outside my realm so I going to need a little help. How do you check them for power? I watched the Wilcox video on checking the AC switch, and you did a great job of explaining the process step by step. If you could do the same here, then I would greatly appreciate it. Also, do you have any thoughts what the orange wire in the photo plugs into- I cannot figure it out.
Thanks,
Michael
Thanks,
Michael
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Michael.. do you have a multi meter? You'll need one to figure this out. You check for power with this..... You can get a cheap one from Harbor Freight or possibly your local Flaps... (friendly, Local, Auto, Parts, Store)... lol.. The orange wire goes to the high blower relay just as the schematic shows....... But this wire only controls high blow.. and not the other speeds.
Willcox
Willcox
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I measured the voltage on all the wires. Unfortunately, the only one that registers at 12 volts is the low speed wire. Nothing on any other wire. I measured the orange wire at the relay-is this correct? What is my next step? Thanks for the help. Michael
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
If you have power on the brown wire then you've eliminated the fuse as the issue.
So when you switch the blower switch in the second position (number 1 speed) you should have power on tan wire (63 above). And in the next position you should have power on the blue (72 above) at the resistor... the voltage should change wires as you more the blower switch.... If it's not then I'd go into the console and start testing. I'd test the blower switch (there is a video on our tech site for doing this) and then I'd start checking the other wires inside.
The issue could be the a/c switch in the console.. because if you have power on brown, the brown feeds the yellow wire with power through the a/c switch. But you'll just have to dig in and test. Once you have the control out you can test continuity from the blower switch to the resistor too.. (if you don't find the problem).
Willcox
So when you switch the blower switch in the second position (number 1 speed) you should have power on tan wire (63 above). And in the next position you should have power on the blue (72 above) at the resistor... the voltage should change wires as you more the blower switch.... If it's not then I'd go into the console and start testing. I'd test the blower switch (there is a video on our tech site for doing this) and then I'd start checking the other wires inside.
The issue could be the a/c switch in the console.. because if you have power on brown, the brown feeds the yellow wire with power through the a/c switch. But you'll just have to dig in and test. Once you have the control out you can test continuity from the blower switch to the resistor too.. (if you don't find the problem).
Willcox
