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No high speed on fan blower

3673 Views 3 Replies 3 Participants Last post by  T-Man
70 with factory air. I have a low, and a medium speed but no high speed with the heater on. I have changed the high speed relay but that didn't help. I get a feed on the single orange wire when I put the switch in high but the blower stops. The AC compresser is off the car right now. Any ideas what to look for? Thanks.
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You may have gotten a bad relay. Check for power on the purple wire that runs to the blower.

I'm not sure if the 70 is the same, here's how it works on my 68. The Orange wire you're getting power to with your switch on high should be the the smaller 18 gauge wire that runs into the relay. The relay should also have a larger 12 gauge Orange wire with an in-line fuse that gets power from the Horn relay Battery terminal.

When you put the switch in High, power on the small orange wire kicks the relay on to send full power to the Purple wire that goes to the blower motor. When the relay is off, it allows power to go through the resistors from either a Yellow or LtBlue wire for Low and Medium speed.

When you measure power on the Purple wire, the voltage should change as you cycle through Low, Med, and High speed. If you're not getting High, you either have a broken switch that's not sending power to the relay on the 18 gauge orange wire, or your relay is not working.
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