No High with my AC... What is it?

[Evaded]

Been working on my AC, got it all going but have no High? I think its 4 speeds right.. when I try to put it on high it does nothing. AC resistor maybe, or something else? Let me explain better.. when I switch it to high it turns off.

Eric

[bobs409]

I believe there is an inline fuse somewhere that if it blows out, the high speed stops working.

On Chevelles I think it runs across the firewall but not sure where on a truck. Might be the same place.

[jjzepplin]

Just fixed mine from info on this forum. It was a bad connection at the fuse block on the good fuse. Look for the big orange wire coming from your a/c going into the side of your fuse block and then pull the fuse. I just pushed a good fuse onto the bad one and the fan went on. From there I pulled it all out and fixed the issue.

[Tom Vogel]

When one speed doesn't work, it's usually the switch.
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[Wrenchbender Ret]

There is a relay on the engine side around the evaporator unit or firewall. This takes the excessive load of high blower off the ign switch & A/C controls. There is a fuse inline on a heavy gauge wire near this relay. Use a test light to trace it. If the fuse is good the relay is probably bad.

[Evaded]

Ok Ill start checking it all out. Thanks everyone for the info... process of elimination now.

Eric (Evaded)

[Gene]

Originally Posted by Wrenchbender Ret

There is a relay on the engine side around the evaporator unit or firewall. This takes the excessive load of high blower off the ign switch & A/C controls. There is a fuse inline on a heavy gauge wire near this relay. Use a test light to trace it. If the fuse is good the relay is probably bad.

What ^^^ He said

[leddzepp]

The relay is your likely cause. They are not expensive and are easy to replace.
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[70 CST 4X4]

High speed relay

[RenoKeene]

In the cab under the glove box mounted on the ac box.
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[Hutch]

Evaded,
When I had this problem it was the ground wire from the relay on the inside firewall behind the glove box up high on the passenger kick panel side.
You may have to remove the Glove box liner to see this relay
There is a short ground wire with a ring on the end that goes to one of the bolts that hold the inside heater box to the firewall.
Mine had been left disconnected after some heater service
Easy test just run a ground to the frame from the relay while the fan switch is on high
Fan speed symptoms were:
Low =low
Med=Med
High=Very slow

[Evaded]

Thanks Hutch.. made sure that was hooked up when I installed my new duct work for AC and glove box. Will keep eliminating above responses. Thanks everyone so much.

[Andy4639]

I just fixed mine also. I took the switch off and took it a part brushed it real good. Crimped the spade connections really tight with a set of vise grips and put it back together. It's been working ever since.

If the spade connections are loose and wiggle that means heat build up and after a while it want fuction as it should.

[Evaded]

Hmmm... thanks^

[jjzepplin]

So what did the trick...? Inquiring minds want to know!

[1972RedNeck]

When I got my truck the wire was unhooked and hid up in the dash.

[allchevy58]

Mine was the switch.