68 Chevelle AC/Heater only works low and high
 

68 El Camino, factory Air and PS. Originally 307 PG car, now 350 with 4L60E.
AC is all factory parts. The only wiring changes I have made is for the HEI distributor, so no wire from starter to distributor to provide 12V. Has full 12V to distributor full time with ignition on.

I am certain I ran into this issue many years ago.
Before I dive in, thought I would post here.

As title says. Low speed works. Hi works. 2 and 3 make no change to blower speed.
There is an orange wire running through the firewall gutter that has been cut and folded back into the gutter.

My first guess is that I need a new rheostat. Anyone deal with this recently?

Thanks in advance.

Yep, fan speed rheostat has failed. Non A/C are easy to change, right on top of the core housing inside the car. No recollection of where they hid it on the A/C housing.

This from a '67, but guessing '68 is similar if not the same.

The a/c rheostat is easy, right up on top. That orange wire in the engine harness powers the blower motor on non-a/c cars, it is typically coiled up and taped to the harness unused.

'68 was a complete redesign of the A/C system and firewall. It does use the same relay and appears to be mounted on/near the housing in this pic.


https://www.yenko.net/forum/cache.ph...2005_p20_l.jpg

I thought I remembered reading something about that in the AIM (also for 69 Camaro with C60). But, I didn't want to ask because it sounded so dumb. Can't believe they didn't just use a different wire harness for AC.

Pretty sure the rheostat is right on top of the suitcase.

This part
 

It should look something like this. Most likely a coil has broken. Let us know.

That's the part. No broken coils, but I am pretty sure it is bad. Found an NOS one on ebay.

Switch is sending juice to the wires as it should.

Missing bracket
 

Also missing one bracket. Goes from the threaded hole on the compressor (circled) to the threaded hole in the bracket on the intake (also circled).

I am sure it is similar to the one on the 67 above. But, mine is a small block.

Anyone have that bracket for a small block 68 vintage.

Do an ohm meter test on the coils before purchasing it, if they carry current, it isn't the problem. There is another switch mounted to the backside of the control panel that is involved in the extra speeds and the relay that Bill has pictured is part of the A/C only blower speed control too.

Came across this link in a search too and is highly regarded for help and parts for A/C.
http://thepartguy.com/mainACPARTS.html