A/C Question on 68 c10

[socalkevin68]

Go my A/c charged up...new hoses..and works great..well it did for a day..now it still blows ice cold..but just on lowand medium speed...
My A/C system is all stock 1968..with the R12 in it..
My question is...Does the High Speed on the Fan Switch have a separate resistor?
I looked up some a/c parts in my Classic Parts Catalog and I see a A/C Blower Motor Relay and a Heater A/C blower speed resisitor..could either one of these cause hi speed to go out?
I asked the guy who did my a/c for me and I t hink he wants me to bring it in for him to fix for more money..and to be quite honest i'm beginning to be tapped money wise....i'd like to fix myself if i can...Any help would be appreciated here..
thx
kevin

[john]

Heres a diagram. Hope it helps.

[Andy4639]

Past experance with mine is fan switch will burn up, plastic connection on fan switch will melt and wires want make contact. Check the switch and connections. I redid the spade connections and all has been fine for several years now.

[leddzepp]

Originally Posted by Andy4639

Past experance with mine is fan switch will burn up, plastic connection on fan switch will melt and wires want make contact. Check the switch and connections. I redid the spade connections and all has been fine for several years now.

x 2. This is a very common problem. If all looks well there, I would suspect the relay. Both are inexpensive and easy to replace yourself. No need to take it back to the A/C guy if its blowing cold, he will more than likely charge you an arm (I assume he already charged you a leg the first time)

[socalkevin68]

Originally Posted by leddzepp

x 2. This is a very common problem. If all looks well there, I would suspect the relay. Both are inexpensive and easy to replace yourself. No need to take it back to the A/C guy if its blowing cold, he will more than likely charge you an arm (I assume he already charged you a leg the first time)

Yeah..was kinda hi....being there was nothing wrong with the system...First i
installed a belt...turned ok..then i took to a/c shop...he added freon and oil...and ran it and tested for leaks said all was good..cost me 240 bux...he said "freon aint cheap" ahahhaha oh well..i got a/c now...soon will have high speed i hope

[Hutch]

socalkevin68
Check the ground wire from the relay on the firewall.
It is very short
It is located up high between the glove box and passenger side wall.

There is a short ground wire that is supposed to go one of the shroud bolts that come through the firewall
Easy test is to attach a short piece of wire while it is on high from the relay to ground.

A lot of folks do not get the ground re-attached correctly while working on the heater coil.

The symptoms are
Low= Low
Medium= Medium
High = Very Slow
__________________

[mrein3]

Like others have said, there is a good chance the switch plug is melted from all the current running around back there. Resistors work by turning energy into heat. That heat eventually melts wires.

What I found is that EVERY AC control fan switch plug I found in junk yards was melted so be prepared to purchase a re-pop from LMC or similar.

Then go to NAPA and order a handfull of part number 725147. This is the gold colored wire end that fits in the the switch plug. I keep a little pocket in my connector box full of them because they are used on lots of wires in this vintage of GM vehicle.

Those wire ends, new plug, some yellow, light blue, and dark blue wire and an afternoon of time and you can rehab all those circuts. You should be good to go for another 42 years.

I don't work for LMC or NAPA