>Well, now my dash air conditioning compressor clutch has just stopped
>engaging - no noise, fan still blows, just hot air, blower fuse OK, fan belt
>OK, dash controls all hooked up. Move lever from "air" to "off", top relay on
>firewall clicks, blower stops.
>
>Schematic for '73 shows "a\c ambient sw R.P.O" with wire going to "a/c comp
>cut-off pressure sw RPO", then to "a/c comp & clutch RPO", then to ground.
>Any clues as to where these are located and what they look like??
>
>Also, where is the main ground for the dash electrical? My dash lights are
>acting funny - turning on and off various things make different lights act
>like Christmas tree lights...on, off, bright, dim, etc.
>
>Thanks,
>Lanier
Lanier - sounds to me that you are low on freon. If you look at the
freon hoses that go to and from the airconditioner /heater box under
the passenger front lid, you'll see one hose that leads to an
aluminum tube that has a gauge tap on it and an electrical switch on
the back side. There is a plug with two wires attached that snaps
onto the switch. This is your "cut off pressure switch" or it is
sometimes called the "low pressure cutoff switch". It is on the high
pressure line that comes from the compressor. If your pressure is
too low, caused by a lack of enough freon, this switch shuts off the
clutch so you don't ruin your compressor. It is in series with the
clutch coil.
To test your system remove the plug from the switch and put a jumper
across the two terminals in the plug. A bent piece of wire will work
well. Now, when you have the engine running and you put the air
conditioner lever in the A/C position you should see and hear your
compressor engage. If you look at the receiver/dryer sight glass (in
the top of the little tank that one of the hoses goes to) you might
see bubbles. You might have to clean the dirt off the sight glass
first. Bubbles are an indication of low freon. If you don't see any
bubbles it either means it is full of freon or it means that it is
empty -- all your freon has leaked out. Empty is more likely. Don't
run the compressor too long with the switch bypassed.
When you put freon into your system you jump this switch to get the
compressor to run and then inject freon into the gauge tap on the low
pressure line (the one without the switch) and the compressor will
suck it into the system. Once you have enough freon in the system to
get the pressure up, you can again reconnect the switch and continue
filling while the air conditioner is running until the bubbles just
go away.
It is not uncommon for a system to go down a 12 oz. can a year
without having an apparent leak. However, if your pressure is so low
the clutch doesn't engage you are probably down 1/2 to 2/3 of your
freon or more. In this case you should try to find out if you have a
leak before refilling it as freon is quite expensive now. The
pre-mid 76 systems held 3-1/2 pounds or 56 oz. which is 4-2/3 of the
12 oz. cans. The later systems held 3-3/4 pounds or 5 - 12 oz. cans.
The main ground for the dash board is a wire that attaches to the
upper center of the metal dash panel on the side toward the
windshield. The original is fairly light gauge. I added a heavy
gauge (10 gauge) wire from the back side of the dash and ran it to my
battery ground wire.
Another place where you might have a bad ground is the strap that
goes from the engine to the frame. Actually there are two of these.
The battery ground wire goes from the battery terminal to a bolt on
the lower front passenger side of the engine block. Two braided
metal straps then go from the engine block to the frame. You should
check out all the connections and perhaps disconnect them and clean
them up and you might find that a whole lot of electrical things
begin to work better.
Emery Stora
77 Kingsley
Santa Fe, NM
>engaging - no noise, fan still blows, just hot air, blower fuse OK, fan belt
>OK, dash controls all hooked up. Move lever from "air" to "off", top relay on
>firewall clicks, blower stops.
>
>Schematic for '73 shows "a\c ambient sw R.P.O" with wire going to "a/c comp
>cut-off pressure sw RPO", then to "a/c comp & clutch RPO", then to ground.
>Any clues as to where these are located and what they look like??
>
>Also, where is the main ground for the dash electrical? My dash lights are
>acting funny - turning on and off various things make different lights act
>like Christmas tree lights...on, off, bright, dim, etc.
>
>Thanks,
>Lanier
Lanier - sounds to me that you are low on freon. If you look at the
freon hoses that go to and from the airconditioner /heater box under
the passenger front lid, you'll see one hose that leads to an
aluminum tube that has a gauge tap on it and an electrical switch on
the back side. There is a plug with two wires attached that snaps
onto the switch. This is your "cut off pressure switch" or it is
sometimes called the "low pressure cutoff switch". It is on the high
pressure line that comes from the compressor. If your pressure is
too low, caused by a lack of enough freon, this switch shuts off the
clutch so you don't ruin your compressor. It is in series with the
clutch coil.
To test your system remove the plug from the switch and put a jumper
across the two terminals in the plug. A bent piece of wire will work
well. Now, when you have the engine running and you put the air
conditioner lever in the A/C position you should see and hear your
compressor engage. If you look at the receiver/dryer sight glass (in
the top of the little tank that one of the hoses goes to) you might
see bubbles. You might have to clean the dirt off the sight glass
first. Bubbles are an indication of low freon. If you don't see any
bubbles it either means it is full of freon or it means that it is
empty -- all your freon has leaked out. Empty is more likely. Don't
run the compressor too long with the switch bypassed.
When you put freon into your system you jump this switch to get the
compressor to run and then inject freon into the gauge tap on the low
pressure line (the one without the switch) and the compressor will
suck it into the system. Once you have enough freon in the system to
get the pressure up, you can again reconnect the switch and continue
filling while the air conditioner is running until the bubbles just
go away.
It is not uncommon for a system to go down a 12 oz. can a year
without having an apparent leak. However, if your pressure is so low
the clutch doesn't engage you are probably down 1/2 to 2/3 of your
freon or more. In this case you should try to find out if you have a
leak before refilling it as freon is quite expensive now. The
pre-mid 76 systems held 3-1/2 pounds or 56 oz. which is 4-2/3 of the
12 oz. cans. The later systems held 3-3/4 pounds or 5 - 12 oz. cans.
The main ground for the dash board is a wire that attaches to the
upper center of the metal dash panel on the side toward the
windshield. The original is fairly light gauge. I added a heavy
gauge (10 gauge) wire from the back side of the dash and ran it to my
battery ground wire.
Another place where you might have a bad ground is the strap that
goes from the engine to the frame. Actually there are two of these.
The battery ground wire goes from the battery terminal to a bolt on
the lower front passenger side of the engine block. Two braided
metal straps then go from the engine block to the frame. You should
check out all the connections and perhaps disconnect them and clean
them up and you might find that a whole lot of electrical things
begin to work better.
Emery Stora
77 Kingsley
Santa Fe, NM
solution which was to add an additional 
atrick
