Adding A/C to 1980 Cobra ?

[at_the_junkyard]

Hey Jeff, did some research online and it looks like this orifice tube can be pulled out (of the metal tubing portion on the liquid line) and replaced if necessary.

Would you recommend replacing this while it is apart ?

It does not look like an expensive part but at the same time it may be hard to get out so maybe its not worth it ? My gut feel is not to mess with it unless it was suspected to be plugged or broken etc.

[JACook]

I would pull it out and make sure there's no debris on the screen. But other than that, they really don't ever
go bad.

[at_the_junkyard]

Tried to pull the orifice tube out but did not come easy so I aborted before breaking anything. It looks like the outside of the steel tubing on the hose (about where the orifice should be inside) has crimp marks on it... maybe holding the thing in place ?

Also, do you know at what pressure the AC accumulator switch should open/close at ?

Thanks in advance !!

[JACook]

The crimp area is to prevent the orifice tube from going in too far. Most likely it doesn't want to come out
because the o-rings are stuck to the liquid line. It may come out if you can twist while pulling, but if the
system was otherwise clean, I'm not sure how much I would fight with it.

The LPCO switch is actually adjustable, but typically in an R12 system it will cut the compressor around 30-32
PSI. 30PSI correlates with an evaporator temperature of 32F/0C, and the compressor is cut off to avoid turning
the evaporator into a block of ice. For R134a, the LPCO switch needs to be adjusted down to 27-29 PSI.

[at_the_junkyard]

Hi Jeff,

Its been a while but I finally got everything put back together adding oil along with some new hoses. The system has been holding air pressure at exactly 45psig for over a week now without budging on the guage....so I am quite confident the system is not leaking.

I run tested the compressor by engaging the clutch at idle and it cycled on and off dropping the suction pressure down each time so I am thinking this is working OK as well. Planning to proceed to the next step of vacuum and charge with 12A and see what happens.

I still have some questions about the AC controls and am in need of some expertise. Since the car did not have AC option originally I am starting from scratch and possibly missing some components etc.

Looking at the wiring schematics for 1980 it appears that, in addition to the heater control and accumulator pressure switch, there is also an"ambient temp switch" and a timer relay (engine running?) holding out the clutch circuit. I assume this is necessary to prevent the AC from coming on when its very cold outside or when engine not actually running etc.

I did find and install an electric idle kicker (not sure the schematic term) that engages with the clutch and appears to work but have backed it right off for now. It looks like they do sell the ambient switch at rockauto under AC thermostat ? As far as timer possibly I could do something with oil pressure switch and relay instead.

Thanks in advance if you can help me again.

Todd

[JACook]

The original '80 system had an ambient temperature switch on the radiator support, to disable the A/C
compressor when the outside temperature is below 55F. The '83 orifice tube system uses the LPCO
switch to make sure the evaporator doesn't ice up, so the ambient temparatuere switch is not needed.
I don't believe the '80 V8 system used a compressor relay.

The '83 compressor relay was originally controlled by the WOT switch on the carburetor. The relay has
a 5-second time-delay function, to let the engine settle a bit after start-up before engaging the A/C clutch,
and also to prevent re-energizing the clutch when you're at WOT, and you lift for a shift. All you need to
do is provide switched voltage to one side of the relay coil, and ground to the other, unless you're able to
implement some kind of WOT switch. On the '83, that voltage would have come from Fuse 18, but any
12V source that's active only with the ignition switch in RUN will do. If you didn't get the relay, then
you can just run without it. Only difference is the compressor can stall the engine if it's engaged right
after start-up.

The throttle kicker would have tied into the feed to the LPCO switch, so it boosts idle speed whenever the
system is on, not just when the compressor is engaged.

[at_the_junkyard]

Thanks Jeff,

OK good news about the ambient switch as I did not want to have to mess with one of those.

I don't think I have an AC system relay in the car but not sure where it would reside anyway ? When I traced the 12V wire from the control panel I am pretty sure it went to the open connector near the radiator (assume ambient switch which was not there of course) and then appeared to return back around in the harness by the ignition coil area. So I just spliced this in with the LPCO and ran it to the clutch and kicker for now....so basically comes on when panel switch is "on" and LPCO is "on"

Is the clutch/kicker a heavy load ? (inductive etc) I am thinking in the end I will need to install a 12V relay to control the switching of the clutch (something current rated like a rear defog relay I have spare) I may be able to rig up a micro switch for WOT but I sense from your post that maybe I could live without it...opinion please ?

Still, other than short time delay what prevents the clutch from engaging when the ignition is on, pressure good, but engine is not actually running ? Seems like something you would not want.

Todd

[at_the_junkyard]

OK got the system vacuumed and charged it up and it seems to be working very well.

We have had some warm days up here lately (for Canada eh!!) and it is blowing nice and cold when you crank it up, but also maintains a nice temp once you get going. I have not experienced any problems with idle speed dropping in drive when the compressor kicks in as I thought might happen. Thinking the kicker may not really be needed after all as it idles nicely at about 500 rpm in drive and about 650 in park.

I still need to fix up some of the AC controls wiring but pretty much calling this one a victory all around. Now that I know what to do I would like to upgrade my other Cobra. I have collected some parts and now just need the dash ductwork and controls to fit a 79-86, which is proving to be a tough find. Really lucked out on that 83.

Thanks again Jeff for all your help and expertise on this. I don't think I would have tackled this upgrade if I did not have someone knowledgeable to ask questions.

Cheers,
Todd

[wraithracing]

Congratulations on getting everything working!

I know it was very rewarding and satisfying when I did the same to my 79 PC many years ago!

Trey