MaineJim

Hi all i recently picked up a 1992 LT1 in very good condition,after not having a Vette for thirty years.
Owner said that he had the A/C serviced and changed over to R134A a couple of years back but now it no longer blows cold air.
I got code 09,low refrigerant and thought i would give it a try and recharge it.
I know it should be vacuumed and refilled to be done right but being on fixed income i can't have it proffesionaly done or invest in all the needed tools to do it myself,right now.
So i want to add some refrigerant with oil but the pressure is too low for the compressor to kick in and need to find the A/C clutch relay so i can activate it and fill it.
I just bought the set of factory manuals but they wont be in till sometime next week.
If someone could point me to that A/C clutch relay ,especially a pic of it i would greatly appreciate it.
Any other input on the the subject would be welcome too.
I have done a search here and on youtube but havent found it yet.
Thanks,Jim.

Jalisurr

Don't have a pic, but what you should need to jump is the low pressure switch/sensor, on the low side A/C line. That's the one that will trip if you have low refrigerant levels and prevent the compressor from coming on. Just pull the connector off and jump it with a piece of wire. It'll be up close to the blower motor.

MaineJim

You are right it would be the lower pressure sensor,now to locate it..
Thank you for the input.

pcolt94

If the system is just low on Freon and has not been opened, there is no reason to pull a vacuum on it. As long as you can depress the shredder on the low side for a second and get a hiss, then it has some Freon in it and had not been opened to the atmosphere.

Also, why are you going to add oil with Freon. Too much oil in a system is no good either as it can clog the orifice valve and reduce cooling.
It should have oil in the system already unless you know something different.

Are you using gauges or something on a can to monitor low side side pressure?

MaineJim

Good point on the oil,i will buy a can without and yes i get a hiss from valve so system is not totally empty.
I will use a gauge,a friend has one ,got to find the that sensor now.
Thank you for the input,it is appreciated

raya123_2000

If your getting an error the ECM has turned off power to the circuit and you will need to power cycle the ECM or clear the error. Since your getting the low Freon error put in the leak dye and a can of R134 before you start the car. then put a meat thermometer in one of the air condition vents. Start the car, turn on the air and check the value of the thermometer. The thermometer should read between 55 and 65 degrees depending on the out side air temp. They have the charts on line.

pcolt94

Let me just add the if all electrical is working OK and there was no code 9 by the control head, then closing the low pressure switch should start the compressor.

Running the compressor requires the ECM, programmer, control head, high pressure sensor, cycling switch, relays, wires and connectors. All has to work just to close the A/C relay to start the compressor.

However you had a code 9 which you know is low Freon. But this sets a flag or an inhibit in the programmer and will not send the signal to the ECM to close the A/C relay which goes thru the cycling switch. What this means is you can jump out the cycling switch all day long and the compressor may not start. So to get around this the programmer has to be reset by pulling the fuse (#43 & 18) or taking off the battery lead for a minute. Then if all is working OK the compressor will start

You might have to get some Freon in the system first so the code does not reset.Those are the basics of the system logic and hard to tell you exactly what need to be done but by all means start with gauges and purge them first before connecting to system.

Jalisurr

pcolt94 is on the money, you'll probably need to clear that code before jumping the switch will help.

Here's a pic of the switch on my '90 ZR-1, I assume it's fairly similar on your car. Big ol' thing hanging off the low pressure line close to the firewall on the passenger side. The black plastic part can be pulled off and jumped.

MaineJim

Thank you Pcolt94 for the explaining the system in a concise way and thank you Jalisurr for the pic.
I have done all kinds of work on vehicles and other machinery including electronic work but have never taken the time to learn about A/C systems so now im trying to learn everything about them at once and it's overloading my little brain.
I am trying to learn as much as i can about the new to me Vette and i'll be reading the FSMs cover to cover when they get here.
I know things are not as simple as we might think,just like working with electronics you have to have a grasp on theory and how all those seemingly random pieaces interact with each other.
I was hoping for the easiest quickest way to top off the system before knowing how the whole system works.
I cant stand humidity and after being bone dry for two months we are now in the midst of a three week warm and humid period and it's not fun taking the Vette out.
I have taken it out for only two rides since i got it two weeks ago and before you know it the snow will be flying up here.
Enough rambling,do you guys think the system will take a partial charge without the compressor running?
If it does then i can clear it and try and engage the compressor to finish filling.
Thank you for your help,i'am glad i found this forum.

pcolt94

You can always first try to short the cycling switch connector to see if the compressor will start. The cycling switch is on the back side of the top pipe of the evaporator box. Does not hurt to try.

Basically if the pressure in the Freon can is higher than the pressure in the system, then you will have flow into the system. When you connect the gauges to the car, you will see the static pressure in the system. Depending on ambient temperature, it will probably be in the range of 65 to 100. Usually somewhere in the middle is the norm.

You might try warming the can slightly with some warm water to increase can pressure but don’t go nuts getting it hot. That will give you an edge getting some Freon into the system. If when you open the valve on the gauges and the pressure goes up, that’s a good sign and the flow will be into the car. If the reverse, not a good sign and close the valve but I doubt if you will get into that condition. Knowing the static pressure first will tell you a lot

belairbrian

I had the same problem a few weeks ago with my 92. I used a simpler approach to get the compressor engaged.
You can simply add a jumper from pin "A" to Pin "E" on the clutch relay socket (brown to dk green wires). Just remove the relay and insert the jumper the compressor will engage when the key is in run, even with the A/C off. The relay is mounted to the drivers side wheel well.

Since I have a dual gauge servicing set I hooked it up and connected a can of 134a. Started the car with the jumper in and added some refrigerant. After about 9 or 10 ounces I shut off the car and swapped the relay back in. Finished up the servicing. Now at idle I make around 45 degree air. Once I'm moving it's between 38-40.

pcolt94

There is always many ways to approach any problem. This is good information also just to get the compressor running as Belairbrian described.

Was thinking about this today and if you really want to cheat the system and electronics, disconnect the compressor clutch and run a jumper wire from the battery to the clutch. Make sure you know which wire is ground which may need t be grounded.

This is a good way to go (either method) just so see what you have. If you run the compressor for 30 seconds or so the fat pipes should be getting cold. Having the gauges on the low side will also tell you what the pressures are doing. If there not then that is a sign the Freon is real low and probably needs a can. Do not do more than 1 can at this time, the system only holds 2 pounds total and 1 can is almost half.

If you put Freon in, after that put everything back to normal and see if the system works depending on previous results.

MaineJim

Thank you for the help guys i went the clutch relay way that belairbrian suggested,ran it enough to get about a half a can in,stopped and reconnected it and finished the can.
System works acceptably well for now,thanks a million!