air conditioner ?

[rjn72]

My 1987 454 pickup a/c does not work. MY questions are, is there a low pressure cut off switch on these trucks? It has 0 freon in it.The pressure ports have no pressure to them. The a/c compressor does not come on when the a/c is turned on. What would be the first thing you guys would check? Also if I put freeze 12 in it, is it as good as r12 and how many cans should it take. Thanks, Robert

[rwhit57]

The low pressure switch is on the dryer on the passenger side, looks like a sending unit has 2 prongs on it. Pull the plug and use a jumper wire on the plug and see if the compressor comes on and sounds ok. Just for a second, because you don't know the oil content. Then you could try and charge it. It really should have a vacuum pulled on it and checked for leaks, but you can try it. Put a can of oil charge in it and a couple of cans of freon and see what you've got. When the low press. side(big line) condensates it's good.

The freeze 12 works ok but you can run 134 in it. Regardless what some say it won't hurt it.

[cparman]

I agree with RWHIT, IF the system is empty, try to jump the low pressure swith to see if the compressor engages. If it does, I would vacuum the system, and see if it will hold vacuum for 5 minutes or so. If it does, charge the system. I have used freeze12 with good results. Might suggest, working the system for a week or two, to see what happens. Then convert to r134. R12 is hard to find and getting pricy

[rjn72]

Thanks guys, I will try the jumper tomorrow and see if the compressor is engaging. How do you pull a vacuum on the system?

[rwhit57]

You have to have a vacuum pump. If the system hasn't been opened, you can try charging like was mentioned. I have done many that way. As long as the freon doesn't leak out it usually works. Check all the fittings, snug the schrader valves a little. Worst case you lose what you paid for freon, best case you'll have A/C.

[rjn72]

ok, so i tried the jumper on the pressure switch and compressor would not engage. I used a jumper from the battery to the compressor and the clutch engaged. What should I check between the power source and the compressor for my problem? Thanks guys.

[rwhit57]

Did you check the fuse?

[rjn72]

simple things first, lol. I am even an electrician and I haven't checked that yet. Be back shortly.

[rjn72]

Fuse is good. Any other ideas. lol. what is next on the list?

[rwhit57]

Do you have the jumper in the terminal (female side) ? A lot of times that old A/C terminal is junk or the wire frayed,since it lays across the intake it takes some abuse over the years, make sure you don't have power coming through that wire and check the ground also. Next I would say the switch, does the fan come on? If the fan comes on, you could rig a hidden toggle switch under the dash to turn the compr. on/off until you can sort it out. At least that way you could try charging it and see if it's going to hold freon.

[rjn72]

The fan does come on. I am not sure what you mean by a jumper in the female side, The only jumpers I tried were across the low pressure switch and from the battery to the coil on the clutch. I would figure that there is another relay somewhere. But where?The toggle would work, but I would rather find the problem and fix it.

[rwhit57]

Just trying to make sure you understood the where the jumper wire goes for the low pressure switch. To insure we have that correct. You put the jumper between the terminals(2 female spades) in the rubber boot or plug in? Correct?
Then we should have power to the compr. If not you'll just have to trace it back and see where you lose it at.

[rjn72]

got you. Thanks, Let me try again, I may be doing it backwards. In my defense we are having a sleepover at my house tonight and I have a house full of screaming pre teen girls. Yall pray for me lol.

[rjn72]

You got it. I was jumping across the wrong terminal. Sometimes I do things that make me feel awfully dumb. oh well, at least I know. So the pressure switch jumper makes the compressor come on, Would a vaccuum on the system be the next best step to try?

[rwhit57]

Originally Posted by rjn72

got you. Thanks, Let me try again, I may be doing it backwards. In my defense we are having a sleepover at my house tonight and I have a house full of screaming pre teen girls. Yall pray for me lol.

No Problem, It's equally as hard to explain/ understand stuff sometimes just typing it. Good Luck with the kids.

[rwhit57]

Originally Posted by rjn72

You got it. I was jumping across the wrong terminal. Sometimes I do things that make me feel awfully dumb. oh well, at least I know. So the pressure switch jumper makes the compressor come on, Would a vaccuum on the system be the next best step to try?

Rj, First how does the compressor sound? At this point if you have done a good visual insp. of the lines fittings and snugged things down a little, you could try and charge it. By hooking up to the low side(big line) turn compr. on and dump a can of freon w/ oil charge in it, then dump another can of straight freon in it. There you should have some cool air and the compr should run without labor. Try it for a few days and see if it holds it, if it does you could top it off with a partial can until the big line condensates. That is exactly how I just did mine. If it holds a few more days I'm takin it to my buddys shop and vacuuming it and doing it right. Hope I helped you, Randy

[rjn72]

very much so, I am going to order the freeze 12 kit on ebay in the next day or two. It is the cheapest place I have found to get it and it comes with oil and 3 cans of freon and something else, but it also comes with the hose to fill the system which I don't have. Thanks again for the help. The compressor makes less noise than the compressor on my 2003 ford. Go figure. I think it is probably ok, but why would a system be completely empty? Just a general question now, because ac systems are seales, they shouldn't just leak out. My truck sat for 5 yrs or so before I bought it, would that make a difference? The guy I bought it from said "it doesn't work." Never tried to fix it and didn't look into why it didn't work.

[rwhit57]

Ok as a system ages the seals fittings etc detoriate, sometimes they will seep a little or it could be a big leak. Also when an A/C system shuts off it does what is called equalizing, you've probably heard it, it makes a hissing noise. This is the pressure in the system equalizing. So part of the system has more pressure on it in the off mode than it does when it's actually running. I don't know what that Freeze 12 setup is gonna cost ya, but I would bet you can go down to the local parts store and buy a couple of cans of 134(1 oil charge) and a hose for less. That is what I would do, see how it works then go get it done by a pro. Replace the seals, orifice tube,vacuum it, and re-charge. Glad I could help. You're lucky I'm a patient guy, LOL just kidding. Glad to help.

Is that a letter series Chrysler on your avatar?

[gchemist]

Check the high pressure switch too. The sensors are wired in series. I've seen high pressure switches fail. Without turning the engine running, turn the key and A/C on. Jumper the low pressure switch. Check for power at and after the high pressure switch.