In the process of charging ac I was starting to see progress when the suction line was getting a little cool when everything stopped. vent fan,compressor and electric fans that trigger off of the compressor. The engine fan will still operate normally just not off of the compressor. I looked at AC fuse and it was OK. I jumped low pressure switch in order to charge system. This is also a 12/134a conversion. Help!!!

 

are you sure you checked all of the fuses? i think there is more than one. seems like there is another one comming off of the horn relay that is for the AC system as well.

what were your high and low side pressures when it quit?

did you pull a vacuume on the system first befor charging?

 

I didn't have a hose hooked up to the high side but the low side was around 70 if I remember. I am unfamiliar with 134a but I think it was still alittle low. the compressor was cycling on and off so I don't think I overfilled it. I had it in a long vacuum several months ago but it never would pull down to good. I shot a can or two in it then just to keep moisture out. I was going to charge it and put some dye in it tonight when it went dead. I saw in the owners manual that there is a 30 amp. inline fuse before you get to the blower relay but I can't find it for the life of me.

 

is that 70 on the low side with the compressor running or not running?

with compressor running, the low side should pull down to about 30 on a properly charged 134a conversion.

the compressor was cycling? i thought you said that you jumped the pressure switch. it shouldn't cycle if you do that. it should stay on constant.

on my 73, the inline fuse comes off of the horn relay which is on the drivers side. what year is your vett anyway?

if the vacuum would not pull down too good, then you probably have a leak. leak will let air into the system. air is not nearly as compressable as 134a. this could account for your high reading on the low side. 70 is way too high.

on a fully charged system using 134a with the compresor not running, you would see both the high and low pressures at the same value, around 100 i think. with the compressor running on an 80 degree day, the high side should be about 225 and the low side about 30.

sounds like you are using one of those single hose quickie charge systems. if not, why wouldn't you hook both hoses from your gages up and monitor both high and low pressures?

if you do not have a proper set of AC gages, i would suggest you get some. i'm not 100% sure, but if your low side is reading 70 then you high side reading is probably off of the charts. it may be that your high side pressure got so high that you bogged the compressor down so much that the curent draw from the clutch was enough to blow the in line fuse. that's a very dangerous condition. i'm only guessing here, but extrapolating from the proper pressures and you reading of 70, i would guess that you high side was well above 500. that's dangeroulsy high.

how many cans did you put in it to get a reading of 70?

 

Your right about the pressures. I have been working on a R22 system all day and I guess I got so used to looking at the green scale on the gauges that I didn't think. I was using a good set of gauges but I didn't hook up the high side because as soon as I got it charged I was going to have to pull it right back down to repair the leak. I was wondering why it was cycling with the low pressure switch jumped also. Maybe it was saying " hey stupid, your fixing to blow the clutch off the front of the compressor." It's a 77 by the way.

That was less than 2 cans but it still had a little pressure in it to begin with.

 

good point. must have been the clutch slipping in and out. not the pressure switch doing it's job....

i don't think 2 cans should have gotten you to 70. must be air in the system. you may want to consider replacing your reciever/dryer. don't bother doing it befor you find the leak though.

i would bleed off some of what you have put in there to get your low side pressure down a bit. then you can get a can of dye in there and start leak hunting.

did you find the in line fuse? i'm not sure where it is on a 77. maybe somebody with a 77 factory service manual can chime in to help. take a look by the horn relay though. you never know.....

you'll want to get your compresor working again to make it easier to put the dye into the system.

good luck and i hope this helps.

Mike.

 

Thanks for the info. I can not find that fuse. I have gone through the assembly manual cover to cover. Unless it is above the steering column which I will check with a mirror in a minute I am clueless. What does it look like? I'm thinking it doesn't look like the in-line fuse that I'm used to seeing and I may be overlooking it. I have just had the dash out down to the firewall and some things may not be exactly where they should but I would think it would be in the close proximity.

 

do you have the factory service manual? there should be a chapter in that about AC trouble shooting and repair. in that section there should be a wiring diagram for the AC system. it should even give you the wire colors. you can trace the wire in the diagram in both directions back to what ever they connect to. the other pieces may be eiser to find than the fuse. if you find something that the wire connects to, such as the horn relay in my case, follow the proper colored wire back and you should find your fuse.

im not sure you can get any dye into the system without the compressor running. you are probably stuck untill you find and replace this fuse.

did you check the horn relay for that in line fuse? on my 73, it is an orange wire comming off of the horn relay. about 6" down the wire is a 1/4" diameter by 2" cylinder. the fuse is in there.

a volt meter could also be helpfull in tracking down this fuse.

hope this helps,

Mike.