a/c ignorant

[ttpost]

i have never worked on a/c before, so any and all help is appreciated. heres what i got.
hit the a/c button nothing, clutch doesnt engage.

after reading previous posts, i jumpered the low pressure switch and it kicks on, so i figured low refrigerant.

hooked up a gauge after letting it run 3 minutes, on the the low pressure side. i got a reading of 75 #,s (cant remember for sure but it was in the red on the gauge) which is over charged. also when i hooked up the gauge some oily time substance came out, i am not sure if it is freon or compressor oil. the system is not getting cold.
also it hasnt been working for about 2 years.

where should i go next? can i just let out some of the excess pressure? and then add another can of freon? or should i take it to a shop so i dont mess anything up? i would like to figure this out myself. i cant learn if i take it to a shop :rolleyes:

[m-keith]

Perhaps a restriction in the system? What's your high side reading?

[ttpost]

i dont have a high side gauge i will try and get one and check thanks

[taznj63]

With the compressor NOT running, pressure is equal thru the whole system so low side will seem high. Compressor must be running to read low side pressure correctly.
Is your system r-12 or r-134a?
If it is r-134a your local auto store will sell a recharge kit with gauge to recharge your system. If it is r-12 you can buy a kit to change it over for about $40.00 whitch is what I did on my 92. Just have the system vacuum'd out by a local garage then install the fittings from the kit and recharge. I bought mine from Napa and it works great.
Hope this helps...

[odee]

with the vehicle running is the small line out of the back of comp warm or hot? The big line should have some water droplets on it if working right. Pressure seems somewhat high to me for either gas. Might look into it further with a high side reading when running

[norm]

taznj63 is right. (I am HVAC tech) If you put a gauge on low or high side with compressor not running, you will get the same reading relative to ambient temperature (outside air or as affected by engine bay temp.) This would read about 50 psi @ 60 degrees F or 100 psi @ 90 degrees F if R134a. (R12 is different) If your system is near the right charge or over-charged these relationships will work, if too little the psi will be low. (These numbers do not measure the charge, though)
75 psi (before turning on comp.)would be enough to satisfy the low pressure switch (located on the accumulator) and alow comp. to start. If you were getting 75 with running comp. you have trouble - either too much charge, restriction, or other problem. You may have a bad low press. switch if you have 75 before and 40-50 after jumping.
Lots of factors here, but there's $.03 for ya.

[ttpost]

THANKS GUYS. i am going to retest the system, and check my readings again. it is 134 a system. i am now trying to find a high pressure gauge, all i have is low pressure gauge that came with the recharge kit. i will let you know what i find out thanks