The AC quit working my my 95 burb last week. The compressor doesn't kick in at all.


Is there a way to jump the compressor? That way I could tell if the compressor is fried or if the system is low on freon.


Any other ideas? Thanks!

On the collector/receiver/dryer there is a low pressure connection.
you can jump it here, but if you have a clogged orafice valve you will hear the compressor screaming in protest and this will make the harmonic pulley fail.
best to put in a fresh valve if you hear any loud groaning after you jump it. also the system will ice up more than before, making it necessary to turn the a/c switch off periodicly to de-ice. I guess the pressure switch controls this function.

I won't jump it for more than a second or two. If it kicks in, then I think it's just low on freon. How long would you have to jump it to hear the groaning?


How do you tell if you have R12 or R134? When did the R134 become OEM?Edited by: w_huisman

More than likely the low pressure switch is bad.
it will groan after a minuite if clogged.
use r134a, everyone should because of cost, put the adapter ports for 134a if pre '96.
Edited by: quantum mechanic

...put the adapter ports for 134a if pre '96...


Huh? http://www.dieselplace.com/forum/smileys/Confused.gif


Thanks QM!Edited by: w_huisman

Jumped the compressor wires. Compressor is fine. Ran for several minutes without a hitch.


How do you determine if it's low on freon or if the low-pressure switch is bad? And how do I determine if I'm running 134 or 12?

Is a Dealer the only place to buy a Switch? I have hunted the Net with no success-- mine works if I give it a "rap" jumper and it works just fine. A Part Number and scource certainl would be appreciated.


Artie in Ct


95' 6.5TD

Just looked under the hood again. It says R134a on a yellow sticker right on top of the dryer!


Not sure where to source a switch, Artie. I'm sure the stealership could line you up with one, but don't know how much $.


Talked to my bro-in-law who runs a mechanic shop. Says he'll fill me back up with r134a for $10/lb, and that I'm likely only a pound or two low.


I always like cheap easy fixes.

I have a hose and guage I bought to fill mine.
I use r134a at 2.50 US a pound from local A/C supply.
I run 45 psi with the compressor running.
pre '96 was r12 but you don't have to use it.
I switched the '93 and '94 first time I had to buy gas.

Before you buy a switch put a set of guages on the system. The age of the truck it is most likely just low on Gas. All Auto AC systems have a slow leak, mostly through the compressor shaft seal. This is just the nature of the Beast so check the system for low Gas before buying any parts.

Be ready: R134a DOES NOT have the capacity that you are used to with R12! It will work, but you may notice a difference in your 'burb. Flare fittings=12 quick connect=134a. Check your pressure while off. If it's at 30 psi with nothing running, you've got a leak. If it's 80 psi and compressor is not running, then your switch is shot.

They switched from R12 to R134A in mid '94


In Wisconsin, you need a liscense to buy or use R134A so I use Envirosafe es12a. Is is much simpler to put in and cools better and at lower pressure.

Give the government an inch, and they take a mile. You find 134a in air horns, and drain blow outs, and all sorts of things that you vent to the atomsphere, and now "oh,no, you may harm the environment if YOU put it in your a/c, and don't have a license" Sorry, I'll get off of my soapbox, I do refrigerantion work, and it just burns my bacon, and I'm vegetiarian at that!

The problem turned out to be the low-pressure switch. My bro-in-law replaced it and (has a nice AC machine at his shop) purged and refilled the system (only 1/2lb low), and it is now blowing colder than ever. He charged me $20.


You gotta like those cheap fixes. http://www.dieselplace.com/forum/smileys/Big Smile.gif

Where did he get the Switch? What did it cost? Always interested in a cheap fix!http://www.dieselplace.com/forum/smileys/Evil%20Smile.gif

My bro-in-law had it laying around in his shop. Someone told me on another board that they're pretty cheap to buy new. I'm sure a dealer could hook you right up.

I've heard of guys running propane in the A/C. Sounds scarry but it cools.

Conversion from R12 to R134 reduces cooling capacity about 15%. Best when converting to get a condensor made for R134.


We have done several Mercedes from R12 to R134 and it always blows warmer with 134 than 12 unless you do a complete conversion and change the condensor. R134 systems usually have a parallel flow condensor.


IMHO, if you have an R12 system, stick with it and repair it: it is a better refrigerant and can be had pretty cheap if you get your own 609 certification for purchasing it (costs $15.00 on-line).

My a/c stopped on my 95 and I suspected the low press switch. when I bypassed it everything worked fine, I've heard from a couple of sources that this switch is notoriously bad, but cheap. The only drag is draining and refilling the system. My truck has 134a from the factory this change happened with the interior change from 94 to 95.

There is a Schrader valve behind the low pressure switch. No need to drain and refill at all!

i've never had to change the switch on my blazer but i used to have an s-10 that had a very similar setup and the switch had a valve under it to keep the system from dumping when the switch was removed. someone here that has done it will know for sure!

There's a needle valve behind the switch. i bought a tool and a few valves at napa and
changed a leaky one on my truck without dumping the gas.

I converted my '94 with the square dash to r134a and
it cool just as good to me and every one whose opinion really count, wife and kids.
I had to put a R134a compressor and reciever dryer.
I also coverted the '93 and eventually had to replace the compresor and receiver.

Hey everyone,


I am new to the forum and new to Diesel Burbs. I have a '95 and the A/C Compressor doesn't kick on. How do I "Jump" the compressor? Also, where is this low preassure switch located?





Thanks

Switch is located in the dryer, the stainless steel colored can on the passenger side fire wall. Pull the plug off the switch and just jump the wires. If the AC kicks on, you're either low on freon or you've got a bad switch.


I just went thru this two weeks ago with my 95 burb. Turned out the switch went bad.

THanks w_huisman. So basically it is the wires that go to the dryer near the top of the canister?.

The wires plug into the switch. The switch is screwed into the canister.


There's only one set of wires that plug into the switch in the dryer, so you can't do it wrong.