randyp Posted August 4, 2012 Share Posted August 4, 2012 The air quit yesterday on 80 R-model. Disastrous! I tilted hood late in the evening, and checked wire to compressor and it looked ok and was intact on compressor. I could find no pressure switch anywhere under hood, on dryer, near dryer or anywhere. I traced compressor wire to where it goes through grommet in firewall. Grandson got on top of engine and I had him gently push and pull wire while I lay inside in floor looking under dash, (it is cramped too!). Lo and behold, wire had come loose! It is a factory installed Red Dot under dash unit, and i cant for the life of me find where that wire came loose from! Would that wire go to the actual AC switch? There is a switch on front of unit that says heat and AC. Would that wire go to cage motor? Im figuring pressure switch is under the unit somewhere, gonna go back this morning, (didnt have flashlight with me yesterday). Yall gots any ideas? It hit 107 here yesterday. Thanks all,,,randyp Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/ Share on other sites More sharing options...
David Posted August 4, 2012 Share Posted August 4, 2012 Does the wire look original or like an after thought? I've never seen the pressure switch inside the cab. Usually it's close to the dryer. Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132074 Share on other sites More sharing options...
randyp Posted August 4, 2012 Author Share Posted August 4, 2012 Does the wire look original or like an after thought? I've never seen the pressure switch inside the cab. Usually it's close to the dryer.I havent either David. The wire had been spliced into the compressor wire about a foot from compressor. It doesnt look like the original factory wire, but is only wire going to compressor. The dryer is mounted on right side frame rail beside engine, and no switches anywhere. Im guessing pressure switch has to be inside cab with unit or sumpin. It definitely is not anywhere under hood or on outside condenser. Its kinda puzzlin. Thanks, randyp Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132077 Share on other sites More sharing options...
randyp Posted August 4, 2012 Author Share Posted August 4, 2012 Unit still has R-12 in it also David. I checked online and can still get Freeze 12 or 12A as some call it. The understanding i have of it, it is compatible with oil of R-12, and from what i have read, is more efficient than R-134. It is readily available online at reasonable prices. I dont want to convert to 134A, too much trouble and expense. randyp Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132078 Share on other sites More sharing options...
David Posted August 4, 2012 Share Posted August 4, 2012 Some one probably did some "parts changin" and left out the pressure switch. Then just wired it directly to the cab switch. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132079 Share on other sites More sharing options...
randyp Posted August 4, 2012 Author Share Posted August 4, 2012 I bet the farm you are right on that David! Thanks, will let you know what i come up with today. Where do you think that comp. wire will go to in unit in cab? AC switch? randyp Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132082 Share on other sites More sharing options...
David Posted August 4, 2012 Share Posted August 4, 2012 Could pull power from the switch or the fan. Here's a pressure switch pic. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132084 Share on other sites More sharing options...
41chevy Posted August 4, 2012 Share Posted August 4, 2012 Unit still has R-12 in it also David. I checked online and can still get Freeze 12 or 12A as some call it. The understanding i have of it, it is compatible with oil of R-12, and from what i have read, is more efficient than R-134. It is readily available online at reasonable prices. I dont want to convert to 134A, too much trouble and expense. randypFind the contents of the product, some of whats sold on line has propane, acetylene or other explosive gas added. Paul Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132114 Share on other sites More sharing options...
David Posted August 4, 2012 Share Posted August 4, 2012 Find the contents of the product, some of whats sold on line has propane, acetylene or other explosive gas added. PaulThat's interesting. Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132115 Share on other sites More sharing options...
randyp Posted August 4, 2012 Author Share Posted August 4, 2012 Find the contents of the product, some of whats sold on line has propane, acetylene or other explosive gas added. PaulFind the contents of the product, some of whats sold on line has propane, acetylene or other explosive gas added. PaulI dint know that! I dont wanna blow up,,,randyp Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132142 Share on other sites More sharing options...
randyp Posted August 4, 2012 Author Share Posted August 4, 2012 Could pull power from the switch or the fan. Here's a pressure switch pic.Could pull power from the switch or the fan. Here's a pressure switch pic.Thanks David, well, my dryer is plugged off where the pressure switch should be. I dint work on it today, went out to jobsite early this morning with intentions to, got busy motorblading, it got hot, I came home and busted a ice cold watermelon open, now am gonna take a nap like old folks are posed to. randyp Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132144 Share on other sites More sharing options...
randyp Posted August 5, 2012 Author Share Posted August 5, 2012 Well part 2 of this saga. I got up from lil nap, went out to jobsite, found me a small shade tree and parked truck under it and had hood tilted up and scratching my head. The landowner Im working for now lives in Houston, bout 6 hrs. away. He drove in, and after small talk, asked what was wrong with it. I explained it. He asked if I minded him checking it for me. I said no, have at it. He then told me he had been making a living doing air conditioning for the last 30 years. Wow!! He explained where wire went, hooked his gauges to unit, hooked wire up, and all is working fine now! He said I was just a tad low on R-12, but he had bout 100 pounds of it back in Houston and would bring some next week and fix it all up for me. He didnt charge me a dime, wouldnt take anything. He said it wasnt missing a pressure switch, it has the lil probe inside on cooler, and all that controls the compressor. I think he was kinda glad to work on one that old,,80 model. Oboy, Im cool again!!!! randyp 2 Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132195 Share on other sites More sharing options...
David Posted August 5, 2012 Share Posted August 5, 2012 Sometimes you just get lucky. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132213 Share on other sites More sharing options...
DCR Posted August 5, 2012 Share Posted August 5, 2012 To anyone thinking about using R12A Freon - DON'T. I am no expert and only passing on what has been discuss on POG - Prevost Owners Group - recently. This is a very similar internet forum that I belong to but it is about Prevost buses that have been converted to motorhomes instead of Mack trucks. And yes Prevost is also owned by Volvo. Several experts have said what has been talked about in this topic; it is very flamable and is even capable of exploding and they all say do not use it. There are many buses on the road that are still using the R12 and it is a problem trying to get it. Many have had success in finding it on Ebay and many AC shops have been hoarding it It is costly when it is found but in the long run it is still cheaper than converting the entire system to R134 Quote Denny330-550-6020A "Mack Pack" Charter Member Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132227 Share on other sites More sharing options...
randyp Posted August 5, 2012 Author Share Posted August 5, 2012 Sometimes you just get lucky.Sometimes you just get lucky.heh heh,,Yeah, I have medicine i have to take for the other "lucky" moments though. randyp Quote Link to comment https://www.bigmacktrucks.com/topic/26624-compressor-wire/#findComment-132245 Share on other sites More sharing options...
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