a/c airconditioning compressor - not engaging - warm air

[JOHNFAK]

HiBeen playing around with the airconditioning on my truck (as it blows hot air and has done ever since I got it -> but its not been warm enough for me to get on it).Figuring it was low R134a or whatever - got the walmart kit and started filling - problem was it would only allow like 10% of the can to be dumped into the low pressure port/accumulator before it was complaining of too highpressure on the guage. Well I couldn;'t hear the compressor - so after reading around I figured that was it.I climbed under and diconnected the sensor/wiring harness.I then tried to use a piece of wire to bridge the wiring harness - it smoked a little - then nothing.I got my multimeter out and it says no signal. (But I'm figuring there had to be a signal to cause the wire to smoke) ?? So - did I burn something ? More importantnly - have these 2 basic questions 1) How do I run a jumper wire (which I guess needs a 12V supply) to the sensor for the a/c compressor to get it to turn on ? Simply Using a paper clip etc on the sensor end won;t work as their is no power right ? Do I need just 1 wire from the +ve terminal of battery or do I need 2 wires (1 +ve and 1 -ve _ to complete the circuit ?? 2) How do I tell if the wiring harness is burnt or having an issue ? I stick my multimeter in the two connectors - but get 0 signal. Could it be a fuse - which fuse - in cab ? left side of truck where my edge juice is sitting on - or somewhere else in a relay ? Trying to work out if A/C compressor is dead or wiring harness is dead - or fuse - and how to force a 12V signal to the A/C clutch/drive compressor to get it to start circulating so I can fill up with the R134a refrigerant hope that makes sense gonna go get a pic now ......

[Wild and Free]

If it has been dead for a while there will be air and moisture in the system. Throw the walmart low pressure charge system in the garbage and get a pro to vacuum it down and leak check it. Then the dryer will need to be changed out as it filters out moisture and if it was at atmospheric pressure it had moisture in it. The reason it would not take freon was because it had air in the system and there was no room for the freon which is why it needs to be vacuumed down. The only time the elcheapo low pressure charge kits work is if the system has a slooooowwwww leak and still has freon pressure and just needs to be topped off. It will do nothing for a dead system. The reason the compressor would not kick in is because the low pressure switch was not letting the power or ground to get to the clutch due to not enough pressure in the system.

[JOHNFAK]

Inserting pics Shows wire harness and sensor decoupled from A/C compressor

[Wild and Free]

Wow from the pics it looks like you need to fix some oil leaks before you worry about the ac system.

[JOHNFAK]

thanks - yeah I probably will have to

the main thing I wanted to try and check is if the whole A/C is dead (the compressor)

So I was really hoping to see if I can get the compressor to kick on by jumping it - even if for only 10 seconds - so at least they don't try and sell me a $300 A/C unit install if its something simple.

If I have to I will - I am not going to change the a/c myself. BUt a sensor/fuse - I could do that with some help - ha !!

thx man

---------- Post added at 03:15 PM ---------- Previous post was at 03:13 PM ----------

Wow from the pics it looks like you need to fix some oil leaks before you worry about the ac system.

Really - I just thought that was from being a 10yr old truck

She doens't seem to leak that bad (maybe a couple small drops each night)

Not sure whats normal and even how you would fix that without removing the block and cleaning/detailing and checking for seals/wear etc

[Wild and Free]

The switch on the compressor is the high pressure switch and is meant to shut the compressor off at a certain pressure to prevent damage. For testing purposes the switch on the dryer is the low pressure switch which is what supplies the compressor with power or ground if there is enough pressure in the system to do so. generally 10-20 psi switch. You can turn the key on and jump the terminals there to listen if the clutch will engage..........With the engine off of course. If you have checked the fuses and they are good yet then go to the switch and jumper it. I have not looked at a schematic to see how they are wired. Some have power to the compressor and the switch makes the ground and some send power through the low pressure switch. You need to check that with your meter................. NEVER JUMPER TERMINALS UNTIL YOU KNOW WHAT IT DOES AND HOW IT WORKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! As you found out with the smoke signals it sent you. Also after rereading your first post.........NEVER FORCE AN EXTERNAL VOLTAGE TO AN ALREADY LIVE CIRCUIT!!!!!!!!!!!!!!!!! In other words never jumper a circuit with power from another spot like battery or alt ect without knowing exactly what you are hooking into. Your quick and easy ac repair could end up costing you a dead ecm and pcm by jumpering wrong wires and adding power..............

[JOHNFAK]

So your saying this is the wrong switch ? Yeah - I know I shouldn't - but its the only way I can learn ................. don't know any mechanics - I live in and RV and I work in IT - never had a truck before and was never interested. Could change oil and a tire was about it. I try to be careful - and not touch stuff I have no idea about - but between you guys and a couple of people I have bumped into managed to learn a bit ........ maybe just enough to get me in trouble. A lot of forums (various cars) were saying that if the refrigerant gets too low - the switch will turn compressor off so it won't get damaged. As such you can't fill it upwith the R134a stuff as compressor is not on. They said you needed to 'jump' the compressor for like 10 seconds to make sure the compressor is not shot and go from there. thats what I was trying to do ........ thx

[SASQCH]

NEVER JUMPER TERMINALS UNTIL YOU KNOW WHAT IT DOES AND HOW IT WORKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! As you found out with the smoke signals it sent you.

:iagree: Yup, Ya got to keep that magic smoke inside the wires, otherwise things stop working.

[Wild and Free]

So your saying this is the wrong switch ? thx

The one on the compressor is the high pressure switch and you do not need to touch it. the dryer is by the firewall on passenger side and has the low pressure switch in it. the terminals there can be jumpered to see if the clutch will engage but there and there only is it safe to do so. But do not jumper power FROM anywhere just jumper the 2 terminals with a wire in the connector to each other only. On an AC system the low pressure switch makes the circuit and the high pressure switch breaks the circuit. This is only true for this style system as there are other systems that only use low pressure and or high pressure and or thermatic switches ect ect...... But not to confuse I won't go any further into this......

[JOHNFAK]

thanks so anyone got a schematic or diagram showing the 'dryer' and switch that I can safetly 'jump' to check compressor don't want to get the wrong thing again

[Wild and Free]

thanks so anyone got a schematic or diagram showing the 'dryer' and switch that I can safetly 'jump' to check compressor don't want to get the wrong thing again

I already told you where it is and that it is safe to jumper the treminals in it together. It is a black canister about 8 inches long and about 3-4 inches across with 2 pipes coming out of it and the switch directly on top of it mounted to the firewall on the passenger side.

[JOHNFAK]

I already told you where it is and that it is safe to jumper the treminals in it together. It is a black canister about 8 inches long and about 3-4 inches across with 2 pipes coming out of it and the switch directly on top of it mounted to the firewall on the passenger side.

Ok - I call this the accumulator - maybe I was wrong in its naming - hadn't heard the term dryer before - so sorry. Out of curiosity - If I jump the two wires here - how does that kick the compressor on ? And do I jump the switch on top of the canister - or the wiring harness that plugs into the switch ?

[Wild and Free]

Ok - I call this the accumulator - maybe I was wrong in its naming - hadn't heard the term dryer before - so sorry. Out of curiosity - If I jump the two wires here - how does that kick the compressor on ? And do I jump the switch on top of the canister - or the wiring harness that plugs into the switch ?

You are correct in calling it an accumulator as it accumulates debris and moisture, I am old school and have always called it a dryer from the older systems. Some systems have an accumulator and a dryer to make things even more complicated. You jumper the wires of the wiring harness together after you disconnect it from the low pressure switch on the accumulator. As I stated before it will either make a ground so the clutch will engage or it will send 12 v+ to the compressor depending on the system. The low pressure switch is the on - off switch for the AC system and the high pressure switch is the "Breaker" so to speak.

[JOHNFAK]

okthanks - I have 12V (tested with multimeter) comming from the wiring harness that plugs into the accumulator/dryer. I tried to jump it by closing the circuit - and nothing happened.So - thinking I either have a dead compressor - or a fuse issue. The only fuse I could find was a fuse relay for the A/C Clutch on drivers side fuse panel under hood near battery. Not sure what to do with this ?? Let me know if any other ideas - I am gonna ping a guy that helped me out once and see if I can pay him to help me on a few things with the truck - and learn a little - but not sure if he has the time. thx again

[Wild and Free]

Did you plug the other switch back in before trying to jumper it? If there was power to the low pr sw then the fuse is good but you could try and switch one relay with another and retry as most of the relays are the same..Plug and play there.

[JOHNFAK]

Did you plug the other switch back in before trying to jumper it? If there was power to the low pr sw then the fuse is good but you could try and switch one relay with another and retry as most of the relays are the same..Plug and play there.

Yes plugged back in But there is no voltage in that part of the wire harness - wondering if I shorted it when I tried to jump it with the smoke - hence thinking maybe a fuse now - then back to jumping the accumulator/dryer switch ?

[Mopar1973Man]

Here you go... All the wiring for the A/C...

[JOHNFAK]

Here you go... All the wiring for the A/C...

mwaaaaa - can I have the non-chinese version ??? ok - I get the point ........................ trust me I am as frustrated trying to work it out as your guys are trying to explain it to me ........ will find another way thx anyway

[Mopar1973Man]

Try again... Sorry the print is so small butr after the site render it it shrinks...

[JOHNFAK]

Try again... Sorry the print is so small butr after the site render it it shrinks...

Haha michael - no sorry - my bad I meant - I can't even jump an a/c compressor with all the help here from the guys :banghead: and now you send me a wiring diagram I don't even know how to 'partly' read it Hence the 'chinese' reference. A little frustrated - so hope thats not comming across - as I know this stuff is grade 2 for you guys :| Heck - It took me 2 hours before I started the thread to work out where the a/c compressor was - I thought the compressor was the accumulator/dryer : ) I managed to work that one out eventually (couldn't find it in 2001 service manuals or chiltons - I guess they considered too basic also) by looking at pics on ebay of what an dodge ram a/c compressor looked like - then I realized it wasn't the accumulator. anyway - am sure somewhere I will work it out ..............