A/C Troubleshooting

WyoJeep

WyoJeep

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Nov 10, 2018
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Wyoming
a/c on the fritz. Compressor kicks on and off. Air gets cool but not cold. Recharged it with a DIY kit.
Sits at ~60 psi when the compressor is off, drops to around 45 psi when the compressor comes on (readings based on gauge that came with the recharge kit). a/c lines get nice and cold to the touch, but no cold air in the cab. The refrigerant is in there, but it no worky.
Before I recharged it, it would only get cold when I had it on the "re-circulate" air setting (as opposed to the drawing-in-outside-air setting)...
Also, prior to recharging it, the refrigerant was completely discharged as I had disconnected the a/c lines while working on another project.
Any suggestions which way to chase this problem? :unsure:
 
On mine it was the low pressure / fan cycling switch. About $15. If you get a set of gauges on it, IIRC the manual says it should kick off around 25 psi. Mine was kicking off around 38 and the the compressor wasn't running long enough to do at good.
Edit to add: started with empty charge when I bought it. replaced the dryer and vacuumed the system, new shrader valves and recharge. Happy camper now!
 
No, I didn't do any vacuuming.

Fan cycling switch sounds like a likely culprit. I've been having issues with that as well. It doesn't want to change from one setting to another.

Can you school me on this vacuuming business?
 
You say compressor kicks on and off. Blowing cool engaged warm disengaged right? Not saying it's your culprit but mine was doing the same and I charged and recharged it. turn on would low cold then maybe 10 minutes would go warm and not kick back on till all was cooled down again. Same scenario. Ended up trying the remove a shim from behind comp clutch and I notice on mine it looked like the clutch was engaging partially hi lo spots if you get what I'm saying. Mine had 2 shims 1 maybe a 1/16" and 1- 1/32"-1/64". I removed the thinnest(1/64")and put all back together, turned it on and it's been ice cold since. So I'm assuming a new clutch in is my near future. Actually gets to where I have to turn it down now which is nice because it has been hot as Satan's balls around here past few weeks.

Like I said, don't know if it's maybe your problem but keep it in mind.
 
WyoJeep said:
No, I didn't do any vacuuming.

Fan cycling switch sounds like a likely culprit. I've been having issues with that as well. It doesn't want to change from one setting to another.

Can you school me on this vacuuming business?
Click to expand...
You only apply a vacuum if the system was either completely discharged or opened. The idea is to get all of the regular air, especially the water vapor, out of the tubes so that the refrigerant is more pure and less corrosive. If there was still a partial charge when you refilled it, then the system does not need to be vacuum pumped.
 
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Steel City 06 said:
You only apply a vacuum if the system was either completely discharged or opened. The idea is to get all of the regular air, especially the water vapor, out of the tubes so that the refrigerant is more pure and less corrosive. If there was still a partial charge when you refilled it, then the system does not need to be vacuum pumped.
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I believe the OP had his system opened up if I read his post correctly.

Before driving yourself crazy playing with the clutch and switch get that system sucked down into a vacuum and try recharge it first. Air has absolutely zero benefits to be being in the system. I think harbor freight sells cheap vacuum pumps that should work for the DIY type guy.

Also, @WyoJeep the pressure seems like it could be a bit high. Any chance of you having access to a complete gauge set that shows high side pressure as well?
 
When you were talking about the cycling switch you said it doesn't want to change from one setting to another. Are you referring to fan speed or mode? That won't have anything to do with the low pressure switch
 
@Rollin20z, the compressor kicks on and off at 5-10 second intervals while the a/c is turned on. Seems too frequent to me...

@Steel City 06, I discharged it from the same port that I attempted to recharge it at i.e. the one just to the front of the evaporator on my rig. Then I disconnected both lines at the firewall, and a very small amount of additional refrigerant was released. So I'm guessing that doesn't count as a complete discharge.

@Ct_tj, One of the fan speeds (#2) stopped working some time ago. It didn't really bother me, so I left it alone. More recently the modes have been jacked up, and are more so since I messed with the whole system. Basically it blows from multiple vents no matter what mode it's on. Dash vents = dash & floor, defrost = defroster & dash. Haven't tried floor only lately, but I'm sure it comes out everywhere too.
As for the cooling aspect it was kinda weak before I meddled with it. I knew I'd have the lines disconnected and they'd lose the charge, so I figured it was a good time to recharge it. Now it's still cooler than outside air/fan only, but not by much. It was cooler before.

I've replaced a compressor and evaporator and used a recharge kit before. But that's the limit of my a/c experience.
I'm willing to get whatever tools or parts I need to make it work. (Within reason, of course.) Just need some guidance. Thanks, guys.
 
WyoJeep said:
@Steel City 06, I discharged it from the same port that I attempted to recharge it at i.e. the one just to the front of the evaporator on my rig. Then I disconnected both lines at the firewall, and a very small amount of additional refrigerant was released. So I'm guessing that doesn't count as a complete discharge.



I've replaced a compressor and evaporator and used a recharge kit before. But that's the limit of my a/c experience.
I'm willing to get whatever tools or parts I need to make it work. (Within reason, of course.) Just need some guidance. Thanks, guys.
Click to expand...


Yeah,once you disconnected the lines from firewall you opened up the system to atmosphere air allowing contamination in system. Should definitely be vacuumed down and recharged/oil properly. If not it surely ruin any new parts you have put on it. I'm no ac specialist by any means but that's how I've been taught for forever and a couple sunsets now.
 
WyoJeep said:
No, I didn't do any vacuuming.

Fan cycling switch sounds like a likely culprit. I've been having issues with that as well. It doesn't want to change from one setting to another.

Can you school me on this vacuuming business?
Click to expand...
I'm youtube certified in Hvac!

Moisture is the downfall.

When you opened the lines to the atmosphere you picked up moisture. If its a quick system open/close, hook up to a vacuum pump and pump the system down.

If you left the system open for awhile the receiver/dryer should be replaced.

When you pull a deep vacuum you boil the water out of the system. You can leave the system in a vacuum to see if it leaks.
 
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SOLVED (50%) Had a vacuum drawn and the system recharged by a shop. Cooling properly again. I wanted to do it myself. But it was 107 ° that day, and I sweated out my desire to learn. 😥

Still have the issue with it not wanting to change fan modes properly. Should I be looking at the control switch in the dash as the culprit?
 
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WyoJeep said:
SOLVED (50%) Had a vacuum drawn and the system recharged by a shop. Cooling properly again. I wanted to do it myself. But it was 107 ° that day, and I sweated out my desire to learn. 😥

Still have the issue with it not wanting to change fan modes properly. Should I be looking at the control switch in the dash as the culprit?
Click to expand...
The loss of fan speeds other than the highest setting is usually the blower motor resistor. It’s maybe a $10 part and takes 10 minutes to replace. Easy for the most part.

As for the positions, a little bit of air tends to escape from all vents whenever one position is selected. However, if it’s excessive or there is little or no change, often the vacuum motor that drives the position selector has gone bad, or there is a vacuum leak somewhere. (Note that because the system is driven by the vacuum, the engine must be running in order to change positions.) Changing out the vacuum motor is much more involved than some other projects. Be sure to test for vacuum leaks to eliminate that possibility before tearing apart the dash
 
Steel City 06 said:
The loss of fan speeds other than the highest setting is usually the blower motor resistor. It’s maybe a $10 part and takes 10 minutes to replace. Easy for the most part.

As for the positions, a little bit of air tends to escape from all vents whenever one position is selected. However, if it’s excessive or there is little or no change, often the vacuum motor that drives the position selector has gone bad, or there is a vacuum leak somewhere. (Note that because the system is driven by the vacuum, the engine must be running in order to change positions.) Changing out the vacuum motor is much more involved than some other projects. Be sure to test for vacuum leaks to eliminate that possibility before tearing apart the dash
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I was afraid you'd say that. Every setting is basically 50/50, but I'll just live with it for now. I just got done tearing the dash apart when this all started. Not ready to do it again. But good to know what parts to target when I'm ready.

mrblaine said:
This, so much this.
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The system was initially opened because I was replacing the heater core. I used a walkthrough from the forum, but "You'll need to draw a vacuum on the a/c system after opening it" wasn't included in the directions. I suppose I should go back to the walkthrough and add that tip.

Thanks for your help, everyone.
 
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