Comp. not cycling, low sd pressure not moving

[scrivyscriv]

Running a '93 2wd Sport with 155k miles. Tried to convert to 134a about a year ago, system had a leak and ran dry earlier in the year. Evap core had a faulty weld, so I replaced it and the dryer. Low side held a charge but stayed at that charge, compressor not cycling. The clutch would only kick in if I tapped the front while it was energized, and would not re-engage without the same.

So I changed the compressor, thinking the clutch was bad. But I still have a similar problem - compressor operated at first on my warm engine, but once it cooled off, the clutch would not energize. Low side still holds a charge. (can't measure hi side with a walmart gage ha)

So yeah... I'll basically have to buy some gages (and bribe the salesman bc I don't have a license to buy it) to further troubleshoot my system, and I don't know if it would be better to let a shop diagnose it and fix the rest myself or buy gages and learn on-the-job.

What's the best thing to do next?

I've searched as many other threads as I can, but "help! a/c probs!" and "explorer air" titles don't help with narrowing down the time-consuming combing thru threads

 

[TheJackal]

So yeah... I'll basically have to buy some gages (and bribe the salesman bc I don't have a license to buy it) to further troubleshoot my system, and I don't know if it would be better to let a shop diagnose it and fix the rest myself or buy gages and learn on-the-job.

You shouldn't need a license to buy a manifold gauge set. I finally got around to getting a set of my own today. Walked into Advance Auto, walked out with gauges. No license here.

 

[Maniak]

I don't know where you are, but Harbor Freight Tools sells a manifold set for cheap.. When on sale they are $32.. When not on sale they are $45..

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92649

~Mark

 

[scrivyscriv]

Moving to electrical troubleshooting

Okay, good deal. I'll pick up the gages once I move past electrical troubleshooting.

Right now I'm changing out the low pressure/comp cycling switch, but here's the deal... It's a converted R-134a system with all original R-12 components, and the replacement switch I'm about to put in is marked "R12." Do I need to replace the drier and switch with 134a parts, or will this R12 switch work? I want a GOOD working system, ha, not an "ok" working system

 

[Cobraguy]

Since you have an R12 designed system converted to R134A, you will never have a GOOD system. R134A is just not as good a refrigerant as R12 and therefore needs different components to operate at an R12 level. But you can still have a system that will get you by.

 

[Maniak]

I don't agree with that... Here in Southern AZ our converted r-12 system can keep the X nice and cold and is more than "just getting us by"

at 2000 rpms On Low fan /Max a/c I can get the temp to the low 30's.. On high fan /max a/c it is sitting in the low 40sF.

I'm using a VOR (variable oriface tube) to help get the temps down at idle and I use a Severe Duty fan clutch (It gets very hot here)..

If you convert the system correctly and replace the bad/marginal parts the r-134 can cool almost if not just as cool as an r-134 system. If you just take your already old/tires r-12 system and convert it then yes, the r-134 won't work as well, but your r-12 wasn't working as well as it could either.

~Mark

 

[Cobraguy]

That is very impressive. But you've hit on the secret. You are more than converting freons, you are replacing system parts that are designed for 134A. Makes a heck of a difference.

By the way, I've had limited success with a VOR. And at $50 a pop or so, you would expect more. So you're happy with them?

 

[Maniak]

Yup.. so far no problems.. I converted to r-134 a while ago.. I'd say at least 150k miles ago..

It did increase my pressure.. enough that when I first installed it and tried to read the pressures (low and high) that I thought something was wrong since my pressures were higher than the shart showed, but I talked to a couple mechanic neighbors and they said it would read higher with the VOR and now I'm just used to it.

When I changed to r-134 I had a noisy compressor and black death (meaning my r-12 system was working poorly).. I flushed the evaporator and then replaced the lines, condensor receiver/dryer and put in a VOR and used r-134.

~Mark

 

[CDW6212R]

Good work Mark, and the higher pressure is a big help with cooling. The higher pressure keeps the compressor from cycling as often. Whenever the AC clutch disengages the cooling stops and allows air temps to go up some. You don't feel that generally, but that's what is happening.

I got tired of my 86 Crown Vic cycling so much(1992) when I swapped in a 302, I disabled the pressure switch. I was delivering mail with it, having the window down I needed cold output. That car went until about 338k before the compressor died, good enough for constant use like older cars.

I like the idea of that VOR (variable orifice tube), I may have to try that sometime. Regards,

 

[Cobraguy]

I haven't noticed much of a difference in pressure with the VOR. But I also haven't noticed a difference in low speed temps either. But I'm also having a problem with the a/c system, so that's not a fair test. I can't get the duct temps below 60 degrees. Yet, I've drilled a very small hole on the downstream side of the evap case in the engine compartment and stuck my thermometer in there and my temps are in the high 30's. So somewhere in that few inches of travel, I'm really warming the air up. Blend door is positively closing off the heater core and I've made sure there is no coolant going to the heater core anyway. It's driving me nuts. The only thing I can figure is the case isn't sealed well and it's drawing in hot engine air. I have Torque Monsters on it and I can't believe they could be creating enough heat to do this. Plus, I've wrapped the case with insulation. What is crazy is my 95 Explorer will run you out of the car the a/c is so cold. It's got 160K on the original system. Every single component in this 99 was replaced when I rebuilt the thing. Go figure. All pressures, everything is working perfectly. Just no cold air at the vents.

CDW...our systems here in AZ don't cycle very much in the heat of the summer. In fact, they may not cycle at all. But in your case, in TN, be careful bypassing the cycle switch. In your humidity, you could freeze the evap and turn it into one big chunk of ice.

 

[CDW6212R]

Well for my mail vehicle anything is fair game, it worked fine for a good four years that way.

My 98 Mountaineer has not been cold for about three years now, and driven little. I haven't swapped the main inside box yet, or the heater control valve. I had the vacuum line plugged, then the vacuum lever tied off, still luke warm air. Mine acts like the airflow is always going through the heater core. I haven't done much testing other than the freon level and the swap of the EATC and blend door actuator. I'd like to track this down soon also.

 

[TheJackal]

That is very impressive. But you've hit on the secret. You are more than converting freons, you are replacing system parts that are designed for 134A. Makes a heck of a difference.

x2 on that retrofit procedure. The air conditioner in an 89 Vic that I once owned was converted from R-12 to R-134a. It cost around $1,000 to do, but when done right it's hard to feel the difference. If you skimp on the retrofit process it's just going to cause you headaches.

Naturally, R-12 is the best refrigerant, but it gets more and more expensive plus if you're not certified it can be very hard to get.

 

[Cobraguy]

Actually Jackal, They haven't made R-12 in years (in the States anyway), so anything you find is left over. I have 3 30 lb bottles left from years ago. I will never sell them as my family still has some old cars and hot rods we own and play with. I want to be able to keep them stock. But I do know that those bottles are worth and I could take a nice vacation on them.

 

[CDW6212R]

Do you mean that I can't get my 91 Mark VII serviced with the good stuff any longer?

 

[Maniak]

You can, but if you find a shop that can still do r-12 (edit: I typed r-134 at first by mistake) its gonna be expensive. When I last looked it was more than $200 for just the r-12 (just freon cost, no labor included) which is why I helped a friend convert his 88 f-150 to r-134.

EDIT: I almost forgot.. some shopt will swear by other r-12 drop in replacements.. likes freeze-12 etc.. Some people love them, other hate them..

~Mark

 

[CDW6212R]

I have a very good AC shop with a great owner who loves high performance and fabrication. He did my 86 Crown Vic in about 2001 for $120 or so, I had lost a clutch and that front seal let the freon go. That was a 54oz. system, with a little extra for my mail route use.

 

[Cobraguy]

Wow! I wouldn't take the cap off one of my bottles for that price!