Problems with A/C

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SGBARRACUDA

ROY
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I'm working on a 1990 D-150 318 truck. Let me give you a history of what i have done. Today I pulled the freon out of the system and found it over charged. The truck originally held 44 oz. of R-12, it had been converted to R-134 before I got it. Today I installed a new dryer, vacuumed the system and charged it with 80% of the R-12 charge, 35 oz. of R-134. Now the system cools down great but I'm having a problem with the comp. kicking out prematurely. My gauge readings are good 25 low side 200 on the high. I put a test light on the comp. hot wire to see if the clutch coil might be weak, but that is not the case. Vent temp. blows to about 55 degrees but then the comp kicks out. And it seems to not be due to temp. it kicks out at different times. I didn't get to jump the low pressure switch to see if that is the problem. Does anyone have a electrical schematic of the electrical side of my A/C system?
 
Your low pressure looks good and should be cold check your blend door and make sure it is going fully to cold. Your high side is a little high but this is a common problem with ac conversions you may want to consider a more efficient condenser also did you wire in a high pressure cutout switch ?
Brian
 
Given that pressure is nearly equal to temperature in refridgerants,
25 on the low side is too low. Low pressure switch is what is stopping the compumper. Could be nature of the beast with a gas converted system since it doesn't know the gas has changed. Could be the fixed orifice tube is clogged too.
You can add enough gas to keep the low side above 32 and see where the high side goes to. A clean condenser and proper working fan will make a difference there. In the end what I've suggested puts the system charge back to where you started, ( seemingly overcharged ).
 
The R134 requires good evaporator fan speed. Also the adjustment on the thermostatic expansion valve is different. I did a conversion once and was not satisfied, changed to a R134 calibrated expansion valve, it made a huge difference! Also I think parallel flow condensers work better than the serial type.
 
I'm with red fish low pressure switch is cutting the compressor out,Check the components in the system-I may not be right (i do this for a living) but it's not a matter of just replacing the freon because they use different pressure/temps,I would think you would also have to up-date the txv valve and high and low pressure switches to match to new freon--just my 2 cents--Steve
 
You need to add a little more 134 to get the low side to stabilize around 30. 200 at idle on a hot FL day is nothing. When I service my 93 van I converted, I run at Max AC, high fan, and slowly add until suction low side line gets cold. If you add to much, cooling performance will stop and high side will rise really fast. Mopar also uses a temp probe in the evaporator to cycle the compressor, you can pull it out a little to fine tune the cycling. Temp probe works with cold /warm temp selector.
 
Well I tried the more freon route before. Had over 3 lbs 10 oz and the high side went way to high. I'm going to jump the low pressure switch and see if that is what is kicking out the compressor. Maybe tomorrow, it's to damn hot outside now.
 
Not an a/c guy but I have messed with it. Low pressure looks a bit low to me. Last one I messed with I also put a high pressure cut out switch on it. I replaced the condenser with one that had bigger tubes, a/c guy told me to do this when converting. Last thing I did, and it helped a boat load at idle and lower speeds was to put a fan in front of the condenser. I used a Spal. Without vent temp was in the low low 40's (110* outside) with it would blow in the mid-high 20's (110* ambient still)........made that regular cab Ranger like an ice box. Fan was a bit obnoxious noise level wise but.....
 
Update, What a great place this is. I've had two members PM me their phone number to assist me. I've been talking to mderoy340 and with his help I found the evaporator case full of leaves. After I cleaned it out the system works better but I still have an electrical issue. I noticed when I first crank the truck up after sitting overnight, The comp. will not engage for about 5 minutes, then it works pretty good from then on. I need to seal the dang wind leaks in the wing widows, they whistle going down the road. The vent temp. is about 55 degrees. I'm going to call Charrlie_S and see what he thinks, tomorrow.
Stay tuned more to come.
 
Pressure on 134 always runs a good bit higher. I don't know where "the pressure is good" comments are coming from. I've done A/C work since the late 70s. Done literally hundreds of 134 conversions and I always end up with 30-50 on the low side and 300-350 on the high side. I hardly ever pay attention to the amount of refrigerant. I go by the pressure on the gauges and it cools good and works right every time, unless there's another problem somewhere in the system. Also, 134 will never cool like 12 down low at idle. It needs some RPM on the compressor to cool as good as it can. I've seen people complain about new cars regarding that, but there's not a lot you can do. It is what it is.
 
Pressure on 134 always runs a good bit higher. I don't know where "the pressure is good" comments are coming from. I've done A/C work since the late 70s. Done literally hundreds of 134 conversions and I always end up with 30-50 on the low side and 300-350 on the high side. I hardly ever pay attention to the amount of refrigerant. I go by the pressure on the gauges and it cools good and works right every time, unless there's another problem somewhere in the system. Also, 134 will never cool like 12 down low at idle. It needs some RPM on the compressor to cool as good as it can. I've seen people complain about new cars regarding that, but there's not a lot you can do. It is what it is.


I basicaly agree. But feel if the conderser, and air flow are good, once the system stabilizes, the high side should be a fair amount less then 300 psi. Of course ambient temp has a big influence on high pressure.
 
Talked on the phone today to Charrlie S. Great guy and we talked and worked on the A/C in my truck for about 45 min. System is cooling pretty good now blowing down to 45 degrees. I think Charrlie nailed it down to a maginal thermal compressor switch. Now I just need to find one.
 
I'm having trouble locating a A/C clutch cycling switch for my 90 D-150 318 truck. I'm posting a picture of what it looks like, but this one does not fit my truck. Just for reference. Maybe one of you knows or can find who sells one. Thanks

http://www.ebay.com/itm/86-93-Chrysler-Imperial-Dodge-Caravan-Plymouth-Voyager-A-C-Clutch-Switch-35818-/370570319913?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3ADodge&hash=item5647b65829&vxp=mtr


I got mine at the dealership.
If I remember right mine only had a 2 wire connection instead of that 4 wire connector/
I have a 92 diesel and mine would cycle whenever I hit a bump. I actually had to hit a bump to turn it on again:wack:
 
I got mine at the dealership.
If I remember right mine only had a 2 wire connection instead of that 4 wire connector/
I have a 92 diesel and mine would cycle whenever I hit a bump. I actually had to hit a bump to turn it on again:wack:

The one i need is a three wire. But other than that it looks like the one I posted on E-bay.
 
The one i need is a three wire. But other than that it looks like the one I posted on E-bay.


hmm I'll go check mine to make sure it is really a 2 wire connector or a 3, I might have mis- remembered it since it was done a year ago.
 
Mopar had several different thermostat clutch cycling switches.
1) a mechanical two wire
2) a electronic 3 wire
3) a electronic 4 wire.

Within the 3 wire there are different part numbers, depending on the vehicle application.
I have never looked into the differences. It might be the temperature setpoint, or it might be whether it switches, ground or hot, or it could just be the plug connections.
I would just buy the correct switch. But now it seems, like the one he needs is not easily available, but it might be possible to use a 3 wire switch that is for a different vehicle. I need to look into that.
 
Hey Charrlie sorry I missed your call today. I did replace the WOT cut out relay yesterday and i drove it to breakfast this morning. But it does the same thing. I was half way to town before the comp. kicked in.
 
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