AC cools BETTER when idling??

Status
Not open for further replies.
E

exranger06

Joined
Jan 25, 2008
Messages
4,464
Location
Guilford, CT
2006 Ranger- This truck always had the best AC I have ever experienced in any vehicle. It would always get down to 38 degrees and make me shiver within a few minutes of turning it on. Then I got into an accident and had to get the condenser replaced. I got the truck back from the body shop in the middle of winter, so it wasn't until a few weeks ago that I noticed the shop severely under-charged the system. So I add some more refrigerant until I get vent temps of about 38 degrees. Perfect. But when driving down the highway, the vent temps never get below 47 degrees. As soon as I park it in the driveway and leave it idling, the temp drops to about 38.

I would understand if it cooled ok when driving and not as much when idling, but the exact opposite is happening. I'm pretty puzzled.
 
How did you know it's under-charged? You just added refrigerant until the vent temps arrived at a certain point?

Put it on gauges. It's probably over-charged.
 
I have a gauge set and the pressures were perfect. I don't remember the exact numbers, but it definitely wasn't overcharged.

When it was under-charged, the vent temps were around 58 degrees, the compressor was cycling every 10 seconds, and the pressures were way too low.
 
Did the body shop get all the seals and ducting around the condenser back on properly? You may have an airflow problem? I'm a GM guy. Does this truck use electric cooling fans? Maybe they're not hooked up properly.
 
Nope, it has a mechanical fan. I know all the ducting and whatnot was reinstalled. One of the pieces was actually on back-order, so the body guy had me bring the truck back when it came in so he could reinstall it. I didn't even notice anything was missing. He really didn't miss anything.
 
The heater control valve is letting hot coolant into the heater core. Theres not much water pressure @ idle vs the amount of water pressure when driving it.

Try feeling the heater hoses near the heater core while revving it up. They should be cold. Any heat in them will affect the outlet temp.

Or just pinch them off making sure that they are completly closed off and drive it.
 
You have gauges. That's excellent! I'm going to assume you read them both at idle and also at RPMs equivalent to highway speed but didn't take readings while actually driving. Get readings at highway speed and also take temp readings at idle, stopped but elevated RPMs, and at speed. Let us know what you've got. That's 9 numbers we're looking for. If you look at those numbers and figure it out immediately, let us know anyway.

Keep in mind that even if your body shop is good enough to make sure all air deflector are in place, they might not notice a hidden kinked line. If this is an insurance job they probably used the cheapest available part for everything. The condenser might even be (yeah this actually happens) painted! Fitment of el-cheapo parts may not be very good. If they're sloppy enough with mechanicals to send the truck out with AC undercharged they very likely didn't flush it out (bad practice for for TEV or orifice health) and can't possibly be sure of lubricant volume. Do you know any of determining the total volume of refrigerant in a repaired AC system without flushing it and replacing the dryer? You don't know how good their vacuum pump is.
 
Originally Posted By: Chris142
The heater control valve is letting hot coolant into the heater core. Theres not much water pressure @ idle vs the amount of water pressure when driving it.

Try feeling the heater hoses near the heater core while revving it up. They should be cold. Any heat in them will affect the outlet temp.

Or just pinch them off making sure that they are completly closed off and drive it.





+1
 
UPDATE: So I finally got around to taking some more readings. I’m beginning to think it actually is a little overcharged. Ambient temp was about 70 degrees. At idle, I was getting a vent temp of 41.9 degrees. The high side pressure was 175 psi and low side was 26 psi. After letting it idle for a little while longer, the temp dropped further to 40.8 degrees and the high side pressure was 140 and low side was 23 psi.

Then I revved it up to around 2000 rpm and the high side pressure rose to 225 psi and low side pressure dropped to 20 psi, at which point the low pressure switch tripped and turned the compressor off. When the low side pressure rose back up to about 40 psi, the compressor turned back on and basically repeated the cycle again. The second time I revved it up the high side pressure rose to about 275 psi before the low pressure switch tripped again. When I revved it up, the vent temp rose to about 43 degrees. I would imagine that it probably would have rose to about 48 if I continued revving it.
 
You need an additional big fan going when testing AC pressures and sitting still.
Measure the ambient temp an inch in front of the condenser.

You may have water in the system and it is freezing, blocking flow.
 
I'm considering just starting fresh by having the system evacuated, replacing the orifice tube and accumulator, putting fresh oil in, and vacuuming the system down and recharging it. If you want something done right, you gotta do it yourself...
 
UPDATE: I FINALLY got around to working on this. I took it to a shop to get the system evacuated, and they said it STILL only had about half a charge in it. Yesterday I removed the accumulator (will not install the new one until I'm about to vacuum and charge the system) and replaced the orifice tube. I was going to remove the compressor to drain the oil out of it, but it's kind of stuck and too much of a hassle. It doesn't sound like there's much oil in it anyway. I did however drop the bolt that bolts the lines to the compressor and can't find it.
mad.gif
So that put me at a stand-still for the rest of the day. I will update again when I'm finished.
 
That sounds right after your last post I was going to say the pressures were a little low.
 
Another small update: I finally found that bolt, and I managed to remove the compressor and drain the oil from it. Everything is still taken apart right now.
 
Added fresh oil to the compressor and reinstalled it. I went to install the new accumulator, and the ridiculously soft metal threads stripped
mad.gif
. I ordered a Motorcraft off Rock Auto. It should be here Wednesday. I'm just mad that I added hygroscopic PAG oil to the compressor and now I have to leave the lines disconnected for a few days. I put plastic over the ends and taped them up real well. This thing just keeps kicking me in the balls every step of the way...
 
I would think it was normal to have a higher vent temp while driving vs idle. While driving air would be rammed into your vents, causing increased temps. The cabin is never air tight on purpose. There is some outside venting even on recirc.
 
Originally Posted By: LeakySeals
I would think it was normal to have a higher vent temp while driving vs idle. While driving air would be rammed into your vents, causing increased temps. The cabin is never air tight on purpose. There is some outside venting even on recirc.

All I know is it doesn't work nearly as well as it did before the accident. All I want is for it to work like before.
 
Don't blame you. Its not uncommon for things to be knocked off on impact, check and make sure all the ducts are connected, and the vents actually close to outside air.
 
Status
Not open for further replies.

Similar threads

F
03 Suburban AC Issues - Diagnostic Challenge for Intermittent Performance
2
Replies
25
Views
2K
wlk
F
Variable Orifice Valve
Replies
10
Views
398
Fitz98
JohnnyG
Tricky A/C problem with Ford truck
Replies
6
Views
429
JohnnyG
A
how long for engine to cool down with hood open to change plugs?
2
Replies
25
Views
1K
Dave9
K20FA5
AC low side really high pressure?
Replies
3
Views
632
K20FA5
Back
Top