Micro-Tube Parallel Flow Condenser

[Dissent]

Here's some vent temp feedback after sitting at work all day with all 4x windows cracked about 3/4" and 105F ambient temp. I opened the driver's door and left it open for about 1 minute, open and shut the rear door to toss my backpack in, otherwise did not vent the truck as usual (roll down all windows and lift the hatch to let the heat escape). All the figures below are based on the lowest temp observed. The compressor cycling caused a deviation of 3-5F in all conditions.

I have a new 12" SPAL 12v fan on order to replace the 12" SPAL 24v one running now. It should be here by Saturday. I'll throw it on and do some more testing. I'd like to see the idle temps a bit lower for when I'm out wheeling. I'll also tie in the Trinary switch/automatic fan function this weekend and report back.

In all, I'm very happy with the results considering I am fairly new to full AC work and I suspect a shop may get it down a smidgen more but I'll take this over the 20F higher temps I've had all summer! I'm half tempted to take it to a pro shop and have them evac and charge to see what they get but I'm poor now.

• After 1 minute idling - 73F
• After 3 minutes idling - 61F
  
• 10 minutes of street driving (5 miles) - 52-57F
  
• 1st mile on the freeway @ 35 MPH - 52F
  
• 2nd mile on the freeway @ 35 MPH - 50F
  
• 3rd mile on the freeway @ 45 MPH - 47F
  
• 4th mile on the freeway @ 60 MPH - 45F
  
• 5th mile on the freeway @ 50 MPH - 44F
  
• 6th mile on the freeway @ 65 MPH - 45F
• 7th mile on the freeway @ 40 MPH - 45F
  
• 8th mile on the freeway @ 55 MPH - 44F
  
• 9th mile on the freeway @ 55 MPH - 44F
  
• 10th mile on the freeway @ 55 MPH - 44F (started to rain heavy)
• Sitting at traffic light - 47F (started to rain heavy)
• 1 mile neighborhood streets @ 20 MPH - 49F
  
• Driveway parked - 45F

 

[Dissent]

I was asked about the effect of blocking some of the radiator with the foam and I too was a little concerned about that but I pretty much always run 193F and now it's running 190F. Mind you, I've only had 24 hours to test it but I'll see. I could use 2x thicker foam along the top and smash it between the condenser and the radiator support rail. Not much I can do about the sides without bending some sheet metal. Time will tell.

 

[smritte]

This is kind of a dumb question but, have you checked the calibration on your thermometer? The easy way is a glass of water with ice. Ice melting will hold 32 degrees until its melted. I have to re-calibrate mine every now and then.
Also is the thermometer in the center vent when testing? Center is closest point to evap. High humidity makes AC work harder and you probably had a bit of heat to pull out of the dash.

Scott

 

[Dissent]

This is kind of a dumb question but, have you checked the calibration on your thermometer? The easy way is a glass of water with ice. Ice melting will hold 32 degrees until its melted. I have to re-calibrate mine every now and then.
Also is the thermometer in the center vent when testing? Center is closest point to evap. High humidity makes AC work harder and you probably had a bit of heat to pull out of the dash.

Scott

I haven't calibrated the thermometer. I do have 4x of the same and they all read alike. I cant calibrate it really of it's off. Just have to compensate. It was center vent. Lots of heat in the dash, some humidity

 

[Dissent]

I haven't calibrated the thermometer. I do have 4x of the same and they all read alike. I cant calibrate it really of it's off. Just have to compensate. It was center vent. Lots of heat in the dash, some humidity

I just tested my thermometer and it's off a full degree so my temps are even better!
I've edited the values on the original post to reflect this.

 

[ARB777]

Anyone here has their climate control unit go bad and replaced already? My other cruiser that I just redid the whole system last april decided to start blowing hot air out of nowhere. I wasnt overheating. Checked the heater valve and its good. Just wondering if its common for the climate control to fail after certain miles/years.

Trying to finish up the plumbing for the rear today. Hopefully I have something to report later.

 

[GeoRoss]

I haven't calibrated the thermometer. I do have 4x of the same and they all read alike. I cant calibrate it really of it's off. Just have to compensate. It was center vent. Lots of heat in the dash, some humidity

Look at your thermometer and see if it has a hex head on the underside. It should be a 10mm or so. Put a wrench on it and rotate the thermometer casing in the appropriate direction.

 

[Dissent]

Look at your thermometer and see if it has a hex head on the underside. It should be a 10mm or so. Put a wrench on it and rotate the thermometer casing in the appropriate direction.

It's a folding probe electronic model. No adjustments that I can find.

 

[Dissent]

@flintknapper The vent temps are pretty good, about 43 is the lowest I'm seeing on the freeway, it then cycles to about 47-48. Cycles take about 12 seconds. Standing in traffic is about 55-60. My high pressure is good, a bit low at 325, I was expecting 350. The low side peaked at 45, I was expecting 50-55 given the 105F ambient.
I looked over the FSM troubleshooting and noticed a section stating "Immediately after air conditioning is turned off, refrigerant in sight glass stays clear". The cause is Too Much Refrigerant. I'm at about 29-30oz which is spec but @Dindu Nuffin ended up with 23oz. When I tried 23oz my vent temps idling/1500RPM was about 70 and a full stream of bubbles in the sight glass.
I'm half tempted to evacuate it and try starting at 23oz and slowly work up again but it's working way better than before.
I'm still going to replace the SPAL fan with a proper 12v pusher this weekend which may help the idle temps drop below 55-60. 43 on the freeway is pretty nice but can/should it go lower? My newest car is 2004 so I don't have much to compare to but I want to be realistic.
Any advice you can offer?

 

[smritte]

Don't put alot into sight glass diagnostics. If I'm filling and I know there is no air (vacuumed first), I add until the bubbles are gone. Im going to be close to my fill point. If Im watching my temp at same time I'll be able to dial it in from there.
You cant compare @Dindu Nuffin fill amount. If you have a few ounce's of oil more or less that will effect your pressure. Oil takes up space. You will still be within a few ounces of his providing either of you is not real high or low on oil.

Scott

 

[Dissent]

Don't put alot into sight glass diagnostics. If I'm filling and I know there is no air (vacuumed first), I add until the bubbles are gone. Im going to be close to my fill point. If Im watching my temp at same time I'll be able to dial it in from there.
You cant compare @Dindu Nuffin fill amount. If you have a few ounce's of oil more or less that will effect your pressure. Oil takes up space. You will still be within a few ounces of his providing either of you is not real high or low on oil.

Scott

Gotcha. So should I not expect a flow of bubbles when I turn the engine off?

 

[flintknapper]

Don't put alot into sight glass diagnostics. If I'm filling and I know there is no air (vacuumed first), I add until the bubbles are gone. Im going to be close to my fill point. If Im watching my temp at same time I'll be able to dial it in from there.
You cant compare @Dindu Nuffin fill amount. If you have a few ounce's of oil more or less that will effect your pressure. Oil takes up space. You will still be within a few ounces of his providing either of you is not real high or low on oil.
Scott

^^^^^ Thank You. I've been telling that to folks for years. I realize it is outlined as a procedure in the FSM, BUT it is best utilized only if you are way out in BFE and have no gauges to check pressures. There are various reasons why you would (or would not) have bubbles in the sight glass. Ranging from having too little to too much refrigerant. At high ambient temps a certain amount of bubbles might be present (flash gas), this would be considered normal IF the system is still cooling. Old lubricating oil (especially if contaminated) will look like bubbles. There are just too many ways for this supposed diagnostic tool to trip people up if they are not intimately familiar with A/C systems.

 

[flintknapper]

Gotcha. So should I not expect a flow of bubbles when I turn the engine off?

Yes. When 'properly' filled (not to be confused with optimized). Once the system is shut down, the high and low side pressures will try to equalize as the refrigerant reaches its 'static pressure'.

So...basically you will see the refrigerant 'foam' at first then the sight glass will become clear.

 

[-Spike-]

Then I crammed 2x bags of this 2" insulation around the perimeter and between the condenser and radiator to force airflow through, rather than around, the condenser. Thanks @-Spike- for this tip.

It's been pointed out to me that a better solution would be to fashion some sheet metal blanks to block off the spaces instead of the foam to eliminate the chance of the foam coming loose and causing issues, such as partially blocking the radiator. So, you've been warned.

 

[flintknapper]

@flintknapper The vent temps are pretty good, about 43 is the lowest I'm seeing on the freeway, it then cycles to about 47-48. Cycles take about 12 seconds.

43° F vent temp @ 105° ambient is not 'pretty good' that is stellar. Think about it. That is a 60+ degree drop in temperature (ambient vs. vent). The fact that the system 'cycles' is proof that unit is working well (for those temps).

Standing in traffic is about 55-60. My high pressure is good, a bit low at 325, I was expecting 350. The low side peaked at 45, I was expecting 50-55 given the 105°F ambient.

Those look like good numbers to me. I would expect low side to be about 50-55 psi and high side about 330-335 psi depending on the relative humidity. IF your R/H was at or below 30% then we would shift those numbers down a bit.

I looked over the FSM troubleshooting and noticed a section stating "Immediately after air conditioning is turned off, refrigerant in sight glass stays clear". The cause is Too Much Refrigerant. I'm at about 29-30oz which is spec but @Dindu Nuffin ended up with 23oz. When I tried 23oz my vent temps idling/1500RPM was about 70 and a full stream of bubbles in the sight glass.

Next time you are in your FSM take a black magic marker and redact everything related to the sight-glass. IMO...it is a diagnostic tool of very limited value. IF you don't have a set of gauges and a way to measure vent temps...then yes, use it as a remedial way to determine an 'acceptable' refrigerant charge. But if you have gauges (you do) and a temp gauge (you do) use THEM. This is 2018....'We have the technology'

I'm half tempted to evacuate it and try starting at 23oz and slowly work up again but it's working way better than before.

NO...! Drive your vehicle for awhile under various conditions and take notes. Later on we can use your data to see if it is worth chasing down that last 1 or 2 degrees (or even possible).

I'm still going to replace the SPAL fan with a proper 12v pusher this weekend which may help the idle temps drop below 55-60.

Air flow is always a good thing.


I want to be realistic.
Any advice you can offer?

Yes, be 'realistic'.

^^^^^^^ Expand for replies

 

[Dissent]

It's been pointed out to me that a better solution would be to fashion some sheet metal blanks to block off the spaces instead of the foam to eliminate the chance of the foam coming loose and causing issues, such as partially blocking the radiator. So, you've been warned.

Now you tell me!!

 

[Dissent]

^^^^^^^ Expand for replies

As always, thank you so much for your (and other's) wisdom! I still have the haunting of the failed Dakota charge from last week that I'm second-guessing so I want to make sure I did this one right! I'll leave it alone, except for the fan. It does work much better. I'll try the Dakota from scratch tomorrow, still not sure how that one went sideways but now I have a scale to fill the prescribed 32oz for that system after a couple of hours on the pump. Thanks again!

 

[Dissent]

It's been pointed out to me that a better solution would be to fashion some sheet metal blanks to block off the spaces instead of the foam to eliminate the chance of the foam coming loose and causing issues, such as partially blocking the radiator. So, you've been warned.

I'll work on the sheet metal work when it cools off a bit. I also want to go back in and replace those clips that hold the wiring to the radiator support top rail. Interesting that I'm still about 3 degrees cooler with this setup. I'll keep monitoring it and plan on replacing that foam on the sides with sheet metal and move the top foam between the top rail and the condenser itself.

 

[flintknapper]

Delete: Not L/C related.

 

[Dissent]

Delete: Not L/C related