A/C vent temp too warm - pics inside (1 Viewer)

[alia176]

Guys,

I would like some feedback from the guys on this forum who are well versed on our A/C system. Couple of weeks ago, I was noticing that the vent temps from the '97 80 was a little more than 50° using a cheap mechanical analog gauge. Vehicle just came home from a long, hot run so everything was steaming hot in the engine bay.

The ambient temp (in front of the condenser) was 93°

The manifold pressure gauge was showing this

I thought that the low pressure side was showing too high of a number, around 105psi.

So, I let out some R134a and then got the following:

I was sitting in the driveway, so this is not a real world experiment. However, since then, my vent temps did decrease another five degrees to approx 45°. Reminder, this gauge is not super accurate but I'm really after the delta temp vs the actual temps.

Am I on the right track? Should I do anything else for a more efficient system?

Things done:
- evap removed from vehicle and totally cleaned out.
- expansion valve new
- evac and held vac at -30 Hg
- recharged with clean R134a out of 12oz cans from NAPA
- aux cooler in front of condenser that turns on/off with the Trinary press switch, right next to the drier.
- new drier
- blue fan clutch 10,000 CST

Thanks for any insights.

 

[Michael Hanson]

Hi, Original dryer? MIke

 

[Black Op]

My vent temps (as I was told) are 60* thats some cold A/C

 

[alia176]

My vent temps (as I was told) are 60* thats some cold A/C

for all I know, my vent temps are the same as yours. Don't pay a whole lot of attention to the $5 gauge!

 

[gtfour43]

I haven't checked the temp in my LC but in all other cars the ac would blow at least 42f.

60f would not cool the interior at all in this heat.

 

[Michael Hanson]

As your outside load went up( temp and hot engine) your inside temp rose.Im not sure what your asking? The cruiser is idling right? Im missing something here. MIke

 

[Bob_Garrett]

Have you checked to see if the heater control valve is fully closed? That made about a 5deg difference in my outlet temps.

Using the same type of gauge, I'm seeing about 42deg in normal driving. Haven't tested it recently at idle, but with 100+ deg ambient temps, I would expect the outlet temps to be higher.

 

[e9999]

were these pressure measurements taken with the engine going and the compressor running with engine at 1500? Knowing you you did. With recirc, high fan etc, 90F in etc you'd want 21-36 psi on the low side and 194-223 on the high (edit: just looked up numbers in FSM). So 30 and 225 looks good.

Any bubbles in the line?

50F is not bad at the vents with high temp outside but of course depends on the inside temp and the fan speed you chose. High fan speed = higher temp normally. Higher temp in gives higher temp out. 45 even better.

Altogether if I'm in the 40s or even 50 I would not be concerned. Looks like you're good. Why are you concerned?

 

[Michael Hanson]

Agreed. MIke

 

[jlg32281]

Wow, I could only dream of vent temps like that. I'm gearing up to tear into my system because my vent temps are right around 80* when it's 100* outside, worthless. I don't want to hi-jack, but do you have a threat to work you did to yours?

 

[e9999]

Wow, I could only dream of vent temps like that. I'm gearing up to tear into my system because my vent temps are right around 80* when it's 100* outside, worthless. I don't want to hi-jack, but do you have a threat to work you did to yours?

that is indeed a bit high. Start with checking if you have enough refrigerant. Might be as simple as adding some if you have a slow leak. Check for bubbles first if you don't have gauges.

 

[Black Op]

Quote:
Originally Posted by Black Op
My vent temps (as I was told) are 60* thats some cold A/C
for all I know, my vent temps are the same as yours. Don't pay a whole lot of attention to the $5 gauge!

Posted by gtfour43
I haven't checked the temp in my LC but in all other cars the ac would blow at least 42f. 60f would not cool the interior at all in this heat.



Today it is in the low to mid 90's with a lot of humididdy. A/C cools the TLC very nice. Maybe I was giving false info????

 

[Trollhole]

Wonder what the difference is in an R-12 system vs 134a? My R-12 system in my 93 puts out a steady 32 degrees on high recirculate when it's easily in the high 90's. On a low speed it will easily go below 32 degrees.

With outside air on high it will get around 40 and on low in the mid 30's.

It can flat out freeze you out of the car while moving.

It takes the interior about 5 min to get cool after baking in the sun.


So how well do the 134 systems perform?

 

[alia176]

As your outside load went up( temp and hot engine) your inside temp rose.Im not sure what your asking? The cruiser is idling right? Im missing something here. MIke

Maybe I don't know what I'm asking either! I'm asking the question to the folks who are in the A/C business and know if these pressures and temp correlation look close to factory.

Have you checked to see if the heater control valve is fully closed? That made about a 5deg difference in my outlet temps.

Using the same type of gauge, I'm seeing about 42deg in normal driving. Haven't tested it recently at idle, but with 100+ deg ambient temps, I would expect the outlet temps to be higher.

That is a good point about the heater valve and yes, mine is setup properly so no hot water is entering the system.

were these pressure measurements taken with the engine going and the compressor running with engine at 1500? Knowing you you did. With recirc, high fan etc, 90F in etc you'd want 21-36 psi on the low side and 194-223 on the high (edit: just looked up numbers in FSM). So 30 and 225 looks good.

Any bubbles in the line?

50F is not bad at the vents with high temp outside but of course depends on the inside temp and the fan speed you chose. High fan speed = higher temp normally. Higher temp in gives higher temp out. 45 even better.

Altogether if I'm in the 40s or even 50 I would not be concerned. Looks like you're good. Why are you concerned?

Good question. I don't think I had the engine revved to 1500 but everything else you mention, I did.

As you stated, my pressures (after leaking some r134a out on purpose), look good. I'm not sure if I'm really concerned but was curious if other folks are seeing lower vent temps in their 80. But, w/o seeing all the proper temps and pressures, it's hard to determine what the vent temps should be. Most people don't typically know/care what temps the condenser is seeing or what pressure is the system operating in.

I don't want to hi-jack, but do you have a threat to work you did to yours?

No problem on the hi-jack. You're in luck, I did a writeup on how I took this vehicle's A/C system completely apart. Here's the link: https://forum.ih8mud.com/80-series-...-cooling-unit-evaporator-expansion-valve.html

 

[LandCruiserPhil]

I have always seen AC performance rated with exchange difference. As the supply temp of air drops so should the output. If you are drawing your supply air from the outside (verses inside) I do see the output temps dropping any with run time. With that said what is your supply temp verses your output?

 

[1972FJ55]

Alia,

Your pressures are right in the normal range. For comparison, on my '97, the center vent temp is 40 degrees on med-low blower. Outside ambient is 93 degrees, humidity is 37, which is high for AZ, but we have storms blowing in. There can be slight variations between like vehicles even from the factory. You could try playing with the charge amount and see if that helps. You could also try measuring the inlet and outlet temps of the condenser. You should see between 30-50 degree difference in temps. If you're not seeing that kind of number, look to the fan clutch or making sure air can't flow around the condenser. Mine had a big gap on the top between the condenser and the core support that I sealed off with square weatherstripping. Also check to see if you have a bunch of fins folded over on the condenser, blocking airflow thru it.

 

[jlg32281]

that is indeed a bit high. Start with checking if you have enough refrigerant. Might be as simple as adding some if you have a slow leak. Check for bubbles first if you don't have gauges.

I am already planning on pulling the evap. and cleaning it. I will also be replacing the expansion valve and drier. Hopefully that will do it.

Wonder what the difference is in an R-12 system vs 134a? My R-12 system in my 93 puts out a steady 32 degrees on high recirculate when it's easily in the high 90's. On a low speed it will easily go below 32 degrees.

With outside air on high it will get around 40 and on low in the mid 30's.

It can flat out freeze you out of the car while moving.

It takes the interior about 5 min to get cool after baking in the sun.


So how well do the 134 systems perform?

My dad used to do residential AC work and he swears that R-12 is a far superior coolant. Is it possible to revert the R-134 system back to R-12?

 

[Tapage]

we have average of 80% humidity down here .. and 90°F - 96°F day temp .. leaving my car outside under sun and seen 140°F when I jump in .. it's really hard to get it under 60°F at ac vents ( same cheap gauge ).

If it's raining it will easily lower 50°F and cycle the compressor ..

Conclusion your temps depends so much if your car was under sun or running long time .. air flow in your condensor, humidty on your area and windo tint ..

 

[hzavarce]

Alia176, I did the same thing you did (thanks for the write up, it was great aid !).I was surprised at the amount of junk I had on my evap, and I was expecting to get better tempsI had a bit of improvement but not much. I have been doing a lot of temp readings and mine are very similar to yours.I have been taking readings on other vehicles too, and under the same conditions I see temperatures go below 45F.With the 100F days I want those 45 F !!! The only thing weird on mine is that the high pressure reading were higher than the expected range. I played with the charge and could not get it to change. Not sure if that has an adverse effect on the vent temp, or what might be causing that

 

[Tools R Us]

Agree, pressures look good.

Freon expands with temp increase, 134a more than R12, so pressure will always rise with temp increase. The A/C system pumps heat from inside and dumps it outside. One of the keys to an efficient system, is the ability to dump the heat so it doesn't over pressurize the system. More heat dumped = more efficient system. The two most effective strategies are: #1; Changing to a bigger condenser, not that practical on the '80. #2; Increase airflow over the condenser, this is best, first plan.

Next is to define "airflow". Coolers like the condenser work by transferring heat, over time as the Freon travels through the cooler tube. X number of degrees of heat transfer per foot of travel through the tube.

Electric pushers can help, sometimes, depending on setup, pusher size, main fan power, etc. With a stressed system, I have seen them slightly reduce vent temp or not make a difference or slightly increase it. The reason gets back to how the condenser works. Say the main fan moves 2000cfm, so with the shroud, that airflow is spread over the entire cooler. Say a 10"/1000cfm pusher fan is used, now it is aggressively pushing air through a small part of the cooler. Due to the effective airflow restriction reduction the main fan will move slightly more, but still most of the airflow comes through the small spot where the pusher fan is and the rest of the surface area of the cooler getting less, possibly even less than stock. So will have reduced heat transfer over much of the cooler area.

Think of this way, standing, sweating in the sun, press an ice cube on your arm, it does a great job of cooling the surface, vessels, in the local area, but you still feel hot? Now stand in front of a full body fan, it feels cooler, even though the temp difference is smaller, because heat transfer is more efficient over the larger area. The cooler works somewhat the same, airflow improvements over the whole surface area are much more efficient than spot improvements.

This leads to the most efficient, first choice improvement, the main fan, by improving the clutch. By far the most critical clutch function is at idle heat soak, just about any fan will work at cruise. Here, at idle heat soak, it isn't uncommon to see 160-200F fan output temps. In my observation, this is where the earlier clutches excel, they have more aggressive high temp valve profiles so are more powerful at higher temps. For good A/C performance a powerful main fan, that is optimized as much as possible for low speed/high temp performance is the best setup.