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Discussion Starter #1
Wassup to the Gang!!! I've been studying the A/C system for these cars for a while & cant get a break. So far I've changed everything listed fairly new or a year old.Using Auto Zone (San tech AC Compressor Kit LTW always comes with New Accumulator and PAG Oil) Condenser, AC/Lines, Blower Motor, Resistor, and Orifice Tube expect the Evaporator. About 2 Years I had watched someone charge & e vac the A/C system using the manifold and it was super cold then it slowly leaked as compressor would turn off and on. I then swapped out the compressor @ AZ thinking there was a problem. I know more now then I did then as well as parts, Now the issue is the compressor engages fine but tends to blow cold for a while before causing temp to rise close to the "H" Mark. Also makes it hot in car which will result into rolling down window, to let gauge keep from overheating. After a hour or so can continue with A/C into problem reoccurs. I've been using the refrigerant at Walmart for $4.88 a can I know we require 1.75 lbs of Freon 28 oz approximately 3 cans. Besides no changing the evap what seems to be the problem? I have all the tools needed to proper service A/C besides recovery tank. Harbor Freight A/C Gauge & a Vacuum Pump works fine.

https://www.autozone.com/cooling-heating-and-climate-control/a-c-compressor/santech-ac-kit-a-c-compressor/479589_576006_0
 

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What year car?


I've been using the refrigerant at Walmart
Is it 134 or 134a?


If all electric fans do they turn freely? They should spin after key off for a second or two. Safely hand turn them hot and cold. There should be no noise. They should turn freely.


Do both fans run?


If you have a mechanically powered fan does it make more noise when you overheat? Does it have a fan shroud?



Do you have the splash shields(front under car air dam, skirt) or is it missing.
 

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Discussion Starter #3 (Edited)
Would The Freon make a difference?

It's a 1994 Chevy Caprice 5.7L. I've been using this Super Tech Refrigerant R-134a. What's the difference between 134a & 134?


Both fans work have setup to run once keys are in Acc.


No splash shields that I see under car I am missing cover on passenger side by Charcoal canister. Where's the Air Dam?
 

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134a no problem.

Look for the skirt air dam or whatever you want to call it under the front bumper.
It will look sorta like the picture.It is made of three parts. In your environment you need all parts.


If it is missing it may cause the car to run hotter. Probably not your main problem.


I know little about the AC system but if your radiator and condenser do not get enough air flow you will have problems.
 

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Look for the skirt air dam or whatever you want to call it under the front bumper.
It will look sorta like the picture.It is made of three parts. In your environment you need all parts.


If it is missing it may cause the car to run hotter. Probably not your main problem.

I drove my 1994 9C1 Caprice every day for 17 years in Detroit's bumper to bumper traffic without the air dam ever being on there and it never overheated once so it is not really that big of a deal for it to be missing.


Mike--94MSP9C1
 

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With respect I would not compare Michigan with Arizona. Their lowest average temperature in January is higher that your highest. Their average high is over 85F for six months of the year, Michigan's average highest is 83F for a month.


Detroit

Month Low High
Jan 17.8°F 31.1°F
Feb 20.0°F 34.4°F
Mar 28.5°F 45.2°F
Apr 38.4°F 57.8°F
May 49.4°F 70.2°F
Jun 58.9°F 79.0°F
Jul 63.6°F 83.4°F
Aug 62.2°F 81.4°F
Sept 54.1°F 73.7°F
Oct 42.5°F 61.2°F
Nov 33.5°F 47.8°F
Dec 23.4°F 35.9°F







Tucson:
Month Low High
Jan 38.9°F 64.5°F
Feb 41.6°F 68.4°F
Mar 45.1°F 73.3°F
Apr 50.5°F 81.5°F
May 58.6°F 90.4°F
Jun 68.0°F 100.2°F
Jul 73.4°F 99.6°F
Aug 72.4°F 97.4°F
Sept 67.7°F 94.0°F
Oct 57.0°F 84.0°F
Nov 45.1°F 72.3°F
Dec 39.2°F 64.6°F
 

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Okay, I live in a similar environment, so I may be able to help.

To start:

1. Do you have access to a diagnostic dongle or some other device where you can actually monitor true temperatures the PCM see from the sending unit in the water pump?
*Granted the dash gauge sending unit in the RH cylinder head is good, and you certainly shouldn't see the gauge going to the "H" position, but being able to see actual PCM temperatures would verify whether you are ~actually~ running hot.
*If so, what is the temperature?

2. Do you have the flexible rubber pieces installed at the front of the condenser on each side?

3. What thermostat is installed; how old is it?

4. Where is the fluid level in the overflow tank? It should be level with the piece that runs from left to right at the fill opening.

5. Do both cooling fans engage when the A/C is engaged?

6. What are the high and low side A/C pressures at what ambient temperature and humidity percentage?

7. Has the PCM been reprogrammed to lower the temperatures at which the cooling fans turn ON/OFF?
 

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With respect I would not compare Michigan with Arizona. Their lowest average temperature in January is higher that your highest. Their average high is over 85F for six months of the year, Michigan's average highest is 83F for a month.


Detroit

Month Low High
Jan 17.8°F 31.1°F
Feb 20.0°F 34.4°F
Mar 28.5°F 45.2°F
Apr 38.4°F 57.8°F
May 49.4°F 70.2°F
Jun 58.9°F 79.0°F
Jul 63.6°F 83.4°F
Aug 62.2°F 81.4°F
Sept 54.1°F 73.7°F
Oct 42.5°F 61.2°F
Nov 33.5°F 47.8°F
Dec 23.4°F 35.9°F







Tucson:
Month Low High
Jan 38.9°F 64.5°F
Feb 41.6°F 68.4°F
Mar 45.1°F 73.3°F
Apr 50.5°F 81.5°F
May 58.6°F 90.4°F
Jun 68.0°F 100.2°F
Jul 73.4°F 99.6°F
Aug 72.4°F 97.4°F
Sept 67.7°F 94.0°F
Oct 57.0°F 84.0°F
Nov 45.1°F 72.3°F
Dec 39.2°F 64.6°F

And this statement is supposed to some how invalidate what I said? I think not! The point was you can drive without an air dam and not overheat!


And just to add clarity I drove my Caprice without the air dam from Detroit to Oklahoma and then drove to Las Vegas and went to a police car auction and purchased 22 Caprices and shipped them back east. I then drove on to Tucson Arizona to visit a friend and it was 118 degrees in Tucson and 123 degrees in Phoenix while I was there and my car did NOT overheat! But what do I know?


Mike--94MSP9C1
 

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5. Do both cooling fans engage when the A/C is engaged?
7. Has the PCM been reprogrammed to lower the temperatures at which the cooling fans turn ON/OFF?
juniorwatson


Both fans work have setup to run once keys are in Acc.
Dae1


I interpreted this to mean the fans run at all times the key is in run. All accessory power is active when the key is in RUN.



If it is missing it may cause the car to run hotter. Probably not your main problem.
Z09B4U

The point was you can drive without an air dam and not overheat!
Mike--94MSP9C1
 

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Mike--94MSP9C1 has pointed out to me that I was not clear enough when I said:


I know little about the AC system
POST#4



Again I am no expert.


It is a misconception that the "Great White North" is always cold. Today it will be 88F. It can get hotter.



My PERSONAL experience is that removing the air dam seemed to push the temperature gauge a little higher. I have had similar experiences with other vehicles.
 

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I interpreted this to mean the fans run at all times the key is in run. All accessory power is active when the key is in RUN.



Z09B4U

This could quite possibly be part of his issue. If the fans are running at speeds above 45mph they actually block more air then they allow in. Above 45mph the fans should not be running so the maximum amount of fresh air passes through the radiator.


Mike--94MSP9C1
 

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Here in ATL, I ran into the same issue as you when I reworked my AC with all new stuff.

Answer the questions in #7 and that'll get us going down the right path.
 

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Fans shouldn’t be on at all times, especially highway speeds. How are you determining that you have the proper amount of R134? 3 of those cans will result in a system that’s 1/2 lb overcharged. Was the system put into a vacuum before charging?


I agree on the air dams not making a difference. I took my broken ones off when I got the car 18 years ago. Lived in Phoenix for awhile, drove it on other occasions during summer months to Cali, Mexico, and the East coast. Never had an overheating issue. Currently been running my new system(compressor/condenser) for 2 summers in Chicago without issue as well. A few days this week it was 100 degrees with 80% humidity and sunny. Even in traffic, ac blows cold and car doesn’t overheat.
 

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Discussion Starter #16
Okay, I live in a similar environment, so I may be able to help.

To start:

1. Do you have access to a diagnostic dongle or some other device where you can actually monitor true temperatures the PCM see from the sending unit in the water pump?
*Granted the dash gauge sending unit in the RH cylinder head is good, and you certainly shouldn't see the gauge going to the "H" position, but being able to see actual PCM temperatures would verify whether you are ~actually~ running hot.
*If so, what is the temperature?


Answer to your first question I don't have a specific tool, but yesterday did come across this chart on shbox.com to help measure temp using multi meter. I haven't check the temperature on the two sensors yet. I know both sensors work fine usually reads close to L or as it doesn't work. Due to extreme heat here in Phx right now reads in the middle mostly out the day.

4th Gen LT1 F-body Tech Articles

"Use a Digital Volt Meter (DVM) set to ohms to measure resistance. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM. Most modern DVMs will do, but your old analog meter can damage the PCM. It is also a good idea to get a " reference" from the meter you are working with. With the DVM on the ohms scale, touch the two meter leads together and note the ohm reading. It may not always be perfectly zero, but may be within a tenth or two. Now when you take an ohm reading, you will know what the meter will show when there is really no resistance.
The sensor in the head has only one terminal. This sensor is for the temperature indicator on the dashboard. Place one test lead on the sensor terminal and the other on a known good ground. Compare the reading to the table. If your car is cold from sitting overnight, the reading should be close to ambient temperature.
The sensor in the water pump has two terminals. This sensor is for the temperature input to the PCM. Place a test lead on each of the sensor terminals to take the reading. (When reading resistance, it does not matter which lead goes to which terminal)
If the sensor seems to be ok, you may also need to test at the harness connector for proper lead conditions. Use your test meter set on the dc voltage scale to do this. You will need the key in the RUN position, but don't have to start the car."

ECT Temperature vs. Resistance Values

ºC ºF Ohms
100 212 177
90 194 241
80 176 332
70 158 467
60 140 667
50 122 973
45 113 1188
40 104 1459
35 95 1802
30 86 2238
25 77 2796
20 68 3520
15 59 4450
10 50 5670
5 41 7280
0 32 9420
-5 23 12300
-10 14 16180
-15 5 21450
-20 -4 28680
-30 -22 52700
-40 -40 100700







2. Do you have the flexible rubber pieces installed at the front of the condenser on each side?



Are those the little pieces at the both, to help support Condenser I should have not sure believe I'm missing the ones for radiator through.




3. What thermostat is installed; how old is it?


The One from Autozone believe its the Fail Safe one; Not that old about 6 months to almost a year ago.


4. Where is the fluid level in the overflow tank? It should be level with the piece that runs from left to right at the fill opening.


Its usually little over the Fill Line, I don't have coolant reservoir with any attachment just the 15 psi cap.



5. Do both cooling fans engage when the A/C is engaged?

Yes, I keep fans on at run due to its always hot in the summer these Caprice/Impala worst Nightmare tend to overheat so i try to avoid. I due agree about the fact it can tend to block the air due to fans & high speeds. Would a toggle switch work best? Ability to control the fans ON/Off



6. What are the high and low side A/C pressures at what ambient temperature and humidity percentage?



Cant remember was between 40-50 psi looking at the ambient chart, was about 100* that day. I need to find the problem before I just go head and re service the A/C System my self, its either the evaporator going bad or just cheap Freon I've never had problems like this before. Blows cool for roughly 5 to 10 mins or temp rises.



7. Has the PCM been reprogrammed to lower the temperatures at which the cooling fans turn ON/OFF?


No its a 1994 wouldn't think I need the PCM reprogrammed, I have both fans ran to a single Bosch relay I believe I have my own diagram; Isn't setup stock because I can run fans without the two relays under hood.
 

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Discussion Starter #17
Fans shouldn’t be on at all times, especially highway speeds. How are you determining that you have the proper amount of R134? 3 of those cans will result in a system that’s 1/2 lb overcharged. Was the system put into a vacuum before charging?


I agree on the air dams not making a difference. I took my broken ones off when I got the car 18 years ago. Lived in Phoenix for awhile, drove it on other occasions during summer months to Cali, Mexico, and the East coast. Never had an overheating issue. Currently been running my new system(compressor/condenser) for 2 summers in Chicago without issue as well. A few days this week it was 100 degrees with 80% humidity and sunny. Even in traffic, ac blows cold and car doesn’t overheat.
I Agree fans shouldn't be on at all times, would you suggest a toggle switch? I vacuum the system before charging each time have all the equipment handy. Last time which was about 2 months ago I don't think I even used the third can I wait till compressor remains on as well as the reading from the gauge to in sure system is charged. Two cans equal 24 OZ so .04 From the last can would be correct, using a scale. I read somewhere on the forum just charge to 40 lbs and should be fine anything over would overcharge suggesting temperature doesn't matter?
 

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The answer is that you have the fans rigged wrong. The question about the thermostat meant the temp rating of the thermostat not the brand. If you are smart, you will run a 160 degree thermostat with the PCM re-programmed for lower fan on and off temperatures. There are several threads here that indicate what the revised temperatures are. Stop screwing around with switches and program the PCM properly which should should have done when you acquired the car. A PCM performance tune would not hurt either and will extend the life of your transmission. Put the air dams back in place and disregard advice from people who say that they don't matter. What they mean is that they are too cheap or lazy to install them. They would not be there if GM engineers thought they were not needed. The suggestion about the radiator is a good one. Replacing it will make a world of difference to cooling. Just a stock replacement is sufficient and doesn't cost a fortune. The side tank is a pressurized reservoir not an "overflow tank" which is something entirely different. Read relevant threads on this forum and you will save yourself a lot of headaches. Get a Haynes Manual or a FSM if you intend to work on these cars. A lot of stuff that pertains to SBC's does not apply to LT-1's so it is good to educate yourself. Good luck.
 

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I still am not clear on when you overheat.
Under all conditions?
Stuck in slow traffic?
Urban 30MPH?
Highway speeds.


As has been said running the fans at higher speeds makes things worse. I tried it once since most of my drive was at 50MPH it added heat.


Put the air dams back in place and disregard advice from people who say that they don't matter. What they mean is that they are too cheap or lazy to install them. They would not be there if GM engineers thought they were not needed.
fbi9c1


On a side note, one item that gets overlooked is the center air-dam. If that booger is missing, or even bending back, it DOES run hotter at speeds above 40 or so, where the fans have little effectivene
ss.
jkilo Post#18
The Lazy Destroyer, fbi9c1 and Marky Dissod like this.


Oh, and nice catch regarding the air damns.
(Clear Image Automotive sold an upgrade central air damn which was even more effective than the OEM, but it is out of production; it was slightly canted forward to shove even more air thru the radiator.)
Marky Dissod Post#24

Air dams fixed it up. Before installing I checked and the temps rose even in OD at mild highway speeds, so towing had no bearing on the temps.
Temps are now solid as a rock at all driving conditions.
The Lazy Destroyer Post#28

The air dam is important for another reason, besides directing air into the radiator: It also stops the radiator from eating its own discharged hot air.
Viceroy Post#35

http://www.impalassforum.com/vBulletin/34-engine-problems-maintenance/1287529-overheating-towing.html

Done many experiments regarding this. Anything you do will make that opening even smaller. Anything extending down far enough to be effective will get tore-up. The most effective is a vertical dam similar to stock that creates a large low pressure area behind the radiator. I extended the stock depth with a strip of cloth impregnated rubber that's only a couple inches off the ground. Easily moved away by steep driveway aprons,speed bumps,etc,etc... Very effective at keeping coolant temps stable.
1slow96 Post#2


The air dam creates a significant low pressure area behind the radiator. This draws air up,and through that opening behind the bumper which has already created a low pressure area of it's own right there. Pretty ingenious,and resistant to rocks,debris,etc,etc...
1slow96 Post#10



Basically... the lt1 cools as a "bottom feeder" for the moving air. If u remove it... u will lose some cooling.
popo8 Post#12


http://www.impalassforum.com/vBulletin/3-exterior/1293818-front-air-dam-replacement.html

I guess your results may vary. Probably on the condition of your cooling system/radiator...
I've heard people take that piece off and have IMMEDIATE cooling issues around town. When they replaced the piece the cooling issues disappeared. It IS supposed to be an important part of the cooling system.
I've also heard of it having zero effect. I wonder if, as stated above, those people have 160 stats and programming to make it run cooler?
The point being...
Big Kahuna Post#11

From my experience, the airdam is most important when the car is NOT experiencing or generating a headwind; when the fans have to do the work themselves, the airdam helps them do their job more quickly.
Once moving along at highway speeds, the airdam is less necessary, even if it still helps the temps drop a bit faster.
Marky Dissod Post#12


http://www.impalassforum.com/vBulletin/9-misc/319337-plastic-strip-under-radiator-bolts-core-support-2.html



Thought some people might like a second opinion on the air dams so I looked at three threads then I got bored.
 
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