Testing the AC system

[boostedt28]

I am having this issue lately when running the AC during the heat of the day. The car seems to want to run hot (not overheating) at around 213°-216°. But when I turn the AC off, the temps come down to 196°-206° (which are normal for my car and route home). I noticed the car wouldn't idle up when the compressor kicked on and would stall out when coming to a stop. So I fixed the leak at the throttle body shaft and put in a NEW ISC motor. Now the car idles up and doesn't stall out coming to a stop, but it sounds like the car is really struggling at idle. I have searched and found mention that maybe the compressor is putting too much of a drain on the car, but there is no mention of testing it. So, can someone give me some advise on testing the draw the compressor is supposed to put on the car.

Car has a: 170° thermostat, front mount (no ducting), 12" puller with shroud, 10" pusher (wired to operate as stock fans would), manifold heat shield in place, blanket on turbine housing, downpipe/O2 housing wrapped, CAI

 

[Defiant]

Replace that thermostat with factory spec, to start. It's doing nothing to help cool the engine.

 

[PieEyedPiper]

Its also possible that using a fan setup, other than stock, might not be doing you any favors.

 

[boostedt28]

Replace that thermostat with factory spec, to start. It's doing nothing to help cool the engine.

Is it doing anything to hurt the engine? If the stock thermostat is 180° (fully open by 203°), what does it hurt to run the 170° during the humid Texas summer? I would like to see something on this, seriously.

Its also possible that using a fan setup, other than stock, might not be doing you any favors.

So are you saying the aftermarket fans are pulling that much load while the AC is on? I can turn the fans on full high without the AC and the car doesn't change rpm by more than 100rpm, going right back to where it was idling at after catching itself.

I'm not worried about the temperatures. Though they are a bit high, it has been a humid 100+ and I come home in stop and go traffic during the hottest part of the day. I am wondering how I test the load the AC compressor is putting on the car and what is supposed to be normal.
Defiant, if you could point me to some of your vast knowledge. I would love to read up on thermostats and pros and cons of cooler thermostats. Can never learn to much.

 

[turboglenn]

I had to go back to stock fans to be able to use my AC and not over heat. I tried several different slim lines, flex-alites, and Spal,, none of them worked... I re-routed the IC pipes to clear the stock fan, ran a 190* t-stat and she's been good to go. The heat index was 115 on Friday and i drove for over an hour with no issues using the AC

One thing to note, A cooler t-stat doens't always make the car run cooler.. Sometimes it will not stay closed long enough to let the water in the radiator get cooled by the air. This is a perpetuating cycle because the cooler t-stat will never get to close because the water wont' come down to a low enough temp since it's not spending much time in the radiator getting cooled. It will simply keep circulating and heating up until you've boiled over or are just running way too hot.

It's not that the fans are pulling too much load, it's that they aren't designed for your cars specific cooling system and therefor dont' pull as much air through as good as the stockers do. Go back to stock and you will have your AC back, i garauntee it (as long as there's no issues with your radiator leaking or anything )

 

[boostedt28]

Well with this turbo and manifold setup, the stock fans won't work with the aftermarket radiator. I tried to keep them, but short of notching the core support and pushing the radiator right against the condensor it won't happen.

You ran a 190° thermostat in a 2g turbo? Stock is 180°, so where did you find that higher temp thermostat? Makes sense about not letting it stay in the radiator long enough.

The AC blows ice cold, ALL the time. I will do some looking into the thermostat and fan solutions. But like I said, I'm not worried about the temps. I know there are things I need to do to bring them down. If you would see my setup, you would understand why everything is wrapped. Lesson learned about letting other do your piping on a mock up motor, and not the car itself. That's being fixed, slowly. Then maybe I can move the stock fans back onto the car.

My issue I want help with is underlined in my last post. How do I test the load the compressor puts on the car and what is normal? The car sounds like it is struggling during idle when the compressor kicks on. ISC cycles the rpms up, but the car just sounds off with the AC on. There are NO boost leaks either.

 

[Boosted98gsx]

I miss cold A/C. I just went and bought a new compressor / clutch pack / dryer to get mine working again, and installed an 11" pusher SPAL on my drivers side of the condensor (big turbo wastegate dump means no stock fans anymore). Hope I get my cold air back.

 

[Defiant]

Is it doing anything to hurt the engine? If the stock thermostat is 180° (fully open by 203°), what does it hurt to run the 170° during the humid Texas summer? I would like to see something on this, seriously.

The DSM engines run hot. Everything about them is calibrated to run hot. Over 200°. Run the stock thermostat. Seriously.

 

[boostedt28]

The DSM engines run hot. Everything about them is calibrated to run hot. Over 200°. Run the stock thermostat. Seriously.

I will swap a stock one in during the next oil change, but if the car runs between 196° and 206° I don't see that as being a problem. Everything cycles and acts like it's supposed to (except for the issue I'm trying to get answered). Will the stock thermostat allow the car to stop sounding like it is struggling with the AC on at idle, when the car is within the stock operating specs in the FACTORY shop manual for my year car?

My question is, how much load is the compressor supposed to pull when running and what is normal?

However, I'm guessing everyone is focused on the temperature my car runs at when that is not my issue.

 

[PieEyedPiper]

I will swap a stock one in during the next oil change, but if the car runs between 196° and 206° I don't see that as being a problem. Everything cycles and acts like it's supposed to (except for the issue I'm trying to get answered). Will the stock thermostat allow the car to stop sounding like it is struggling with the AC on at idle, when the car is within the stock operating specs in the FACTORY shop manual for my year car?

My question is, how much load is the compressor supposed to pull when running and what is normal?

However, I'm guessing everyone is focused on the temperature my car runs at when that is not my issue.

You say your A/C is hard on the car when operational. You have an old, tired, possibly near seizing A/C compressor. So do I.
No it is not normal. It's old.

The math should be pretty easy.

Let us know how much you pay for a new compressor.

 

[turboglenn]

Without dyno'ing the car with and without the AC running I doubt there's anyway to know "how much" the compressor is pulling from the motor, but it does take a decent amount. My car doesn't have en ECU with the feature to increase idle speed when the AC is on so i keep my idle at about 1k RPM...When the AC is on it will then idle at 800. But i feel a huge power loss with having the big turbo on my car since it doesn't want to spool until 3500 RPM or more. I have my AC set to turn off at 4500 RPM or 75% throttle and will stay off for 5 seconds after the conditions are right for it to operate again.. SO when i take off in first and feel that bog, i just slap the pedal to the floor for a second then the compressor kicks out and i can get the RPM's up enough to have power again.

You don't feel this so much on a stock car or V8 vehicles where torque in the low RPM's is abundant. But you sure feel it on an 8:1 1g motor with a big garrett on it.

As for the 190* t-stat = O'reilly's

 

[boostedt28]

You say your A/C is hard on the car when operational. You have an old, tired, possibly near seizing A/C compressor. So do I.
No it is not normal. It's old.

The math should be pretty easy.

Let us know how much you pay for a new compressor.

Won't cost anything because when it goes out, it comes out! I have another car to drive with a cold ac, and no mods!

Without dyno'ing the car with and without the AC running I doubt there's anyway to know "how much" the compressor is pulling from the motor, but it does take a decent amount. My car doesn't have en ECU with the feature to increase idle speed when the AC is on so i keep my idle at about 1k RPM...When the AC is on it will then idle at 800. But i feel a huge power loss with having the big turbo on my car since it doesn't want to spool until 3500 RPM or more. I have my AC set to turn off at 4500 RPM or 75% throttle and will stay off for 5 seconds after the conditions are right for it to operate again.. SO when i take off in first and feel that bog, i just slap the pedal to the floor for a second then the compressor kicks out and i can get the RPM's up enough to have power again.

You don't feel this so much on a stock car or V8 vehicles where torque in the low RPM's is abundant. But you sure feel it on an 8:1 1g motor with a big garrett on it.

As for the 190* t-stat = O'reilly's

After doing some more reading, I'm starting to lean towards the fact that it has a huge lazy turbo, over the top cams that create LOW vacuum, and already has the idle set to 1000 just to keep my teeth from chatter on each other type of "street" car. It blows cold, idles decent, and is atleast running so I'll just leave it as is. This is something that I just noticed while working on the idle, and thought I was ask about it.

I'm going to look into that thermostat and see if there are any differences in my temperature readings.

Thanks for the help.

 

[Galaxy]

I know this is old but for anyone with the same question about the draw the compressor has on the motor,remove the ac belt and restart the car,check the idle.