Wondering why, when stopped, the coolant temp climbs and the air vents blow warm. Car moves, temp lowers, and vents are cold again.
What does one have to do with the other?
What does one have to do with the other?
Coolant temp influence on AC output
- Thread starter mjoekingz28
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The electric cooling fans for the condenser/radiator are not coming on at low speed.
Lower airflow over the condenser coupled with a lower compressor RPM lowers the capacity of the A/C. So your evaporation temperature will rise and as a consequence discharge temps will be warmer.
Condenser will dump more heat into the radiator as it pre-heats the outside air, so in theory if your cooling system is marginal you'll see elevated coolant temperatures.
If it's more than a bit of a gnats cock of difference then you should probably have stuff looked at. A couple of degrees here or there is nothing to be concerned about. On 42C+ days here (107F) I've been known to sit at lights with the engine at about 1500RPM to keep the A/C cooler, but my car is 26 years old and the A/C was marginal from the factory.
Condenser will dump more heat into the radiator as it pre-heats the outside air, so in theory if your cooling system is marginal you'll see elevated coolant temperatures.
If it's more than a bit of a gnats cock of difference then you should probably have stuff looked at. A couple of degrees here or there is nothing to be concerned about. On 42C+ days here (107F) I've been known to sit at lights with the engine at about 1500RPM to keep the A/C cooler, but my car is 26 years old and the A/C was marginal from the factory.
I've had a number of cars that didn't cool as well in traffic, but I have not had any properly functioning cars coolant temp rise significantly at idle w/ a/c on. Usually having the A/C on also turns on the radiator fans.
I have had car that with the A/C off, the coolant temps would rise to ~225F before the fans came on and pulled the temp back down.
I have had car that with the A/C off, the coolant temps would rise to ~225F before the fans came on and pulled the temp back down.
You have 1772 post here on BITOG and you do not understand how heat is removed from the air conditioners condenser and the engines radiator.
One does not have anything to do with the other, though if the engines cooling system is not good the heat from the AC condenser warms the air before it goes through the engines radiator, and could cause the engine to run a couple of degree hotter.
Both are affected by the amount of air moving through them, and when the vehicle is moving there is more air moving through them, compared to when the vehicle is stopped and the only air that is moving through them is air pulled through them by the vehicles fan.
When stopped the coolant temperature climbs because there is less air moving through the radiator (the black thing that transfers heat from the engine coolant to air). When the vehicle is moving air hits the front of the vehicle and causes more air to pass through the radiator.
When stopped the air conditioner blows warmer air because because there is less air moving through the condenser (the air conditioners silver colored radiator looking thing in front of the engines radiator). When the vehicle is moving air hits the front of the vehicle and causes more air to pass through the air conditioners condenser. When more air moves through the condenser it can dump more heat into that air, and the gas refrigerant entering the condenser can change to a liquid easier, and the liquid refrigerant leaving the condenser is cooler. When the cooler refrigerant changes from liquid to gas inside of the evaporator it produces a colder temperature and the evaporator removes more heat from the air passing through it, making the air blowing into the passenger compartment colder.
Also when the engines RPM's are higher than idle the water pump and AC compressor are both turning at higher RPM's compared to being at an idle.
One does not have anything to do with the other, though if the engines cooling system is not good the heat from the AC condenser warms the air before it goes through the engines radiator, and could cause the engine to run a couple of degree hotter.
Both are affected by the amount of air moving through them, and when the vehicle is moving there is more air moving through them, compared to when the vehicle is stopped and the only air that is moving through them is air pulled through them by the vehicles fan.
When stopped the coolant temperature climbs because there is less air moving through the radiator (the black thing that transfers heat from the engine coolant to air). When the vehicle is moving air hits the front of the vehicle and causes more air to pass through the radiator.
When stopped the air conditioner blows warmer air because because there is less air moving through the condenser (the air conditioners silver colored radiator looking thing in front of the engines radiator). When the vehicle is moving air hits the front of the vehicle and causes more air to pass through the air conditioners condenser. When more air moves through the condenser it can dump more heat into that air, and the gas refrigerant entering the condenser can change to a liquid easier, and the liquid refrigerant leaving the condenser is cooler. When the cooler refrigerant changes from liquid to gas inside of the evaporator it produces a colder temperature and the evaporator removes more heat from the air passing through it, making the air blowing into the passenger compartment colder.
Also when the engines RPM's are higher than idle the water pump and AC compressor are both turning at higher RPM's compared to being at an idle.
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Sounds like you're low on refrigerant. Or your fan isn't working.
Nick1994
$100 site donor 2024
Make sure the electric fans are working.
Start checking cooling fan operation under a bunch of conditions (viscous clutch or electric)
I had a similar yet different problem lately on my Villager's single electric fan
Cooling fan only had two modes
-Off
-Light dimming full blast
So, idling hot in park with the air on would result in no constant fan operation, then 5 seconds of full blast, at nauseum...
Nothing FAAAAAAAAANNNNNNN
Nothing FAAAAAAAAANNNNNNN
Nothing FAAAAAAAAANNNNNNN
Oddly, low speed stop and go A/C performance was still good (all hail the FS10/FX15), but it was made even better by replacing the blown 20A low speed cooling fan fusible link, restoring proper cooling fan and A/C system function.
TL
R
Start checking the basics
Vehicle info and preliminary observations would help in making a shotgun diagnosis
I had a similar yet different problem lately on my Villager's single electric fan
Cooling fan only had two modes
-Off
-Light dimming full blast
So, idling hot in park with the air on would result in no constant fan operation, then 5 seconds of full blast, at nauseum...
Nothing FAAAAAAAAANNNNNNN
Nothing FAAAAAAAAANNNNNNN
Nothing FAAAAAAAAANNNNNNN
Oddly, low speed stop and go A/C performance was still good (all hail the FS10/FX15), but it was made even better by replacing the blown 20A low speed cooling fan fusible link, restoring proper cooling fan and A/C system function.
TL
R Start checking the basics
Vehicle info and preliminary observations would help in making a shotgun diagnosis
JHZR2
Staff member
This isn't very hard. The condenser is forward of the radiator. So any heat released from the AC condenser doesn't necessarily go into the doll ant, but it reduces the ability of the radiator to dissipate heat because the radiator works on the basis of a delta in temperature (water temp minus air temperature flowing through).
Phenomena #1 - difference in temperature between the first (hot) fluid, and the second (cold) one.
The other side of the equation is that a fan on the nose of the car can move a lot of air, but certainly not the amount that is ramming into the front of the car when it is moving. Stick your head out the window at 65 mph and see what I mean.
Phenomena #2 - mass flow going through the heat exchanger, more flow can take more heat for a given delta (see #1).
Phenomena #1 - difference in temperature between the first (hot) fluid, and the second (cold) one.
The other side of the equation is that a fan on the nose of the car can move a lot of air, but certainly not the amount that is ramming into the front of the car when it is moving. Stick your head out the window at 65 mph and see what I mean.
Phenomena #2 - mass flow going through the heat exchanger, more flow can take more heat for a given delta (see #1).
You have a engine cooling system problem. The higher temperature is causing the AC pressure switch to disengage the AC compressor to save your engine from overheating
Here in hot-n-sticky South Florida, my 2011, Ford F150 3.5L Ecoboost has awful air conditioning when stopped, such as when first starting up. In fact, it never gets really cool until I've driven for a while.
As you would expect, it's performance is not great in a typical Miami traffic jam.
Once going though, cooling is excellent. Charge level is perfect, and revving the engine up does nothing to help. I think it's simply a matter of airflow over the condenser.
As you would expect, it's performance is not great in a typical Miami traffic jam.
Once going though, cooling is excellent. Charge level is perfect, and revving the engine up does nothing to help. I think it's simply a matter of airflow over the condenser.
Originally Posted By: Cujet
Here in hot-n-sticky South Florida, my 2011, Ford F150 3.5L Ecoboost has awful air conditioning when stopped, such as when first starting up. In fact, it never gets really cool until I've driven for a while.
As you would expect, it's performance is not great in a typical Miami traffic jam.
Once going though, cooling is excellent. Charge level is perfect, and revving the engine up does nothing to help. I think it's simply a matter of airflow over the condenser.
air flow is the key.no air= no cooling.I have not ran across any of your truck yet.too new.
Here in hot-n-sticky South Florida, my 2011, Ford F150 3.5L Ecoboost has awful air conditioning when stopped, such as when first starting up. In fact, it never gets really cool until I've driven for a while.
As you would expect, it's performance is not great in a typical Miami traffic jam.
Once going though, cooling is excellent. Charge level is perfect, and revving the engine up does nothing to help. I think it's simply a matter of airflow over the condenser.
air flow is the key.no air= no cooling.I have not ran across any of your truck yet.too new.
Originally Posted By: Cujet
Here in hot-n-sticky South Florida, my 2011, Ford F150 3.5L Ecoboost has awful air conditioning when stopped, such as when first starting up. In fact, it never gets really cool until I've driven for a while.
As you would expect, it's performance is not great in a typical Miami traffic jam.
Once going though, cooling is excellent. Charge level is perfect, and revving the engine up does nothing to help. I think it's simply a matter of airflow over the condenser.
Mechanical or electrical fan? I bet i either case it just isn't turning, as the engine temp hasn't risen enough to do so.
Here in hot-n-sticky South Florida, my 2011, Ford F150 3.5L Ecoboost has awful air conditioning when stopped, such as when first starting up. In fact, it never gets really cool until I've driven for a while.
As you would expect, it's performance is not great in a typical Miami traffic jam.
Once going though, cooling is excellent. Charge level is perfect, and revving the engine up does nothing to help. I think it's simply a matter of airflow over the condenser.
Mechanical or electrical fan? I bet i either case it just isn't turning, as the engine temp hasn't risen enough to do so.
Originally Posted By: mjoekingz28
Wondering why, when stopped, the coolant temp climbs and the air vents blow warm. Car moves, temp lowers, and vents are cold again.
What does one have to do with the other?
Based on your user name, I suppose we can presume you have some sort of Z-28, but even in that arena, there have been a wide variety of configurations (including both electric and mechanical cooling fans). Year/make/model of vehicle will go a long way here...
Wondering why, when stopped, the coolant temp climbs and the air vents blow warm. Car moves, temp lowers, and vents are cold again.
What does one have to do with the other?
Based on your user name, I suppose we can presume you have some sort of Z-28, but even in that arena, there have been a wide variety of configurations (including both electric and mechanical cooling fans). Year/make/model of vehicle will go a long way here...
If it's electric, the condenser/radiator fan(s) will activate anytime A/C is on, so in theory A/C should be as good idling as moving(that's case for both my Grand Marquis)... A feature I believe added to newer vehicles(within last 6-8 years)the BCM will shut fan off if vehicle is at highway speed when getting plenty of air flow, as it can monitor ambient & engine temp, A/C pressures etc...
On the other hand, engine driven clutch/thermostatic fans are notorious for loosing their efficiency, especially at low speeds... That will cause loss in in A/C efficiency, and engine temp to rise... Surprisingly the one on my almost 20 year old beater F-150 still works fine, no noticeable increase in A/C temp idling... Engine temp will increase maybe a needle's with on gauge but most did same when new...
On the other hand, engine driven clutch/thermostatic fans are notorious for loosing their efficiency, especially at low speeds... That will cause loss in in A/C efficiency, and engine temp to rise... Surprisingly the one on my almost 20 year old beater F-150 still works fine, no noticeable increase in A/C temp idling... Engine temp will increase maybe a needle's with on gauge but most did same when new...
Originally Posted By: supton
Mechanical or electrical fan? I bet i either case it just isn't turning, as the engine temp hasn't risen enough to do so.
The Ecoboost has an electric fan. It runs anytime the AC is on, which is about all the time around here.
It does a great job of keeping the engine cool. It does not do a great job of pulling enough air through the condenser.
My 2009 F150 5.4L V8 has a huge, high blade pitch, mechanical fan with electric clutch. It's a cool setup and very effective. At idle, with AC on, the clutch engages and there is a roar of air under the hood and the AC is ice cold at idle or in traffic jams.
Same basic truck, very different methods of moving air through the radiator and condenser.
Mechanical or electrical fan? I bet i either case it just isn't turning, as the engine temp hasn't risen enough to do so.
The Ecoboost has an electric fan. It runs anytime the AC is on, which is about all the time around here.
It does a great job of keeping the engine cool. It does not do a great job of pulling enough air through the condenser.
My 2009 F150 5.4L V8 has a huge, high blade pitch, mechanical fan with electric clutch. It's a cool setup and very effective. At idle, with AC on, the clutch engages and there is a roar of air under the hood and the AC is ice cold at idle or in traffic jams.
Same basic truck, very different methods of moving air through the radiator and condenser.
Originally Posted By: TFB1
If it's electric, the condenser/radiator fan(s) will activate anytime A/C is on, so in theory A/C should be as good idling as moving(that's case for both my Grand Marquis)...
The variable still at play is actual A/C compressor output. One moving at 600 RPM engine speed won't pump as much refrigerant as one moving at 2,000 RPM engine speed. This will, naturally, vary with vehicle, compressor design, etc.
For example, I can't tell a difference in vent temperature in our Acura regarding idling or moving. But I can tell a difference in our CR-V -- it does feel a touch warmer slowing to a stop (when the engine is already at idle) and sitting at a traffic signal. Just a few seconds after I move off the light, and the engine speed rises, the vent temperature becomes slightly cooler again.
If it's electric, the condenser/radiator fan(s) will activate anytime A/C is on, so in theory A/C should be as good idling as moving(that's case for both my Grand Marquis)...
The variable still at play is actual A/C compressor output. One moving at 600 RPM engine speed won't pump as much refrigerant as one moving at 2,000 RPM engine speed. This will, naturally, vary with vehicle, compressor design, etc.
For example, I can't tell a difference in vent temperature in our Acura regarding idling or moving. But I can tell a difference in our CR-V -- it does feel a touch warmer slowing to a stop (when the engine is already at idle) and sitting at a traffic signal. Just a few seconds after I move off the light, and the engine speed rises, the vent temperature becomes slightly cooler again.
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