truck runs hot with A/C on - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jay55jay · 07-10-2011, 04:05 PM

Ok so i noticed that with the A/C on the truck runs about 210 with is off its around 185 or lower. The A/C starts off cold but as the temp goes up it gets warmer. I pulled over and the compressor was still running. I am not sure what this means. I did notice the compressor does not cycle it stays on constantly any thoughts thanks.

**Boog** · 07-10-2011, 06:13 PM

Does the fan clutch engage and run frequently?
210 running down the highway is above normal.
210 in town traffic is normal for this summer heat. Stop n go, long idle periods.
Do you trust your temp gauge to read reasonably corrrect?

jay55jay · 07-10-2011, 06:19 PM

210 is on local driving when I get going it cools off a bit.
The fan is On but it don't sound like it raises at all. The AC
Pump should cycle off on a hot day no? I was just investigating it
I noticed the recirculation door closes when recir is on. So would that
Cause the air to get warmer?
Posted via Mobile Device

**Boog** · 07-10-2011, 06:43 PM

So your engine temps don't sound far off normal for this time of year.
The a/c system is a cycling orifice tube design and it is supposed to cycle when the low pressure drops down low. Under normal conditions it might not cycle sitting there idling but hold the revs up for a few minutes and you should see the lowside pressure gauge dropping. They should cycle off around 15 to 20 psi and cycle on at around 40.
If the system is not cycling it can build excessive head pressure and not cool as well. The hotter that condensor gets in front of the radiator the hotter the radiator will be and harder to cool.
Turning on the recirculate you should notice the airflow sounds a lot stronger than on the fresh air setting. This is because it is drawing inside air. Air from the vents will be cooler than if drawing from the outside.
Sounds like you might need to have your a/c system evaluated.

jay55jay · 07-10-2011, 07:05 PM

So ur saying the temP is ok. I noticed what ur sayi g where it gets
Powerful with recirculator On. I noticed that the door that controls
Inside and outside air was opening and closing on it's on with
The recir button on? I have pod gauges and there both reading
The same temp around 210 at city driving.
Posted via Mobile Device

**Boog** · 07-10-2011, 08:25 PM

It's just a guess on my part but I bet you are experiencing hi 90* temps just like us right now. 100* here today. I have no idea how your traffic situation is. Your engine temp occasionally reaching 210 isn't alarming. Running steady at 210 and up is alarming. What condition is your cooling system in? What temp thermostat? Do you frequently have to add coolant? When idling does the engine fan blow hard, constantly?
By you stating the temp comes down once you get moving is good. It shows a lack of airflow through the radiator at low speed. Usually points toward the engine fan clutch. It should blow hard at low speed and freewheel at highway speeds. It is a thermostatic controlled clutch if it's still the original. They, like anything else, get weak with age.
I'm not telling you to go buy one to cure your problems. I'm just giving you some things to look at and check out.
That fresh/recirc door should not be opening and closing on it's own. Maybe a bad actuator. Do a forum search on those and you will find some good discussion on them.

jay55jay · 07-10-2011, 09:21 PM

Thanks for all your help i appreciate it. When the AC is off and i first start the truck the fan blows hard then it idles down to a free wheel motion. When the AC is on it kicks up. I never have to add colant not sure what temp thermostat is in the truck.The temp today climbed to about 210 then when i move or shut the AC off it goes back down. it never kept climbing i know that. I am guessing that that recir door might be the problem cause it must have closed on its on and the AC felt warmer. I have to research that. When the temp did climb i got out and opened the hood to check everything looked normal no leaks or bubbling sounds. The electric fan was on in front of the condenser..

**Boog** · 07-10-2011, 10:13 PM

So it has an auxilary fan in front of the condensor? Tells me it has had a heating issue since before you bought it, or did you add it?. Is the stock fan shroud in place and intact? When the engine is at full operating temp and idling the engine fan should be blowing strong constantly while the a/c is on.
If you have access to a compressor you could try blowing through the radiator fins from the engine side to remove any bugs or leaves that may be stuck in the fins or just use a garden hose with sprayer. Spray from the back side will force them back out the front. Do the same with the condensor if it looks like it needs it. Any thing to improve airflow.
By the way, what yr truck do you have?
You don't have one of those "custom" grille inserts with the small holes do you? Something else I don't like, it impeads airflow.

jay55jay · 07-10-2011, 10:51 PM

The fan is stock from gmc there is a sender on the drivers side head
That the wire looks brittle from the exhaust. Tonight I just got home stop and go. It stayed cool around 185 to 190. Recir door stayed open
After looking it was only going to about 200 earlier. The condenser looks dirty
I'm gonna try blowing it out tomm. Idk it performed perfect tonight
It was around 90 today. I think I hope it was cause of the blend door. Also
Infront of the condenser is a power steering cooler I think it's a 94 gmc C3500
Posted via Mobile Device

jay55jay · 07-10-2011, 10:52 PM

The shroud is all factory and the aux fan is to.
Posted via Mobile Device

jay55jay · 07-10-2011, 11:10 PM

I just took a closer look at the condenser
It looks like a dirty air filter bugs dust in-between the fins I have a air gun with a wand
I'm gonna try and clean it out. That wire I mentioned is not the fan sender.
It's the one on the passenger side that's the aux fan sender. I think it's a combo of the dirty condenser snd that recur door that closed on it's own.
Posted via Mobile Device

**Boog** · 07-10-2011, 11:31 PM

The temp sender in the driver's side head is for the temp gauge.
I wasn't aware the 1 tons came with an aux fan. Learned something new today. Big block?

jay55jay · 07-10-2011, 11:47 PM

Yes unfortunately 454 lol. It has every cooler imanginable.
I gotta search for that post on the recir door. The strange part is when I was trying to trouble shoot it today. When I turned off the A/C the door would shut that makes no sense to me.
Posted via Mobile Device

jay55jay · 07-11-2011, 05:34 PM

Ok im at a loss LOL. Last nite the AC worked perfect freezing cold. The temp stayed low around 165 id say. Today the AC was on and the temp climbed to about 210 and the Air got warmer. I sprayed the front of the truck down and the Air got as cold as a Meat Locker.. The temp also dropped back down. I am at a loss is this a cooling issue I am having. Fan maybe not pulling air in like it should any thoughts..?

07-10-2011, 04:05 PM	#1
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	truck runs hot with A/C on Ok so i noticed that with the A/C on the truck runs about 210 with is off its around 185 or lower. The A/C starts off cold but as the temp goes up it gets warmer. I pulled over and the compressor was still running. I am not sure what this means. I did notice the compressor does not cycle it stays on constantly any thoughts thanks.

07-10-2011, 06:13 PM	#2
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 14,116	Re: truck runs hot with A/C on Does the fan clutch engage and run frequently? 210 running down the highway is above normal. 210 in town traffic is normal for this summer heat. Stop n go, long idle periods. Do you trust your temp gauge to read reasonably corrrect? __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver 'primer is finer' Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

07-10-2011, 06:19 PM	#3
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on 210 is on local driving when I get going it cools off a bit. The fan is On but it don't sound like it raises at all. The AC Pump should cycle off on a hot day no? I was just investigating it I noticed the recirculation door closes when recir is on. So would that Cause the air to get warmer? Posted via Mobile Device

07-10-2011, 06:43 PM	#4
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 14,116	Re: truck runs hot with A/C on So your engine temps don't sound far off normal for this time of year. The a/c system is a cycling orifice tube design and it is supposed to cycle when the low pressure drops down low. Under normal conditions it might not cycle sitting there idling but hold the revs up for a few minutes and you should see the lowside pressure gauge dropping. They should cycle off around 15 to 20 psi and cycle on at around 40. If the system is not cycling it can build excessive head pressure and not cool as well. The hotter that condensor gets in front of the radiator the hotter the radiator will be and harder to cool. Turning on the recirculate you should notice the airflow sounds a lot stronger than on the fresh air setting. This is because it is drawing inside air. Air from the vents will be cooler than if drawing from the outside. Sounds like you might need to have your a/c system evaluated. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver 'primer is finer' Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

07-10-2011, 07:05 PM	#5
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on So ur saying the temP is ok. I noticed what ur sayi g where it gets Powerful with recirculator On. I noticed that the door that controls Inside and outside air was opening and closing on it's on with The recir button on? I have pod gauges and there both reading The same temp around 210 at city driving. Posted via Mobile Device

07-10-2011, 08:25 PM	#6
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 14,116	Re: truck runs hot with A/C on It's just a guess on my part but I bet you are experiencing hi 90* temps just like us right now. 100* here today. I have no idea how your traffic situation is. Your engine temp occasionally reaching 210 isn't alarming. Running steady at 210 and up is alarming. What condition is your cooling system in? What temp thermostat? Do you frequently have to add coolant? When idling does the engine fan blow hard, constantly? By you stating the temp comes down once you get moving is good. It shows a lack of airflow through the radiator at low speed. Usually points toward the engine fan clutch. It should blow hard at low speed and freewheel at highway speeds. It is a thermostatic controlled clutch if it's still the original. They, like anything else, get weak with age. I'm not telling you to go buy one to cure your problems. I'm just giving you some things to look at and check out. That fresh/recirc door should not be opening and closing on it's own. Maybe a bad actuator. Do a forum search on those and you will find some good discussion on them. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver 'primer is finer' Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

07-10-2011, 09:21 PM	#7
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on Thanks for all your help i appreciate it. When the AC is off and i first start the truck the fan blows hard then it idles down to a free wheel motion. When the AC is on it kicks up. I never have to add colant not sure what temp thermostat is in the truck.The temp today climbed to about 210 then when i move or shut the AC off it goes back down. it never kept climbing i know that. I am guessing that that recir door might be the problem cause it must have closed on its on and the AC felt warmer. I have to research that. When the temp did climb i got out and opened the hood to check everything looked normal no leaks or bubbling sounds. The electric fan was on in front of the condenser..

07-10-2011, 10:13 PM	#8
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 14,116	Re: truck runs hot with A/C on So it has an auxilary fan in front of the condensor? Tells me it has had a heating issue since before you bought it, or did you add it?. Is the stock fan shroud in place and intact? When the engine is at full operating temp and idling the engine fan should be blowing strong constantly while the a/c is on. If you have access to a compressor you could try blowing through the radiator fins from the engine side to remove any bugs or leaves that may be stuck in the fins or just use a garden hose with sprayer. Spray from the back side will force them back out the front. Do the same with the condensor if it looks like it needs it. Any thing to improve airflow. By the way, what yr truck do you have? You don't have one of those "custom" grille inserts with the small holes do you? Something else I don't like, it impeads airflow. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver 'primer is finer' Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

07-10-2011, 10:51 PM	#9
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on The fan is stock from gmc there is a sender on the drivers side head That the wire looks brittle from the exhaust. Tonight I just got home stop and go. It stayed cool around 185 to 190. Recir door stayed open After looking it was only going to about 200 earlier. The condenser looks dirty I'm gonna try blowing it out tomm. Idk it performed perfect tonight It was around 90 today. I think I hope it was cause of the blend door. Also Infront of the condenser is a power steering cooler I think it's a 94 gmc C3500 Posted via Mobile Device

07-10-2011, 10:52 PM	#10
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on The shroud is all factory and the aux fan is to. Posted via Mobile Device

07-10-2011, 11:10 PM	#11
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on I just took a closer look at the condenser It looks like a dirty air filter bugs dust in-between the fins I have a air gun with a wand I'm gonna try and clean it out. That wire I mentioned is not the fan sender. It's the one on the passenger side that's the aux fan sender. I think it's a combo of the dirty condenser snd that recur door that closed on it's own. Posted via Mobile Device

07-10-2011, 11:31 PM	#12
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 14,116	Re: truck runs hot with A/C on The temp sender in the driver's side head is for the temp gauge. I wasn't aware the 1 tons came with an aux fan. Learned something new today. Big block? __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver 'primer is finer' Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

07-10-2011, 11:47 PM	#13
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on Yes unfortunately 454 lol. It has every cooler imanginable. I gotta search for that post on the recir door. The strange part is when I was trying to trouble shoot it today. When I turned off the A/C the door would shut that makes no sense to me. Posted via Mobile Device

07-11-2011, 05:34 PM	#14
jay55jay Registered User Join Date: Mar 2010 Location: bayville,nj Posts: 165	Re: truck runs hot with A/C on Ok im at a loss LOL. Last nite the AC worked perfect freezing cold. The temp stayed low around 165 id say. Today the AC was on and the temp climbed to about 210 and the Air got warmer. I sprayed the front of the truck down and the Air got as cold as a Meat Locker.. The temp also dropped back down. I am at a loss is this a cooling issue I am having. Fan maybe not pulling air in like it should any thoughts..?



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