ac making engine run hotter
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Cross-Country
Joined: Sep 2007
Posts: 91
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ac making engine run hotter
when I run the AC at lower speeds, the engine run hotter: on the temperature indicator, where it says "normal" the needle stays around the "m". with the AC running, it will go all the way over to hot.
Do I need a better fan (stock) ? or is this something I just have to deal with. The engine is a 460 that was just rebuilt ( with RV cam)
Thanks
Do I need a better fan (stock) ? or is this something I just have to deal with. The engine is a 460 that was just rebuilt ( with RV cam)
Thanks
More Turbo
Joined: Mar 2015
Posts: 666
Likes: 5
From: Springfield, MO
Just getting my a/c hooked up recently, I ran into the same concern.
As asked, what is the tstat temp?
When it's idling in park on a/c max and the temp rises, can you confirm when/if the fan clutch kicks in? Not only by listening but also by feeling the air movement behind the fan.
Once it does the temp should come back down. Not all the way down to the point as if the a/c wasn't on but definitely lower than when it's not kicked in.
For reference - on my recently rebuilt 460 with a 180 tstat and 4 row aluminum radiator when in park idling with the hood open, a/c on max and fan clutch kicked in the temp gauge is between R-M and the thermostat housing reading roughly 180 degrees.
As asked, what is the tstat temp?
When it's idling in park on a/c max and the temp rises, can you confirm when/if the fan clutch kicks in? Not only by listening but also by feeling the air movement behind the fan.
Once it does the temp should come back down. Not all the way down to the point as if the a/c wasn't on but definitely lower than when it's not kicked in.
For reference - on my recently rebuilt 460 with a 180 tstat and 4 row aluminum radiator when in park idling with the hood open, a/c on max and fan clutch kicked in the temp gauge is between R-M and the thermostat housing reading roughly 180 degrees.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
You will run hotter with A/C as the A/C condenser is shedding heat right in front of the rad. One thing you can do if your truck is not fitted is add a heater core shut off.
Otherwise, you may need a higher-capacity radiator.
Otherwise, you may need a higher-capacity radiator.
More Turbo
Joined: Mar 2015
Posts: 666
Likes: 5
From: Springfield, MO
While this will help your in-cab A/C vent output temps, just doing it with no other changes will increase the overall coolant temp.
FTE Legend
Joined: Nov 2015
Posts: 30,876
Likes: 4,115
From: Angier, NC
Adding the shut off valve before I got the AC working did not raise the temp but I am also using a 4 port valve to keep hot water going to the intake manifold as I have EFI exh. manifolds.
When I got the AC working I did see the temp go up just a little because of the heat the condenser puts out right in front of the radiator but the gauge still reads pretty low.
I have a 300 six and run a shroud and a fixed 4 blade fan, no clutch.
Dave ----
When I got the AC working I did see the temp go up just a little because of the heat the condenser puts out right in front of the radiator but the gauge still reads pretty low.
I have a 300 six and run a shroud and a fixed 4 blade fan, no clutch.
Dave ----
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Joined: Jan 2001
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From: Virginia
The factory had specific cooling setups and higher output alternators when the A/C option was ordered. These trucks are getting pretty old and have gone through a lot of owners. Things may have gotten swapped over the years, I would check to make sure you have the proper radiator, the proper fan and the proper pulleys on the front of the engine. It should also have something to raise the idle speed when the A/C is activated.
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Post Fiend
Joined: Feb 2008
Posts: 5,831
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From: St Albert, Alberta
This is a worthwhile modification. Being an 86 your simplest options are a manual valve or one that is engaged automatically in recirc mode.
While this will help your in-cab A/C vent output temps, just doing it with no other changes will increase the overall coolant temp.
While this will help your in-cab A/C vent output temps, just doing it with no other changes will increase the overall coolant temp.
More Turbo
Joined: Mar 2015
Posts: 666
Likes: 5
From: Springfield, MO
Care to elaborate? Always happy to expand my understanding.
By adding a shutoff valve and turning it on so the flow is stopped you are removing a radiator from the system. I did not say the impact would be significant or even noticeable (assuming the heater is off).
By adding a shutoff valve and turning it on so the flow is stopped you are removing a radiator from the system. I did not say the impact would be significant or even noticeable (assuming the heater is off).
Moderator
Joined: Jan 2001
Posts: 56,977
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From: Virginia
I looked at the wiring diagrams for 1986. I think you are correct. They have some exceptions in the diagram notes and the 7.5 liter was one of them.
Post Fiend
Joined: Feb 2008
Posts: 5,831
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From: St Albert, Alberta
When the AC is on or the Heat is off you are not moving any air over the heater core, it is not shedding any measurable heat. Instead, you are just dumping near engine temp coolant back into the cooled coolant from the rad and raising it's temp before it even hits the engine.
Cargo Master
Joined: Sep 2006
Posts: 2,120
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From: Evansville, Indiana
Speaking from experience I would add that having good coolant at the proper mixture is important to the BBF. I had this issue twice and cured both times by by changing the coolant. 1970 LTD w/429ci and a 1976 Thunderbird w/460ci.
More Turbo
Joined: Mar 2015
Posts: 666
Likes: 5
From: Springfield, MO
When the AC is on or the Heat is off you are not moving any air over the heater core, it is not shedding any measurable heat. Instead, you are just dumping near engine temp coolant back into the cooled coolant from the rad and raising it's temp before it even hits the engine.
But I wouldn't recommend installing a bypass to address or assist in the OP's situation nor would I say that it isn't shedding measurable heat. Aside from a leaking core, the only other reason I know of in these trucks for bypassing the heater core is to improve AC temps and Vent temps (when set to Cool since that determines whether air moves through the core). This wouldn't be done if the heater core wasn't having a noticeable impact on the in-cabin air temp even if the blend door is set to Cool.
So I'll retract my statement on it increasing engine temp and just say that I recommend the heater bypass but only for the purpose of improving the Cool air temp in the cab.
