Something on my Chevy Truck has me a bit baffled,,, 16 Silverado, 1500, 5.3 4wd. Temp gauge shows it is running where it is suppose to ( 190/210f), and the resivor is where it should be cold and hot. Now the heater blows air that is pretty much outside air temp untill you get up around the 80 degree mark on the read out. Any ideas Im thinking thermostat but I have been wrong before
OK gear heads
- Thread starter skeets
- Start date
I had a plugged heater core once.
Engine ran at correct temperature, just not much heat.
Engine ran at correct temperature, just not much heat.
Yep, probably thermostat. Shouldn't open that soon. On all of my vehicles, I don't get any heat until I'm almost up to operating temp. If the t-stat isn't open, water isn't circulating, and if water isn't circulating the heater core doesn't get any heat.
Lil Foot
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1979 B7100DT Gear, Nissan Hanix N150-2 Excavator
Had a Dodge PU with a 318 that had a sticking coolant valve (the valve that controls how much hot water goes to the heater core) that had the same symptoms.
Another possibility to throw out there is a malfunctioning blend door actuator or a foreign object that is preventing the blend door from moving.
is this 80 degrees on the engine temp gauge or 80 degrees on the hvac controls?
newer vehicles will set a check engine light and P0126 or P0128 code if thermostat is stuck open/opens too soon/rubber seal on it deteriorated.
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It sounds like you have automatic HVAC. I am assuming that your engine is warmed up and you get no heat until you dial up past 80°F.
There are 3 sensors that control the heat or cold output.
In-car sensor: Located low in the dash. If this sensor is colder than your setpoint, it will boost the heat output. It could be cold outside, but the car interior is warm due to sun load. In this case, the sensor would cause the heat output to back off or actually provide cool air.
Sun Sensor: Usually located in the center of the dash. If high sun load is detected, this will cause the heat to back off. If dark outside, heat output will increase.
Ambient sensor: Located in front of the A/C condenser. If ambient is low, heat output will increase.
The combination of all 3 sensors is used to calculate the desired output air temperature. If you are running in AUTO, the blower speed and mode will automatically adjust to get the trucks interior temperature close to your setting.
I have been in high elevation areas where the sun is powerful, but ambient temperature is around freezing. At my setting (~70°F), the system will run in bi-level or even vent mode.
Some people with automatic HVAC confuse the temperature setpoint with the air outlet air temperature. The setting attempts to control the interior temperature. Outlet temperature, blower speed, and mode are automatically adjusted to achieve your setting.
It is possible that an ambient or in-car sensor open circuit could cause low heat output.
Disclaimer: I worked in automotive HVAC engineering for about 28 years.
Hope this helps.
Retired 3 yrs ago. A good chunk of the 28 yrs was with Ford.Not to be a smart ass, but I gotta ask
how long ago?
GreensvilleJay
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BX23-S,57 A-C D-14,58 A-C D-14, 57 A-C D-14,tiller,cults,Millcreek 25G spreader,
Cars were better before cheap 'computers' came out ! heater had a CABLE attached to a LEVER, dial sad 'cold---hot'. EASY, Easy to fix....
skeets, can you give more info? Is it not heating until the temp setting on the HVAC controls is set above 80 degrees?
Well heres the deal, since I bought the truck I always run the cabin temp around 70 or so. According to the digital read out on the dial. And when the temps droped it would warm. Defrost floor and cabin nice air. Now as of the last week or 2, the air blowing in to the cabin is maybe a bit warmer that out side air but if so, not by much. Now adjusting the temp up one degree at a time , the system will not blow warm air untill it gets around 79 or 80 , again according to the digital read out on the control knob.
AC works like a champ. knock on wood, so I dont think it is in the mixing door, though maybe mice or a chipmunk got in somehow and did their thing. The engine comes up to temp fine, it has gotten to temp quickly since it was new. Now I just thought if the control is turned to max, it will blow hot air. So there is no inbetween so to speak. Either hot or cold, kind of like some girls I use to know
AC works like a champ. knock on wood, so I dont think it is in the mixing door, though maybe mice or a chipmunk got in somehow and did their thing. The engine comes up to temp fine, it has gotten to temp quickly since it was new. Now I just thought if the control is turned to max, it will blow hot air. So there is no inbetween so to speak. Either hot or cold, kind of like some girls I use to know
I would suspect the blend door motor…
Is it a dual zone system? (Can driver and passenger set their own temp?)
Could also be just a software issue, or less likely but still a possibility it could be the control module…
Is it a dual zone system? (Can driver and passenger set their own temp?)
Could also be just a software issue, or less likely but still a possibility it could be the control module…
What is the ambient temperature when you are noticing this?
What is the sun condition- sunny, dark, cloudy?
What is the temperature of the cabin? Is it (subjectively) colder or warmer than your desired setting?
Is your ambient temperature display on meter or screen correct or reasonable? Same sensor feeds ambient display and auto HVAC software.
The ambient and in-car sensors are thermistors. You can read the sensor resistance and convert it to a temperature, they are all the same.
The sun sensor is a photodiode. The signal changes with sun intensity. The sun sensor also feeds the auto headlights. Are they working OK?
I think most OEMs program a specific sensor value in case of a sensor failure. I know for ambient, a value of 50°F is used in that case. A bad sensor will most likely not show up by the check engine light, but a scan tool, like CONSULT, can find it.
First thing to do is check sensor connections. Sensors rarely fail, but open connections are common in the warranty data.
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RCW
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BX2360, FEL, MMM, BX2750D snowblower. 1953 Minneapolis Moline ZAU
Ford - guessing it is dual control.
Guessing same as my ‘17. My 2013 was too, although that was last year of the series. ‘14-‘17 were the same series.
Skeets,
First check the ambient and in car sensor electrical connections.
This scan tool should meet your needs. It can monitor the HVAC system.
GM has has issues on the blend doors and their actuators. GF's acadia, constant battle with them. Constantly. Neighbors silveraydo, same issues