Heat blows cold when it's cold outside

[mhorn0817]

2014 Silverado 1500 with 172k

 

When it is cold outside, roughing 38 degrees and lower, the heat will blow cool. After driving a little while, it will eventually blow out some heat, atleast until the truck comes back to an idle. At the same time, the truck will run cool between 165 - 185.   When it's warmer outside, the truck will have no problem blowing out hot air and the truck will run at 200.  Curious if anyone thinks this is a thermostat issue or water pump issue or a combination of both?

 

Also, I have the temperature sensor issue that comes and goes. I've replaced the sensor 2 times and the problem still comes and goes. Truck stays at 160 and fans run on high.  Now the heating issues happens no matter if the temperature sensor issue is happening or not.

 

Just seeing what everyone's thoughts are on what could be causing the problems.

[CamGTP]

If it's running that cool when the fans aren't running, replace the thermostat. Then it should run at just over 200 degrees all the time.

 

Could also be a blend door issue if it doesn't blow warm air at all even if the temps are somewhat warm. Even at 160-180 degrees, there should be hot air coming from the vents.

[mhorn0817]

Yeah, the heat only acts up when it's cold outside, 38 degrees and below. Also the truck won't reach 200 degrees temperature.

[mikeyk101]

Sounds exactly like my thermostat problem last winter. It struggled to get to the 210⁰ mark on dash gauge. But the dash gauge is an idiot gauge. It will show 210⁰ when coolant temp is between 185⁰ and about 225⁰. If it isn't reaching the 210⁰ mark, you are below 185⁰ and will not get the heat needed to stay warm in the cab. 

 

So replace the thermostat and ist actually pretty simple to do. But my advice is to stick with OEM. Last year, I replaced mine with a Motorrad 194⁰ to get ahead of the heat in warmer weather when towing. It failed after several months and coolant began running hotter than it should, bordering on overheating. I replaced it with a OEM 194⁰ thermostat instead of the OEM 207⁰ thermostat. It's run well ever since.

[richard wysong]

I agree change the Tstat, You may also need to flush the heater core because as Cam stated it should have heat even at 160

[mhorn0817]

Sounds like a plan. I'll do a coolant flush and replace the thermostat.  Only problem is I do not see any OEM thermostat available online, guess I'll have to try the dealer.

[richard wysong]

You may have to flush the heater separately from the rest of the cooling system. Disconnect the heater hoses and use a garden hose, flush forward and reverse

[kickass audio]

I am voting the thermostat is bad or coolant level is too low. The 2014 I had had went through 3 radiators for the micro cracking at the brace near the side of the rad and would make my coolant level drop after about a month of driving. There was a service bulletin for this and a newer style thermostat was installed along with a new radiator.

 

My old 14 would hit the 210 mark but after warming up it would drop down a tick below 210 and stay there. When I looked at the thermostat after changing it out, it had a very slight bow on the thermostat within the housing and it was allowing coolant to pass through just slightly when it should have been totally closed off.

 

Something you can also do to check the heater core for a potential plug would be to get the truck warmed up and grab the hoses going to the heater core. one should be very warm and the other will be a bit cooler as it passes air through with your vents on trying to heat the cabin. If one is barely warm at all and the other is screaming hot then you have a clog in the heater core and could use a flush.

 

I would start with a new t-stat and while you're at it if you haven't due to it's age, change the coolant out completely as well.

[CamGTP]

OEM thermostats may be hard to come by right now. If you choose to go with an aftermarket I'd suggest the Napa Thermostat. I've been running one for the past 4 years without any major issue. The first one was sticking open a little and caused it to run a little cooler so I was able to exchange it under warranty no problem.