Like the title says, is there a foolproof way to tell if I need a heater treaters? I looked at the blend door motor yesterday, it does move when the temp knob is turned but I can't really tell if the door is moving at the same rate. Am I going to have to take the motor off and remove the little piece just to see if it's cracked?

 I'm asking because I like some others on here have heat, it's just not as hot as it should be at the vent. 

 A year or so ago I replaced the heater core and a/c coil and inspected the door seals. That should all be good. Seals were in good shape and everything seemed fine. Since then (and before) I just don't get piping hot air coming out of the vents even with the engine twmp gauge reading 190°. So I figure it's time to check the little plastic thingy in the blend door.

 Any thoughts?

 Wish I had a laser thermometer to check heater hose Temps. I know one gets pretty darn hot, can't hold onto it. The other is slightly cooler. You can hold onto that one.

Typically when the plastic coupler breaks then the motor just keeps turning and never stops. The last one I went to service it would turn both ways and never stop but the air temp will not change from hot to cold or visa versa. As for heat issues two thing to check both hoses should NOT be equally hot. If the heater core is performing good then the one hose going to the steel tube (not going to the head) should be considerable cooler than the hose from the head. So if the hot side is 195*F roughly while the truck is running the cold side could be as low as 100 to 120*F returning back to the water pump. This show good heat transfer to the air. If both hoses are equally hot then the heater core is plugged internally with debris or externally plugged at the evaporator.

 

 

The other one I found is if the evaporator core is plugged up with debris on the face then heater performance will suffer. Like the photo below I replaced the heater core, then power washed the evaporator core removed all the debris and the customer complained about being cooked to death in the cab. 

 

 

When all is working you should see about 160*F to 170*F out of the center vent on high fan and temperature knob over to full hot. 

DT, couple options at HF. Very handy to have.

2 hours ago, Doubletrouble said:

I looked at the blend door motor yesterday, it does move when the temp knob is turned but I can't really tell if the door is moving at the same rate. Am I going to have to take the motor off and remove the little piece just to see if it's cracked?

 

If you have never changed out the plastic interposer that connects the blend door motor to the blend door, I would just do it.  When I replaced mine several years ago, I could not see a crack in the interposer, but it was worn and it was the problem.  

 

Trying to diagnose a cabin heater problem by checking the temperature of the heater hoses is not a conclusive solution.  If the blend door is stuck in a mid-range position, the symptoms will be the same as a partially plugged heater core.

 

- John

 That was my thought @Tractorman, not discounting at all what @Mopar1973Man stated. I'm thinking the interposer may be worn ir maybe a slight crack to where it doesnt quite close the door fully allowing a bit if cold air to mix with the hot air. Last time i checked (ill check again today) the vent temperature was around 140°F. A 20°F difference from what Mike shows could be explained by my theroy i believe. When i pulled the HVAC to chenge the cores i cleaned everything before reassembly and checked all the gaskets and seals.

 I think this winter i will be oredering a winter cover as well to help keep the heat under the hood during the colder days.

You could install a 6.7L thermostat that is 200°F. @pepsi71ocean been running one for quite some time.

3 hours ago, Tractorman said:

If the blend door is stuck in a mid-range position, the symptoms will be the same as a partially plugged heater core.

That's one I've never had either the door is stuck full hot or full cold. Mine I've had it apart and glue the plastic coupler back together with super glue being I was short on time. I needed the truck right now type moment so its still working yet.

 I went ahead and ordered the heater treater for the truck. I figure if it isn't broke or cracked yet it will be eventually. Still considering the winter cover from Genos as well. Today it was 30°F and the heat coming out just don't feel as warm as it should. I didn't have a thermometer to take a reading. I feel that it should heat you out of the cab. The cab isn't that big. 

Yesterday mine failed. I'll be looking into a heater treater kit too. Got too hot in the cab dialed it back to full cold and roasted out for few miles. Turn it off and on to control temp the about hour down the road it caught up again. Yup I need to get one.

 @Mopar1973Man, is that the one that was glued before in a time crunch?

 I'm curious to see what shape mine is in. I don't want to pull it apart until I get the heater treater kit though. Kinda need the heat around here now. 

 Still haven't pulled the trigger on the winter cover but getting close.......

Just pull the carpet back and pull the blend door motor. Now you can see the the shaft coupler. You can manually move the blend door shaft. You don't need to worry I've done this for clients until the kit comes.

 Ordered the winter cover today. They are now on backorder until 11/25 so I figured I better not wait any longer.

I believe somewhere on this site is @Mopar1973Manwinterfront. Easy to make and nearly no cost. 

@Royal Squire, I made some inserts for the 4 grill openings last year. They helped a little I think. (Might have been a placebo effect also) but I wanted to try an actual "like OEM" type winter cover. I don't really haul or tow much, especially in the winter so I need all the help I can get to maintain heat under the hood.

Just ran to Boise, ID as I type this this morning it's +10°F and helped quite a bit keeping the IAT above 80°F through most of my travels. 

I see @Doubletrouble. Thought I would try to save you some money 💰 

 Received the heater treater kit yesterday. I'll be installing it sometime in the next few days.  I've been under the weather since Friday so I haven't done much of anything since. 

 From the looks of the kit and the instructions it seems pretty straight forward. Only trick is the rear screw on the motor itself. I'll need to pull back the mat (no carpet in my truck) and find my right angle screwdrivers. Haven't used those in quite a while. Lol

On 11/13/2022 at 9:40 AM, Mopar1973Man said:

When all is working you should see about 160*F to 170*F out of the center vent on high fan and temperature knob over to full hot.

 Now @Mopar1973Man, is this after a drive to thoroughly warm up the engine? Also, was there a winter cover installed at that time? Outside temp? Just curious of the variables involved with this measurement. 

4 hours ago, Doubletrouble said:

Only trick is the rear screw on the motor itself.

 

To make the rear screw installation easier, I used a longer screw with a spacer (can't remember the length).  This made the head of the screw more accessible for starting the threads and for keeping the tool driver on the screw.

 

I don't think I would worry about the actual temperature coming from the vents.  You will know if it is fixed.

 

- John

 The heater treater kit actually comes with a replacement fir the rear screw. It's a stud, screw threads on one end to thread into the plastic and machine threads on the other with nuts to install.

 Installed the heater treater today. I'm not real clear on the indexing of the stepper motor though. 

 I did find that the oem coupler was cracked. Once I got the new piece in I drove the truck for about 10 miles to test heat output. It was not impressive. Dash gauge showed nearly 190° but my digital thermometer only showed 108°F at the center vents.

 I don't get it, I've never had issues like this with heat. 

 

40 minutes ago, Doubletrouble said:

Dash gauge showed nearly 190° but my digital thermometer only showed 108°F at the center vents.

Umm that's about 183*F to 185*F on the gauge too cold. The needle should be just past the 190*F mark normal operation on a 190*F thermostat. So if the heat is poor pull the blower down and inspect the evaporator face for debris. Then check the temperature of both hoses one should be considerably cooler if the heater core is working good. If both equally hot then the heater core is not exchanging heat into the cab because of poor flow of coolant.

 

I've got a 2014 Ram to look at soon for the same problem weak heat from the vents. Most likely a plugged heater core being the coolant has not been changed since new on that truck.

 

REMEMBER - Coolant should be changed on a regular basis. Max of 3-4 year period. Do not attempt to reach 100k miles on these extended life coolants. More times out of ten the coolant has broke down and the pH level is acidic and eating everything. This is what causes the scale blooms in the radiators and heater core because the metal is in solution it will solidify as it cools hence the build up. This is not from using city water, etc. I debunked that long ago since my truck has 454k miles and ZERO blooms in the heater or radiator even using CREEK WATER and WELL WATER! I've never used distilled water ever. It about keeping the coolant fresh and pH level correct!

 

385K miles no scale build up or rust.

 

I'll do that tomorrow. Gonna be leaving for the inlaws soon for dinner. I'll report what I find. Heater core was changed about 2 years ago, hvac was cleaned out at that time, seals all looked good as well. 

 Just want to figure this out before it really gets cold here.

 I also changed the thermostat 2 years ago as well. 190° stat, watching the gauge it seems to open just past the 190 mark and drops fast til it closes again. It cycles up and down till all the coolant is heated