Temperature Control Knob

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

So, I just replaced my thermo housing, thermo, radiator, water pump, and blower motor resistor pack. I've done work on my coolant system a million times in the past. I took the cap off the reservoir as I always do to let it run at full on hot. It got warm and now the temp is either warm or cold. Heater core lines are both hot. My temp gauge reads in the middle, just slightly below actually. I have a couple of questions I can't seem to remember:

1. What temp should the upper and lower radiator lines be?

2. The temp control knob (from left to right; fan control, system selector, temp control), should it have a slight clicking feel to it as you turn from cold to hot? Any resistance at all?

I'm not sure what to check next. While driving it is pretty cool, not cold, but cool. On 3, it is warm. It is all over the place. The thermo is in right. If the temp control knob is not broke, then all I can think if is air lock and I will need to bleed out the air some more I suppose.

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

So now, I am stumped. I am backtracking a bit now. I let it run this morning for about an hour. I massaged the lower and upper tubes on the radiator. The needle on the dash is just a smidge below middle. The heater core lines are about where they should be. But I am still getting cool air blowing in the cabin with the heat on full and fan on full. Any input from anyone would be great. I am draining the coolant now and am going to refill.

WWDiesel · **Posted:** Fri Jan 05, 2018 1:51 pm

Could be the Heater Blend Door actuator not working as it should! Others have had the same problem...
It operates a door that blends cold air with hot air depending on dash knob setting to give desired air temperature!

https://www.factorychryslerparts.com/pr ... 382AA.html

Item 15 on this illustration. (click to enlarge)

flash7210 · **Posted:** Fri Jan 05, 2018 2:02 pm

Quote:

2. The temp control knob (from left to right; fan control, system selector, temp control), should it have a slight clicking feel to it as you turn from cold to hot?

Yes, there should be slight clicking.
If you turn the key on (engine off and radio off), listen carefully while turning the temp control knob. You should hear a faint buzzing as the motor moves the door flap.

Is the blower pushing air out the vents at all speed settings?

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

Yeah air is coming out as it should on all settings (1-4). I just drained all the coolant a second time. The only thing that is strange to me is the temp gauge on the dash. It is just a hair below the middle. Also, when it is at idle, the temp is cool. When I raise the RPMs to 2500 it gets warm.

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

With the engine off and radio off....I can hear a slight buzzing sound. I can feel a difference in the temp control at cold and hot.....cold is very cold....and hot is luke warm.

Another piece of the puzzle:

When i raise the RPMS and see the fan kick on, the temp gets very warm. But when the fan kicks off and lower the RPMs it goes back to cold. I am starting to wonder if I have a fault thermostat.

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

Last update. I just drove it around for about an hour....all the way down to Hamilton, Ohio and back. Some other findings:

1. On 1,2, and sometimes on 3....I get heat. On 3 and 4 it blows cold air.
2. I checked the upper and lower hoses again after an hour trip. The upper was hot (180ish). The lower was warm (120ish).
3. Temp gauge stays put the whole time just a small bit under the middle.
4. About a 15 degree difference between the heater core temps.
5. Everything in the dash is working as it should. I can get all fan speeds, all positions, and I can hear the motor working on the blend door.

Anyone else have any ideas?

WWDiesel · **Posted:** Fri Jan 05, 2018 9:12 pm

It is most likely the rotary temperature position switch is bad not sending the correct signal to the blend door position actuator or the blend door actuator itself is defective! :roll:

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

You think? Even hearing the audible humming of the motor moving the door?

r1perk · **Posted:** Sat Jan 06, 2018 11:42 am

I would try back flushing the heater core. It is cheap and easy.

WWDiesel · **Posted:** Sat Jan 06, 2018 12:40 pm

Lima.Charlie wrote:

You think? Even hearing the audible humming of the motor moving the door?

But is the blend door actually moving to the correct position???
IFyou got good hot coolant flow through the heater core, which I believe you stated you have checked and said everything appears to be normal.
If this is the case, then the problem has almost got to be in air temperature control within the HVAC box... :roll:

You are either not getting proper heat into the heater core, or the air flow control through the heater core is malfunctioning...not a lot else can affect the outcome... :juggle:

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

What's the temperature on the hoses for the radiator supposed to be?

Thanks for your advice.

WWDiesel · **Posted:** Sat Jan 06, 2018 4:13 pm

Lima.Charlie wrote:

What's the temperature on the hoses for the radiator supposed to be?
Thanks for your advice.

The upper hose coolant inside the hose leaving the thermostat should be ~176 deg.s F if the thermostat is functioning correctly and you are at normal operating temperature.
The outside of the hose will be a little less depending on ambient air temperature.
The bottom hose temperature will be much cooler depending on the ambient air temperature amount flowing through the radiator and exchange rate cleanliness factor of radiator internals.
So it's hard to say what bottom temperature would actually be! :roll:

Measuring the metal temperature of the inlet of the heater core pipe, if you can get to it to measure with a thermo gun, should be real close to thermostat outlet temperature I would think.
The outlet pipe should be less depending on how much heat is being exchanged with the air flowing through the HVAC!

But I am no thermodynamics engineer and there may others on LOST who are more qualified to answer your questions like TURBO-DIESEL-FREAK. :wink:

r1perk · **Posted:** Sun Jan 07, 2018 9:21 am

If there is very little flow through the heater core the outlet will also be at a lower temp.

That is why I recommend back flushing the heater core.

Lima.Charlie · **Joined:** Sun Dec 27, 2009 11:02 am **Posts:** 376

I'll try this week. We are still in single digits too. I'll follow-up then.

Temperature Control Knob

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