Thermostat temps

[JustEmptyEveryPocket]

1 hour ago, AZJeff said:

116* F

At least its a dry heat? 

[Manche757]

I asked the initial questions about the correct thermostat and whether I should replace a working water pump prior to having new a/c installed on an 89MJ that never had a/c previously. I had a mechanic install a/c without replacing the water pump or thermostat. Not long after that, leaks and rattles were followed by replacing the water pump and thermostat with a 195 'stat. I had the non-leaking heater core replaced with the a/c install because it is a big job getting to it. The heater control valve had never been removed previously which is a good thing. Otherwise, the heat would be on in the same plenum box as the a/c core. Winter came. 195 thermostat in place; good heat expected, right? Nope. Luke warm heat. We get winter but down in the 20s F is cold here. A next step might be to replace the heater control valve with the thought that either because of age or poor original  design, water flow may be restricted. For me, optimal a/c is more important than optimal heat. I will probably leave well enough alone. 

 

[eaglescout526]

3 minutes ago, Manche757 said:

Nope. Luke warm heat.

 

I feel this is a common problem after installing AC into a non AC truck. The only thing I can think of that I didn't do was clean and prep the heater core before installing everything. Course I cleaned out the inside of the box where the core is but not internally of the core.

[Manche757]

20 minutes ago, eaglescout526 said:

The only thing I can think of that I didn't do was clean and prep the heater core before installing everything. Course I cleaned out the inside of the box where the core is but not internally of the core.

I had the core replaced more out of concern for leaks in 30 year old metal than for concern for interior rust or scale that would act as insulators and retard heat transfer. After your comment,  i suspect that heat was not great when the trucks were new because of under sized heater cores. 

[eaglescout526]

1 minute ago, Manche757 said:

i suspect that heat was not great when the trucks were new because of under sized heater cores.

 

Possibly but heat was fantastically blistering in the winter for me so I'm not sure why adding an evap would change the temp of the heat from the core.

[Minuit]

I am one of the few people who actually un-deleted his heater control valve. I noticed pretty much no difference in heater performance, but a small but significant improvement in A/C performance. The heat in my truck has always been pretty damn good considering the absolutely minuscule heater core. Certainly more than enough for what passes for winter in TN. Definitely not "luke warm" - my heater vent temp clocks somewhere in the 130s at the vents when warmed up.

 

The heater control valve piping does have a few places where an air bubble might get trapped. Does the heat get any better when the engine is above idle?

[Manche757]

8 minutes ago, eaglescout526 said:

 

Possibly but heat was fantastically blistering. 

We have a conundrum.

[eaglescout526]

Just now, Manche757 said:

We have a conundrum.

This was before AC. 

 

Now I will say when I turn both sliders to heat, I get heat out of the bottom floor vent and it is really warm. But when I slide to "Vents" the heat gets cold and would be my guess of cold air coming in and cooling off the core. But even then before AC it wasn't a noticeable issue. Sometimes reading the owners manual on this goes a long ways but I still never remember what is said in the book lol. 

 

I havent deleted the valve and I remember checking one cold morn to see if it was functioning and it was, just heat would come out luke warm from the vents but hot from the floor. I'll remember to clock the heat temps in the winter.

[Manche757]

8 minutes ago, Minuit said:

The heat in my truck has always been pretty damn good considering the absolutely minuscule heater core. Certainly more than enough for what passes for winter in TN. Definitely not "luke warm" - my heater vent temp clocks somewhere in the 130s at the vents when warmed. Does the heat get any better when the engine is above idle?

It never gets as hot as both of you describe. I don't intend to throw more money or time at it.