Heater temp spec

[James Morse]

I couldn't find the spec in manual for how hot should the heater be. I'm getting 146F that's really toasty hot but truck runs normal temp by the gauge and I suppose if it's running 190F approx and the core is working nice then 146 sounds about right? (on the '97). It ain't broken that's for sure.

 

[sgtsandman]

It should be about 190. Roughly about the same temperature as the engine.

It also depends on where you are measuring temp. Inlet hose should be engine temp or hot enough that you can’t touch it long.

The outlet should be a little bit cooler but not more than about 10-15 degrees.

If it’s cooler than that, you have clogging issues in the heater core.

 

[James Morse]

No I'm measuring the air where it comes out the center dash vent I have not yet measured in/out hose temps it would have to be the temp of the outside of the hoses.
I think some settings it is running the air past the a/c to dry it first that would make the air cooler, right?
Can I flush the core, sure, but right now it's so hot you can drive in winter with the window open, well, you know what I mean. It will roast you.
Seems to me, if core inlet/outlet were the same temp, it would indicate no heat xfr but I get what you're saying. Big diff between in and out would, on the surface, indicate a lot of heat xfr.
On the other hand if it's running freely thru it then core should come up to temp and stay there with only minor temp change in/out, I think that's what you're saying and I agree.
There can't be zero diff in/out or there would be zero heat xfr.
Probably also depends what is ambient temp, I measured it with outside temp about 38F.
Thanks and looking forward to add'l comments.

 

[Curious Hound]

I would say that the air temperature you’re measuring should be fine. Fan speed will have an effect on that also. It may read a bit higher if you measure at the center defrost vent. That’s probably the shortest distance from the heater core. Therefore, least amount of loss in the ductwork.

 

[James Morse]

OK thanks, I'll measure there.
I was running fan on high.
Yes I'm completely happy with the temp like I say it will roast you in short order. The '99 runs about 135 after core flush, I think that's the best I'll bet, which is good, but 145 is better.

 

[sgtsandman]

you are correct on the A/C running on certain settings. Before a certain year, it was windshield only, windshield and floor, and obviously the two A/C settings. After a certain year, they added the dash and floor setting running A/C as well to remove moisture in the cabin air.

 

[Curious Hound]

you are correct on the A/C running on certain settings. Before a certain year, it was windshield only, windshield and floor, and obviously the two A/C settings. After a certain year, they added the dash and floor setting running A/C as well to remove moisture in the cabin air.

I was forgetting about that.

 

[James Morse]

so there's one of the settings where it doesn't run thru a/c right?

 

[sgtsandman]

so there's one of the settings where it doesn't run thru a/c right?

Straight dash vents or straight floor vents for sure. I think your's is old enough that the split floor and dash vents probably won't engage the A/C. The only way to be sure is to set it on split and look to see if the A/C compressor cycles. If it doesn't, your's isn't setup to run the A/C that way.

 

[RonD]

+1 ^^^

As said panel only or floor only = no AC compressor, also OFF, lol
Any AC or Defrost also panel/floor combo will have AC on

Heater hose coolant should be about 185degF or so, after 5 to 8min engine run time
Then you have outside air temp ???
And then AC, if its on, which is 40degF approx., which actually can warm up 32degF air, lol


So you get 146F from air vent
What was outside air temp at the time?

 

[James Morse]

Thanks that makes sense and yes I would know from the a/c kicking in or not, good point.

You really do want the defrost air dry, fogged up interior windshield is a real drag.

Outside was 38F.

Didn't measure heater temp at center defrost yet. I was running panel/floor combo so a/c must have been involved but its 40 about equal to outside temp so probably no huge impact.

 

[sgtsandman]

Thanks that makes sense and yes I would know from the a/c kicking in or not, good point.

You really do want the defrost air dry, fogged up interior windshield is a real drag.

Outside was 38F.

Didn't measure heater temp at center defrost yet. I was running panel/floor combo so a/c must have been involved but its 40 about equal to outside temp so probably no huge impact.

My 1998 didn't have A/C, so the fogged windshield issue was a real thing. It took a lot longer to clear the fog up not having it.