Getting off the original topic some, but the heater core always has water going thru it independent of what setting you have on the control ****......

The control **** just opens or closes a 'door' that controls the amount of air that passes thru the core.

I've got an aftermarket water temp gauge and I tapped into the heater hose line (inlet side) for the sender.

I get the same temp reading no matter what my control **** is set to. If it did stop the flow of coolant to the heater core, I would have different temp readings all the time. There would also have to be some sort of bypass hose setup to allow the coolant to continue to flow back to the engine or the rad. I've not seen a setup like that.

 

We are a little off topic but....

For your test.... HUH????

Yes your right the block and coolant does maintain 198 degrees +/- up to 20 degrees depending up on temperature & quality of thermostat that is installed in you engine. Which the coolant temperature is what your experiment tested vs the heater core or air temp. Do you not have a temp gauge on your dash to tell you that? If you check both sides there is always a difference in the coolant temperature after it leaves the core do to heat exchanging. How your core works basic princiable is that it's heating the air up and the air is cooling it off. Thats why they say to run your heat even in summer if your engine is over heating. If your thermostat is open and you have coolant it will help disapate some of the heat. "think of it like a second radiator"

On my Triton the inlet for the heater core appears to be loacated at the rear of the block and it dumps it back in to the thermostat housing. Some vehicles pick it up at the water pump and dump it at the thermostat. It is not part of your engine cooling system! If your heater core or heater hose bust, you can cut the high side and simply place a bolt in it with a hose clamp on it in the one closes to the block to plug it off untill you can get it fixed. It will not change nor damage your cooling system in anyway, but you will not have heat. No extra pressure is added to the cooling system as it is not inline with cooling system, it's only a secondary port for coolant to travel when you allow it to. That is why if your engine thermostat is stuck closed your engine will over heat and you may or may not have a heater.

For the airflow temp of you HVAC the formula is
GPH + CFM + incoming "or outside" AIR TEMP
Which means that the coolant GPH (Gallons Per Hour) flow through the heater core plus the incoming air temp & cfm of air that flows through the fins that determines how warm/cool the heater core fins are able to maintain. If outside air is above 40 degrees you will never get the vent air below 40 degrees even with AC on as that is the temperature of R-134A, how ever on older vehicles R-12 is 30 degrees. Since the outside air temp is not the same every day that is why you can not set your system and have a constant 75 degree everyday.

Consult your owner’s manual or Chilton’s or Haynes. They all explain how you HVAC works and how to use it.

To test the air temp coming out of your vents
(Due to the changing variable of the outside temp you will not get the same reading on the same vehicle everyday but there will always be a difference in the settings if HVAC is working properly)

1. Start with the motor warmed up and the Temperature control on low "cool", the mode selector on Vent & Floor, and the fan on high, after 2 mins. take thermometer reading.

2. Then move Temperature control 1/4 of a turn to the right while fan is still on high, after 2 mins. take reading.

3. Then move Temperature control 1/4 of a turn to the right (now at 1/2 position) while fan is still on high, after 2 mins. take reading.

4. Then move temperature control another 1/4 of turn to the right, (now should be past the blue and into the red), and after 2 mins. take reading.

5. Then turn another 1/4 of a turn to the right (now wide open) and after 2 mins. take reading.

Note: On older vehicles the Temperature control is a slide control instead of rotary so simply substitute the rotate **** with slide lever. On state of the art climate control systems they have a computer controled thermostat and will not have a manual temperature control **** or lever.

You should have 4 different air temperature readings, you can leave it in each of the three middle positions for as long as you want and it will still never give you the same as a wide open or closed reading. If it does then you have a stuck control valve or a vacuum problem that needs to be addressed.

PS I grew up helping in my dads Heating and Air conditioning shop. This is how a certified HVAC Tech will test your system to begin diagnosis "he might use his hands instead of thermometer". Because I grew up around it then to me it seems like basic grade school physics.




No there is not anything that does that. Air flow is controled by your fan speed.

Fan speed: controls CFM or amont of air allowed to pass by by HVAC fins and into the vehicle
Temperature control: Controls the amount of coolant to your heater core. (even with AC on you can open this and it will blow hot even in winter)
Mode Selector: Does open, close, or switch a door that determines which part of the duct works recieves the air flow if any. (IE Vent & Floor, or Floor, or Floor & Defrost, or Defrost.) But when it is in "Off" it shuts off the coolant flow to the heater core as well as the Air entering the duct work.

Edit:
Later added
Note: Some vehicle makes even have a manifold heater. Which generally is a line that runs from the water pump and runs thru the exhaust manifold several times, then through the heater core, and then to the radiator. Since it is not reliant on the thermostat to allow water flow and it captures heat from the exhaust manifiold then it both helps keep engine temps down by cooling the exhaust while allowing hotter coolant to enter the core. Plus the exhaust warms up with in seconds of the engine running so it began to blow heat as soon as the exhaust warmed up vs. waiting on the block to get warm enough for the thermostat to open. Down side since the ports were built into the exhaust manifolds if you put headers on them then you had to plumb a direct line from the pump to the core and wait for the block to warm up like everyone else then. Also they are expensive to manufactur and because of the high temps and people not keeping a proper coolant mixture manifold ports and heater cores were prone to calcium build up eventually plugging them up. Today if I had one I would use bottled water and high end antifreeze.

 

There is NOTHING I dislike about mine…

 

I wouldnt either if I were you!!!
Even if it ran like crap and nothing worked right on it... then it would look good while it was not doing it anyway!!!

The exterior on mine is still bone stock so the thumbnail of my Motor Art in my sig is more than enough to see of it! LOL

 

All I'm saying is that I think coolant runs thru the heater core all the time. Thanks for the lesson in how to adjust the heat however.... I always wondered what all those ***** did....

The temp gauge in the dash is worthless for telling you the fluctuations of engine temp. It's just an idiot light with a needle on it. Even with a functioning thermostat, the engine can run hotter at times, like when towing a trailer up a 6% grade in 90* weather...

That's why I installed some real gauges on the A piller. My water temp got to 210* on the 6% grade while the dash gauge sat in the same spot as it does when the coolant temp is only 150*.

So, basically what you are saying is that if my heater core ever goes bad, all I have to do is set my temp control to full cold and that stops the coolant from going thru the core?? Then why bother having to splice the heater core hoses together when that happens??

Anyway, don't want to start a whole debate on this....... It's just not that big of a deal and it's totally off base from the original topic anyway! I might even be totally off base here, but I just don't see how the coolant stops going to the core, yet my temp sendor (in the inlet heater hose line) shows the same temp regardless

Mitch

 

I bet the instructions told you specifficaly to put it on that side too. Wonder why that is? I guess it's possiable they put 2 different controls to handle the air flow.

psst.... click here and read the Case/Duct systems section. GM & Ford "Case/Duct systems"

Yep like I said stock thermostat is 198* and temp will vary plus or minus 20*. Though 150* is a little cold for proper complete combustion on most vehicles.
With a 60* difference under that small of a load, I'd put my money that you'll find possiably a partially stuck thermostat, or a bad head gasket, or a cracked head. Mine doesent get to 210* and thats in summer 104* index and pulling a flat bed trailer of logs 4,XXX lbs + around the Ozark Mountains or up and down Ozark Hills on the interstae at 80 MPH. I'd check the thermostat, cheapest and most likely. Once fixed you'll find more power and better gas mileage. Just a heads up.

No ofense but I live in the Ozarks...6% grade is flatter than my roof, thats cheese cake for these parts of the woods. For us Hillbillies we would think we were driving in Kansas! If you see a warning sign around here that says steep grade. You'd better be either getting a run or checking your breaks depending on wich way your going because they are NOT kidding. LOL

 

I don't think we are.

Since when does the F150 use a coolant flow valve instead of a temperature blend door? There may be an actuated coolant shut off valve for full cold (or just max A/C) but that's only on/off operation.

Using a coolant control valve would lead to obnoxious temperature stratification since the inlet side of the core would be way hotter than the outlet side and mixing is pretty minimal after the heatercore.

 

Heater Core Basic’s 101:

1. Water is always running through the heater core. The only way to stop the water from running through the heater core is to disconnect the hoses and by-pass it.

2. The heater core is a type of heat exchanger in that its function is to dissipate heat from the coolant running through it. This serves two functions, first it helps and/or assists the radiator in dissipating heat from the coolant and second, by using variable speed fans and ducting it can route this dissipated heat into the interior of a vehicle.

3. The “heat” range or selector **** in the interior of a vehicle does NOT control how much heat is dissipated from the heater core. The heat dissipated from the heater core is solely a function completely dependant on the actual coolant temperature.

4. The “heat” range or selector **** only controls how much “outside” air is mixed with the “heated” air being dissipated from the heater core. Think of it in these terms, not necessarily how it is done but very basic, you have a butterfly valve in the ducting. In its fully closed state it allows no outside air and thus all the air is completely from the dissipated heat from the heater core. As you open this valve you are mixing in outside air while cutting off some of the dissipated heated air from the heater core.

So, in conclusion, water flowing through the heater core will remain constant regardless of any interior **** settings as well as the heat dissipated from the heater core will remain constant regardless of any interior **** settings. You can ONLY have water completely flowing through the heater core or NO water at all, there is no in between. You can NOT control how much heat is dissipated from the heater core…

Class dismissed and there will be a test tomorrow…

 

PSS-Mag,

I know I said I did not want to debate this, but I'm going to talk about the temp gauges this time...

When I say the stock dash gauge shows the same needle position from 150* to 210*, I mean when my other gauge shows 150* AS THE ENGINE IS WARMING UP, the dash gauge is already where it will sit for eternity.... When my other gauge shows ~190*, AFTER IT'S WARMED UP, the dash one shows the same exact position as before. The dash gauge is not a resister type of gauge..... It's set to sit in the same position for a huge range of temp variation. My other gauge is a resister type and will show very slight temp changes.

Thanks for the "heads up", but I did not have a 60* temp change on that 6% grade. More like a 10* temp increase. I was pulling in second gear, running about 3500 rpms going 50 mph with the A/C on FULL COLD and only pressing the gas pedal about half way. I was taking it easy, and the truck performs just fine. No cracked heads, or faulty T'stat. I get about 16 mpg on average......

I do agree with 01's assessment of the coolant flow thru the core however....

I'm sorry our Cascade mountain range is as flat as your roof pitch..... I don't know why we have a 14,000 foot tall mountain in that range either............

 

LOL sorry for the mistake on your temps . It threw a red flag so thought I'd share and maybe help out. Glad to know it was exactley as I said it should have been.

It's true that I have not worked on my truck's heating or A/C yet... BUT I still help familys and friends out alot and on other trucks like my brother 97 F150 Lariat as well as the GM's and my jeeps the flow control valves are the most common item that are replaced on HVAC after thermostats, or water pumps. That article says GM and Ford has them but I just replaced one for a friend in his 94 Plymouth Voyager last winter. The auto stores sale them and after replaced "if bad" then the opposite heater hose starts getting hot again.

I won't attempt to work on ACC (automatic climate control) HVAC's similar to what 01' is talking about except they use a combo of fresh and recirculated air combined with coolant flow control to regulater the temperature of the air entering the cabin. I could be wrong but as far as I know that is not an option on any of our trucks they require a series of 6 or more sensors located through out the duct work and inside the cabin and a highly sophisticated circuit board on the back of the drivers controls. Usally is offered on high end luxary cars for and additional $8,XXX or so. I'm 99.9% sure my truck has a very simple more primitave HVAC since there is not a sensor hole in the control panel nor sensors on top of my dash. When I replaced my radio I would have noticed the circuit board immediatley and my buddies and I would have oggled over it for a while and likely played with it to see how it worked, then tore it up in the process.

I said my roof is steeper than 6% grade and a 10/12 pitch roof is indeed steeper than a 6% grade, elevation has nothing to do with the grade. I was just trying to be light hearted I am sorry that you are incapable at this time. If 6% is steep, then it would scare you if you seen what we have to climb just to get our boats out of the lakes.

 

FCV (Flow Control Valve) on wifes 96 Ford Explorer " same interior control panel as my 2000 F-150" as I stated before on many late models it has been relocated to under the dash to both clean up the appearance of the engine bay and save on manufacturing cost. But is NOT easily accessable as you have to remove the dash and the heater core to gain access.
Notice this one is vaccum activated servo that moves the valve to open or close coolant flow as required by the Driver. Some are cable operated. Also notice a pair of pliers is all that is required to remove this one. Mechanic charge on 2000 F-150 "like mine" estimated book time 6.75 hrs. to remove and install. If mechanic charges $20 an hr. total labor $135 + part $15= $150. Actuall estimated time 4 hrs. with noivice experince level + part $15. Thats a lot to pay for a $15 part that you don't even think is there.
Current view is wide open full coolant flow.



Second view is from underneath, view of the arm and lever that the vaccum servo activates. If you wish I can take several pictures to post showing the various positions that it rest in accordance with the T.C.K. (temperature control ****) postions indside the vehicle. Current view is wide open, RED, or hot what ever you want to call it.




In High School the Auto Mechnaics teacher told me in conversation one day that the automotive heating system is the most widley misunderstood system on a vehicle followed by the A/C. I laughed at him for saying that, but he may have been right. Personally Automatic Transmissions are harder for me, but not enough to keep me from boring out my own valve bodies.

 

Many people have a misconception that A/C provides cool air, as in the A/C in your car, refrigerator, home A/C etc. That fact of the matter is no A/C provides cool air it simple removes heat. You could look at an A/C system as simply another form of a heat exchanger.

I remember a few years ago having a conversation with a guy at work that had a problem with his A/C in his car. He told me it wasn’t blowing any cold air no more and he thought he knew the problem. He went on to tell me that since he had been running his A/C with the windows down that was the root cause of his problem…

 

That is 100% correct!!!
AC is indeed the lack of heat... much like white is not a color it is the lack of color.

Your home A/C and Heat unit uses the same fins, coils, and condensor, etc. to perform both functions (heat and cool). It just reverses thier operation.

Now we have confused everyone even more....I wasn't even going to go there yet....

Edit:
Later added
My conversation with the teacher may have been revesed A/C being the most commonly mis understood and Heat as the second....It's been a few years since school for me.

Please forgive me Mr. Stephens if you read this and I had it wrong.

 

LMAO...

 

One that I never can remeber is...
Is dark the absence of light or is light the absence of dark? Hmmm