Rapid-Heat Supplemental Heater
 

Just purchased my First 2012 F250 Crew Diesel and it came with just about everything you could ask for to include a Rapid-Heat Supplemental Heater. So I've had it about a week and every morning I let the car run (remote start) for about 10 min before getting in. I make sure I set the heat to 80, make sure the system is set to auto before turning off the truck the day before, but every time I get in the car, its still freezing cold inside (this morning the temp was 26 degrees out). I have read many postings about the supplemental heater, but I have no idea how this is suppose to work. The truck will heat up nicely once I'm about 10 min down the road, and even quicker if I'm driving and take it off AUTO and control everything myself. So if possible can you guys give me some feedback on the questions below. Maybe come up with a few tests that I can perform or let me know how your system works?

1. Does the supplemental heater utilize the air vents in the car, or is it a separate system that heats the car?
2. Can someone tell me where the heater is located so that I can verify that it is actually installed.
3. Is there anyway other than taking it to a dealership to verify that it is working properly.
4. Also is it normal than heat doesn't come out of the rear center console vents while driving?

The Rapid Heat Sup-Heater is electric elements in the duct system. I have it and it works well, but I never remote start my truck, althought it has remote start. When the dealer was going over things with me, I did notice many electronics did not activate until the key was inserted and turned on after remote start.

Someone else may come along with more experience, I just love the truck.......

You say it's in auto so that should be working.
I don't have it but my understanding is it helps heat the cab more quickly once EGT's begin to heat up the engine.
I don't know that it is designed to make the cab hot from a cold start and idle.

For the back vents, I'm fairly certain heat flows from the ducts under each front seat instead of the console vents.

Until someone who does have it comments, here are some details for this system for now.

Welcome to FTE!!! Congratulations on the new truck.

The Rapid Heat supplemental heater is a electronic heater element installed in your ductwork as mentioned above. You can't see it unless you take your dash apart. But if it is on your sticker listing all your options, You got it.

There is no operator controls to turn it on or off. It is totally automatic. When the tempeture is below a certain point and the engine coolant is below a certain temp, Then the suplimental heater elements kicks on. It is only a 1500 Watt heating element. Think of it as a Hair Dryer. So it's not going to totally warm up a Crew cab that has overnight cold soak, where every piece of plastic is 20°. But it will help get your windshield defrosted faster. During the winter months, when I remote start the truck, I can come outside after 10 minutes and find all the frost on my windshield has pretty much been melted.

I don't know what Temps you are seeing in VA this fall. But it may not be getting below the trigger point to even turn it on.

Painted.....actually I don't think it's auto. On my xlt with manual heat the manual tells me to turn the heat to full hot. That acutates the supplemental heater. Then I turn back the heat to the 3 oclock position and you can hear a difference in the heater and it's truck heat at that point.

It appears from the details below, that it's automatic on the dual climate automatice systems, but you need to turn you controls above the 80% level on the manual systems to activate it.




An electric heater is available as optional equipment on diesel vehicles. The electronic heater assembly contains the Auxiliary Heater Control Module (AHCM) and element, and is located in the HVAC immediately downstream of the heater core.

Power is supplied to the AHCM element through a fused cable connected directly to the positive battery terminal with an in-line connection at the dash panel heater tube opening. Ground is supplied to the electric heater element through a ground cable connected directly to the negative battery terminal with an in-line connection at the dash panel heater tube opening. The AHCM is activated by a Medium Speed Controller Area Network (MS-CAN) message from the HVAC module — EMTC or HVAC module — DATC . The MS-CAN message is converted to a HS-CAN message by the Instrument Cluster (IC) module and is then detected by the AHCM .

The electric heater will be activated if all of the following conditions are met:

The ignition switch is in the RUN/START position
The engine is operating at greater than 500 rpm
Any ON mode is selected on the HVAC module — EMTC or HVAC module — DATC
The temperature set point is greater than 80% of the highest setting ( EMTC only, DATC uses software algorithm based on interior temp and set point)
The engine coolant temperature is less than 85°C (185°F)
No alternator faults have been recorded and alternator is not at full capacity
The AHCM will be deactivated if any of the following conditions are met:

The ignition switch is in the OFF or ACC position
The engine coolant temperature is greater than 85°C (185°F)
An alternator fault has been detected or the alternator is fully loaded due to external electrical loads
The engine is operating at less than 500 rpm
The auxiliary heat request is NO from the HVAC module — EMTC or HVAC module — DATC

If the ambient temperature outside is above freezing, 32F or 0C, the Rapid Heat is inoperable. If cold enough, it works as described above. It thaws the windshield and knocks the chill down a bit...it truly is just a 1500 watt hair dryer installed in the heater plenum...

Regards

I know on my Lariat it's been working every morning with 40-60 F degree temps outside. I can feel heat within literally one minute. Sure is nice.

I did some testing shortly after I got my truck to see how fast I got heat with the supplemental heater and posted the results in the spreadsheet in the link in my sig. You could do a similar test to see if you get the same results that would verify that you have the supplemental heater.

Based on how the system is supposed to work during remote start I would suspect you could check the air temp of the vents after x minutes of remote start to see if the system is blowing heat similar to what my truck was.

While far from scientific, my 2016 F-350 is blowing warm air within 2 minutes of driving. In fact I don't know why they don't offer it on all their vehicles gas or diesel.

Mine comes on when in the 40's.

You guys did some digging to resurrect this one from 2012....

You lucky person... Mine doesn't seem to work until it's in the low 20s in the morning. It's odd that if it is 30F out that it takes SOOOOO much longer for the heater to blow out warm air than if it is 20f out.

And yes, good work picking up a thread from the past.

Why it isn't in a gasser - My gas vehicles still start to blow HOT air quicker than my diesel truck... So unless you were in extreme cold often enough - like Fairbanks -60F cold, it probably wouldn't make a lot of monetary sense for the manufacturer or the purchaser.

I don't believe the outside temp has any effect on whether the supplemental heater operates or not...it only checks to see if the coolant temp is below a certain point, and whether near maximum heat is being called for. On the manual systems (which are actually all electric underneath), functionality is simple - cold start any truck, even on a summer night where it got down to 70F, and turn the heater knob all the way up...the supplemental heater will turn on. On a truck with full auto climate controls, the computer interferes a bit because now the system knows the cabin air temperature. If the interior of your truck is 70F and you set the heat to HI, some unexplained algorithm is used to determine if the heater comes on or not. In either auto or manual climate, however, you will hear a relay click when the heater turns on.

The electric supplemental heater basically looks like a mini heater core, and it is downstream of the actual heater core in the HVAC unit in the dash. This magnifies it's usefulness, because its much easier to heat warmer air. So if the coolant temp flowing through the core is 50F, that is definitely warming the air a tiny bit prior to the electric elements heating it a bit more.

Low blower settings work best; fast fan speed quickly overwhelms.

The reason it is even there is because the diesel engine takes much longer than the gas engine to warm up and provide significant heat. Remote starting your diesel and trying to defrost ice from the windshield would probably be futile without the heater.