Special parking heater project

Hi together,

as I'm well known for going strange and uncommon ways sometimes, I want to present you my
parking-heater project. Currently I'm still in planing it and I'm happy about comments and also,
if necessary, concerns about the plans, too.

The original setup for the parking heater is like that:


This heater doesn't only heat the car inside, it also brings up the engine to 80 degrees.
It has a power of about 5kW and is able to be driven with gasoline or diesel.
It has an realy to switch on the blower motor for heating up the cabin. But havin such a big cabin like the Bronco has, it's better to add an additional heater-core below the rear-bench, to supply the cabin equaly with warm air. So, that's my opinion.


I plan to connect the air outlets to the for me not useable openings for the 3-point belts of my 90th interior, by 3D-printing air-outlets that will fit in this holes.


I already have done a schematic for the water circuit:

OK...it's a bit more complex than the original. But this has a reason, as some will assume.

I have added two electrical coolant valves to control the circuit.

If the engine is off, the parking heater will supply the engine, the original heater core and also the seconday heater core.

If the engine is running, both valves will be switched. So, both cooling circuits will be sperated. With this strategy, I can use the parking heater also when the engine is running, without heating-up the normal coolant circuit of the engine. The reason for this is, also to supply the rear-bench with warm air for the children.

I still have to find out, which signal from the ECU I can use to know if the engine is running, but there will be one available for sure...

So as figuring out the upon, I have got another idea. As I will place the parking heater with all accesories below the rear bench, under the car, I also will add a fuel tank for the heater...so with a small modification, I may be able to use this fuel tank as an emergency tank for the engine...


What do you think? I will place a switch inside the cabin to activate this valve, if necessary. I also have thought about to get a secondary fuel gauge for this fuel tank and replace the amper-meter, that I can't use cause I have the 3G-130A alternator...

My only problem with this is, that I currently don't know where I can place the filler-hose for the secondary tank...the tank sould not so big...something between 8 to 10 gallons.

I'm very exited about your comments...

Wow!  That's quite a project.  

I don't have time to fully comprehend it right now as I'm headed off to church.  But I don't have several questions:

What is the overall goal?  Have a warm engine when you are ready to go?  Have a warm interior then?
 Or have more heating capacity for the rear of the Bronco?

Have you thought about the fact that the HVAC system's doors won't move to the proper position w/o the engine running?  They take vacuum and w/o vacuum the air defaults to the defrost position.

Have you considered a block heater?  With one or more of these you can have the engine quite warm when you are ready to go somewhere and heat from the HVAC system will come on quickly.

Also, have you considered a rear seat heater?  The E-Series vans had those as an option and you'd have a lot more heat in the cabin.

Rene' an oil pressure switch (later trucks used them instead of a functioning oil pressure gauge) it is a normally open switch that closes with oil pressure. That could provide the needed function to operate a relay to change the system into the engine running mode.

Nicely thought out system!

As Gary mentioned E-Series vans had a rear seat heater option. Chrysler built minivans had a rear heater and air conditioner option that resided in the left side of the van in behind the interior trim. It delivered heated air under the middle seat, and cooled air through vents on top of the trim at the bottom of the side windows. Our two Ford Flexes have a rear heat and AC system that can be controlled by the driver or passengers in the center seats. Heat is delivered left side under the seat, cooled air through adjustable vents in the headliner.

Hi Bill, thanks for the roses...

Yes, I have nearly the same for my CJ7.
A T-adaptor at the bore in the block. One end for the gauge and another for the switch. But firstbill check the ECU signals. I'm relative sure I'll find a signal that provides 12V or 5V only when the engine is running. Combined with a relay, I can use it.

But your option may be a very good alternative.

What do you think about my emergency-dual-tank valve?

And the more relevant question: is my coolant circuit usable without disturbing the stock circuit?

Hi Gary.

Thanks for the questions.

My primary goal is to have a warm cabin, when it's cold outside. The warm Engine will be a nice feature that the parking heater, I've already bought, last year, will provide.

The HVAC system was also a point that leads me to add an additional heater core.
Having it on defrost position will provide free windows when starting. The additional heater core will provide a warm cabin.

To use "only" a block heater won't provide a warm interior at startup, as they won't switch the fans and haven't a own coolant pump.

I don't know the E-Series rear seat heaters...but if this are only normal seat heaters, they won't help to get the cabin warm, before you'll enter it...

The only ECU circuit I can think of would be the fuel pump relay control if functions by grounding one side of the relay coil, the other side is powered with the key on. I don't know if the circuit inside the EEC would handle two relays, it might for a while, but long term is an unknown.

If the goal is to have a warm cabin before you start the truck then one or even two block heaters won't do that, even with a rear heater.  That's because a block heater won't get the coolant up to something like 180 degrees, nor will it circulate the coolant.

As for the E-Series rear seat heater, it isn't an electric seat heater but a heater core like the front one through which coolant is circulated.  As shown below.

Ok...so it's nearly, what my plan is. The difference is, that I'll able to get the parts that I plan here in Germany. Original parts are hard to get, as we haven't any junkyards here anymore and much less broncos, as well...