Car Pre-Heater (Remote Start Alternative)





Introduction: Car Pre-Heater (Remote Start Alternative)

About: There are some things you should just never, never, do...

Car Pre-Heater

What could be nicer on a cold winter morning than getting into a warm car!

But how?

Remote start is an option, but for most its an option that must be installed aftermarket and with your car idling you end up burning a lot of gasoline while sitting in your driveway. Not to mention needlessly polluting the environment.

An alternative solution is to put a small electric heater in your car, have it on a timer and turn it on to heat your car before you get in it. It can really get the car nice and warm, and its great at melting snow and ice off your vehicle.

Now I know that this is not warming up the engine, but with a warm interior, you can drive your car until the engine is warm with very little discomfort. Also, having the electric heater in the car helps melt ice on the windshield and other locations that may have accumulated on the vehicle before you go to use it.

Step 1: Supplies

To pre-heat your car you need:

Small Electric Heater

(The type that blows air. Do not use radiant or other types. The heater should be of very stable design and not easily knocked over. The heater should have mechanical switches, not electronic since it will be powered up without you there to set it.)

Outdoor Extension Cord (Suitably Rated*)

Outlet Timer (Suitably Rated*)

Extension Cord Connection Box (example)- Optional, needed if heater cord exits vehicle.


*A Suitable Electrical Rating is essential to make sure you are not overloading the device. Electric heaters draw lots of electric power and the cord and timer need to be rated for at least the electrical load of the heater or more.

Also to prevent energy loss and excess heating, long extension cords need to be the correct gauge (or size of wire). The larger the load and the longer your extension cord needs to be, the larger gauge it should be (For wire gauge the smaller the number the larger the wire size; i.e, a 12AWG (American Wire Gauge) is larger than a 14AWG cord). Here is some excellent information on selecting the correct extension cord.

Step 2: Put the Heater in the Car

Now this step can BURN YOUR CAR TO THE GROUND if done improperly! Please be careful.

CAUTION - This is an electrical project utilizing hazardous household (mains) voltage and current. You are also using an electric heater that can easily start fires. Making a mistake can result in property damage, personal harm or even death. You need to be familiar with electricity, heaters and their hazards. If you are not knowledgeable and comfortable with this project do not attempt it. You take full responsibility for the project you build/assemble. I may be taking risks that are acceptable to me, but may not be acceptable for you or your circumstances. Build/assemble at your own risk. If you do not understand or have questions consult a professional. Sorry for the disclaimer, but if you burn something down or kill yourself it's your own fault, not mine. :-)

Electric Space (Air) Heater instructions tell the user to keep all flammable materials at least 3 feet from the front, top and sides of the heater. This is important because if you don't keep flammable materials away they can catch fire! Virtually everything in your vehicle interior is flammable so technically you need at least three feet from the heater to any portion of the interior of your vehicle.

Placement of the heater in the vehicle is critical and must be verified as correct or you can DESTROY YOUR VEHICLE!

I NEVER use the heater on its highest setting. Always use the LOWEST SETTING if it will do the job. If you can place the heater in a back open area (like the flat cargo area in the back of a minivan) where you have 3 feet of clear area on the front and sides this is ideal. However, most of us will need to put the heater in a more confined location.

In order to set up your heater in your car without the necessary three feet of space around it you should do the following: (You have to decide if this is something you want to do since it is not following the heater manufacturers instructions and introducing risk - so be smart. Your situation is unique and may not be suitable for using a heater).

Run your heater in the house and get a feel for how the air exits the heater. Note how the hot air flows. Often because of fan rotation and grill design more air will exit one side of the heater than another, or the air will exit at an angle you would not expect. Back out in the vehicle, based on your finding the path of the exiting air, place the heater so the airflow will be directed away from nearby surfaces. Make sure the heater stable on a level even surface so it won't be likely to tip over should the vehicle be jostled. With the heater on the lowest setting run the heater for a couple of minutes and then open the car and feel the adjacent surfaces, including any overhanging projections (dash, etc.). Make sure they are only reasonably warm and not hot to the touch.

Repeat the above 'test' of running the heater and checking for overly hot surfaces for 5, 10, 30, minutes etc to make sure that the heater is not overheating any surfaces and causing a fire hazard. If a surface gets too hot you can try repositioning or relocating the heater. If a surface still gets too hot you will not be able to use this Instructable. When it doubt, don't do it -- better to be cold and have a car than burn it to the ground. :-)

Make a mental note of the heater's location (or even mark on the floor mats the location) since you will most likely be leaving the heater in the car and will need to reposition it each time you use it.

Step 3: Run Extension Cord From Vehicle to Outlet

Run the extension cord from the vehicle to the electrical outlet. Finding a suitable electrical outlet may be the most difficult part of this instructable. The electrical outlet needs to be a GFCI (Ground Fault Circuit Interrupter) type that is protected from the elements so that when it is in use the contacts are not subject to rain or other moisture. The timer also needs to be protected from the elements unless it is suitable for outdoor use and exposure to rain, etc.

The extension cord is going to exit the vehicle through the door. It is important to make sure the vehicle door does not pinch or damage the extension cord. Clearance between the vehicle and body vary from model to model and vehicle door gaskets vary and yours may not be thick or resilient enough to prevent damage to the cord. If the extension cord is too thick to pass through the door then you can try the heater cord as it is usually the flat style and thinner. If both cords still get pinched, damaged or look like they might be, then I'm sorry but this Instructable will probably not work for you.

Of course, if the heater cord is exiting through the door and you are making the connection between the heater and extension cord outside of the vehicle you need to use some type of weatherproof cover to keep things dry and safe.

Step 4: Set Your Timer and Plug It In!

Set your timer per the manufacturers instructions with the correct time of day and when you want the heater to turn on. Make sure the heater is turned on to the lowest heat setting and plugged into the un-powered extension cord. You can experiment to see the amount of time you want the heater to run to get the car nice and toasty warm.

It is also wise to set an off time to turn the heater off just prior to using the car so that the extension cord is de-energized and not a risk of shock when you unplug the heater - particularly if it has been raining or snowing.

When you enter your vehicle you can unplug your heater, make sure its cord is inside the vehicle, and make sure the extension cord is outside of the vehicle. The unplugged extension cord should be protected from the elements and out of the way of the vehicle (don't drive over the cord) and not in the way should other vehicles pull into the same location.

You're now ready to drive off in a warm vehicle!




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    24 Discussions


    2 years ago

    Sure it may be warmer, but do you not realize how bad it is to not let your car warm up in the winter before driving. That is so bad for your engine and can cause you much bigger bro lens than being cold for five minutes

    4 replies

    The need to warm up a car's engine went by the wayside with the change from carbureted engines to fuel-injected ones. In the past, the engine needed to be warmed up to optimal temperature so the air/fuel mixture would be adjusted right or else the car would bog or stall out when you tried to drive it away. Now, the car's ECU automatically adjusts the air/fuel mix, so you can start the car and drive it almost immediately. In fact, it is harmful to the engine to let it idle for too long because gas will clean the oil off of cylinder bores and cause excess wear, as well as mixing with the oil itself. That, plus it is actually faster to charge your car's heater core by driving it than by just letting it idle.

    My concern with using any kind of space heater inside an unattended car is that you're putting a heating element that gets rather hot in the more or less immediate vicinity of materials that can either melt or catch fire. Not that I know if the heating element can reach a temperature hot enough to melt plastic or ignite the fabric of the seats, but it's a possibility. Also, the presence of an extension cord raises the specter of a possible electrical ignition.

    My advice: Suck it up and dress warmly for the walk to the car and the five or so minutes it takes for the heater core to charge, or move south.

    Just do what my GF used to do, turn on the car and rev the engine up to 4000 RPM... You kill 2 birds with one stone, and one of those birds being killed is your car!

    Well, this could also be used to defrost the windows which can take much longer than it is to warm up the engine.

    I agree. There are definitely benefits to your engine to let it warm up before driving, especially in extreme cold. I used to use the heater in a less extreme climate. Even so, perhaps it is a good idea to split the difference - get into a warm car from the electric heater and then start the engine and let it warm up for a couple of minutes before driving off. Obviously this instructable is not the 'be all' 'end all' for everyone.

    Thanks for the comment!

    That may be OK if the garage is heated. Everybody's situation is different.

    I was surprised after moving to New England by the number of houses that did not have any garage. Especially considering the winter weather. My house does not have a garage.

    Hey, if you want a warm car on a snowy morning you can have a remote starter installed, or if you can not afford that, a person can try my in-car heater (while being appropriately safety conscience.).


    2 years ago

    Ha! I was doing this in 1988 in North Dakota, Block heater & space heater in my Mazda B1600 PU Truck, the only vehicle in the lot with all the snow melted off the windshield every storm :)

    In reality, this is a dangerous idea and could be very bad for many people. I would suggest an engine block heater and/or remote start over this.

    Also, why would you use a heater that blows hot air and not a oil filled radiator?

    I would think the safest way would be to get a remote start. Set the heater to high the night before so when you turn on the car it will be nice and toasty + the engine will be to operating tempture.

    2 replies

    > why would you use a heater that blows hot air?

    Because the purpose of this article is to get hot air into the car, so a device which is designed to do exactly is the obvious choice :)

    An engine block heater will not heat up the car's interior so it wouldn't work at all for the purposes of this article (see first sentence on this page).

    Oil filled radiators are very large and heavy for something you need to put in and take out of a car every day. They wouldn't physically fit in the footwell of most cars and the castors would likely damage the car seats due to the weight. They're also very inefficient to use for short periods and take ages to get warm (as you have to warm up all the oil first and then wait for that to radiate and convect heat out) , so they are the exact opposite of what you need to get a quick burst of hot air into a car.

    I don't agree that remote are safe as they leave the engine running and also allow anyone to steal your car more easily. Due to safety concerns, they are illegal in most countries (including here in the UK). They also cannot be used in garages (due to fumes).

    I like your suggestion of the oil filled heater, but they are so large and they can still radiate heat to adjacent surfaces. A remote start and running your car for a few minutes to get the engine warm is a great idea. However, adding remote start is not an option many of us would consider on a tight budget. Thanks for the comment.

    many years ago (maybe 1989) my dad made a set-up like this for my NEW car. it worked well. then one day, i opened my car to find the heated melted, emitted toxic black smoke that collected on every single thing inside the car...seats, windows, even inside the dash where the odometer was. i cried. it was covered by insurance but it took 3 months to get the necessary parts due to the car being so popular at the time (1988 ford escort) nowadays, heaters have cut-offs to protect from overheating & tip-over switches.

    1 reply

    Sorry to hear about your misfortune. Yep, a heater can make a big mess of things if stuff goes wrong.

    Even today not all heaters have tip-over switches, they just have to use some means to pass a UL Safety test tipped over. The test does not necessarily require a tip-over switch - However I think choosing a heater with a tip-over switch is a good idea.

    Thanks for sharing!

    Pretty risky there!
    1. Extension cord female end should run inside car not exposed to outside element
    2. I'd plug that extension cord male end to a GFCI outlet
    3. If using timer, better use one with the three prongs to ensure proper ground especially in wet outdoor environment and plug timer to GFCI outlet then extension cord.
    4. Ceramic heater way too hot. Hang/suspend a hair dryer by its cord to the rear view mirror so it blows wherever and not directly to vehicle plastics or upholstery.

    1 reply

    Thanks for the comments.

    I think we are on the same page. Per your items:

    1. Preferred method is to have the extension cord connection inside the car. As stated the heater cord only goes outside if needed to prevent damage to the extension cord. If the connection is outside you have to use a 'cord connection box'.

    2. Use of a GFCI outlet is stated in the instructable.

    3. I agree with the grounded extension cord/timer and this is what I show. However, I doubt anyone will find a two conductor extension cord over 15 feet long. Also virtually all residential heaters are only two prong so what does it add?

    4. States only use a heater that blows air - no other type.

    There are lots of fires with people using hair dryers as a heat source for other than drying hair. They are not made to operate long periods of time and hanging from the cord is not their normal orientation. I'd be careful with that suggestion.

    Thanks again.

    Although this is clever, it really doesn't heat the engine. Thanks for the idea though :)

    2 replies

    Thanks for the comment.

    But what's the point of starting your car before getting into it? To heat the cabin! [Unless you live in a really cold area where you need an engine block heater. :-(]

    As I mention, with the cabin warm you can easily wait for the engine to warm up as you drive.

    not 3 hours ago... the timing is off on this site. But, it's 3:57 and I posted this just 2 minutes ago..... Amy

    They also make a 12 volt heater for VW's that works well, I used one in my old Mustang when I was in Colorado!

    so doing this have tge most perfect fan or 1300 or 1500 watt switch i bought at tard sake...tge thermostat design was so stupid it was plastic against hit metal...i tiok it out and by oassed it so it has switch to fan,1300 or 1500 watt its very stable but i will make a car seat basr for the baxk seat in middle of wood necause since i bypassed the tgermostar the safety knovk over switch as well is bypassed(made out of part of thermostat)(dumbesst thermostat design ive eve seen i mean comin lowes olastic and hot copper does not mix well lol)