elec heat - anyone done it?

[911tracker85]

saw a post about the idea to install a small 12V elec heater in lieu of the exhaust heat exchanger some time ago. referenced some little heaters, but none installed.

did some searching and only found one where they used a gas heater. not sure I like the idea of that. did not read fully.

anyone every installed a small 12V elec heater just for defog and a little interior heat? it looks like if you want much heat, the amps it will draw could be a killer.

ironic a lot I found when searching are in Australia

found this little one, 300W @ 15amps.
New 300 Watt Electric Heater w Fan for Golf Cart RV camper Auto Car 12V | eBay

but hoping to find something more like this in a lower watt/amp.
2 YR WTY Fully Electric 600W 4 Outlet Universal Heater Blower Demister Unit 12V | eBay

my car won't be out when below freezing.

thanks and sorry if my searching missed what I am curious about.

[Mick_D]

I hope I can find something similar. Bit i wont be too upset if i don't.

[911tracker85]

I do not plan to give up easily. but not sure if 300w would do much. but maybe enough for defog the windshield.

not real sure the car will see much use in weather conditions that would require any HVAC.

found a lot of very small unit that sit on the dash to demist/defog the windshield. very small....

next question is upgrading alternator for more amps. I am pretty much stripping this car. removing AC, PW, PL, no radio, no rear window defog, etc. so the load on my alt / elec system will be a lot less than those with working AC and heavy duty stereo systems, and all the factory power stuff.

ironically I know about the car's elec systems pulling too much amps. low amp alternator is one of the limitations of the older 928s. turn everything on and you can see the alt gauge drop to a very low point.

[911tracker85]

PS. found this one. info say you can disconnect one or two of the element to drop the heat/load from 620W to 412W to 206W.

Safe 12V DC Heater 12 Volt 620W Hornet 45 Electric Automobile Truck Auto Car | eBay

and another 360W unit.
DC Thermal 12 Volt Cab Heater Brushless Direct Hook Up SA12 3000 | eBay

[WinRice]

Originally Posted by 911tracker85

found this little one, 300W @ 15amps.
New 300 Watt Electric Heater w Fan for Golf Cart RV camper Auto Car 12V | eBay

I think their math is a little off, 15A x 12V = 180 watts

The alternators up to 83 were 75A and 84-89 were 90A, pulling 30A from one of these is a pretty good current draw and the alternator probably will not live long.

I see aftermarket alternators with higher amp ratings, but who knows if they're accurate and how long they'll last at that load.

One wacky thought, if you're not running A/C, is to build a bracket and run a second small external alternator in place of the compressor, similar to a 935 flat fan setup. Then use that just for the heater, and it wouldn't effect the rest of the car if it craps out.

[infraredcalvin]

Not mine, but a buddy was considering this for his 74 Carrera....

http://forums.pelicanparts.com/porsche-911-technical-forum/630428-two-300-watt-hair-dryers.html

[Jonny H]

I have been here. I custom made 2 X 420W PTC heater/blowers that were fitted where the footwell blowers would normally go. A microcontroller based control board detected the battery voltage and shut the passenger side off if the voltage sagged.

I'm sorry to say that even with 840W of heat, drawing 70A from the battery, the heat delivered was not sufficient to warm the cabin if the temperature outside was less that 10 degrees C.

The 70A alternator just isn't powerful enough.

[Mick_D]

Well, poop.

Originally Posted by Jonny H

I have been here. I custom made 2 X 420W PTC heater/blowers that were fitted where the footwell blowers would normally go. A microcontroller based control board detected the battery voltage and shut the passenger side off if the voltage sagged.

I'm sorry to say that even with 840W of heat, drawing 70A from the battery, the heat delivered was not sufficient to warm the cabin if the temperature outside was less that 10 degrees C.

The 70A alternator just isn't powerful enough.

[930cabman]

Take it from a 45+ year air cooled wrench, use the heated air from the engine. By far the safest and most reliable. Sure it can be a pain in the a** to get it right, but worth it.

Gas, too dangerous. Electric, way tooo much power required

[908/930]

Probably around 3000w would work, would need another alternator.

[clutch-monkey]

Originally Posted by Jonny H

I have been here. I custom made 2 X 420W PTC heater/blowers that were fitted where the footwell blowers would normally go. A microcontroller based control board detected the battery voltage and shut the passenger side off if the voltage sagged.

I'm sorry to say that even with 840W of heat, drawing 70A from the battery, the heat delivered was not sufficient to warm the cabin if the temperature outside was less that 10 degrees C.

The 70A alternator just isn't powerful enough.

if my only concern was to demist the windscreen, do you think it would be sufficient? (outside temps would not be below 5-10 degrees).
i did see heated windscreens for sale though..

[boostfix]

Has anyone looked at how Tesla does it? Free engineering to copy

[Jonny H]

Originally Posted by boostfix

Has anyone looked at how Tesla does it? Free engineering to copy

Electric cars run at many hundreds of volts, hence they need much less current to run the heater. They don't have alternators.

I have an electric 914. Battery pack is 144V and will run a 2000W heater. Only 14A required.

I have a heated screen in my 911, works ok but is not as instant as you'd imagine. Check one out first on somebody else's car would be my advice.

[proffighter]

Just for comparison:

I have an Eberspächer gas heater. The heating performance is 2500 Watt, which is just enough to defrost the windscreen and get a little warm (not what you call confortable) in the cab, but only if it's not below zero degrees Celsius. Real heating needs more power. Remember, they are made to heat while car is not moving (camper etc...)

BTW, my car has no insulation, so performance may better in a stock car with carpets etc...

[911tracker85]

thanks for the replies.

still considering what I'll do. if I go elec heat, mainly for windshield defog. doubt the car will ever see the road when temps are near or below freezing.

actually I like the idea of stuffing little hair dryers in the vent hoses.

pic before pulling the last of the HVAC stuff.

[mrm930]

try looking at this ESPAR heating. Same as used in the singer cars

My next project is including this as my heat source - then I can use a great header system and not be concerned with the heat exchangers

[911tracker85]

then I can use a great header system and not be concerned with the heat exchangers

exactly.....

[gumba]

I went through this a bunch of years ago in my vw bus. The electric hair dryers, industrial blowers don't work, too much amp draw as mentioned above. I guess you could add a second battery for the blower. I went with a gas heater, it was great. No smell and toasted up the cab in a few minutes.
The ESPAR set up is gas. Porsche used gas heaters, you might look for one of those, may be an easier fit.

[totle]

I tried with 2 12v electric hair dryers, but ended up with a webasto in the smuggler box

[911tracker85]

hmmmm....

one of the things I also hoped to eliminate is all the HVAC housing/blowers/etc.

but from looking at the posts with the gas heaters, it looks like they feed into all that stuff.

so I may still try the little 12v hairdryers for defog. really not sure I'll ever need real heat.

totle: was your need for the webasto in norway? what about Miami?