Electric Heater Load, Is 200 watts too much ? Options

[jim_hoyland]

Picked up a ceramic heater at Pep Boys this am; it plugs into the cig lighter and uses 200 watts. Is this going to be a fuse buster ? Will I have to upgrade the fuse ? Any tips ?

[skline]

Make a plug for it that goes straight to the battery using a relay and fuse that. Safe and it works.

[lapuwali]

(IMG:style_emoticons/default/agree.gif)

Yes, 200W at 12V is 17 amps. Use at least 14 gauge wire connecting it to the battery, and a 20 amp fuse. Put the fuse close to the battery, not close to the heater. You've only got a 50 amp alternator on the car, so you're using up a substantial amount of available power to run that heater.

[jim_hoyland]

Thank's for the tips; possibly avoided some unneeded grief.

[davep]

This is when a 75 amp alternator makes sense. I'm not sure just what current the car needs to keep running, but it is substantial. You can be sure the engineers never intended you to draw that much power from the alternator for an accessory.

[lapuwali]

Running the car itself doesn't take all that much. Ignition and injection and the injection pump take about 15-20amps. Lights, radio, and heater blower motors can easily consume as much. There's probably 10 amps of spare capacity if you're driving along with the brights on, the radio blaring, the turn signal going, both blowers going, with a turn signal blinking. My 912 has only a 25amp generator on it, but it also has carbs and a mechanical fuel pump. Just turning on the brights and the brake lights at the same time will max it out, which is why they went to a 35amp unit later.

[davep]

Then there is the wipers and rear window defrost. Let us not forget that the battery generally needs to be recharged for a while after starting. The 914 got a 50 amp unit and the 411 got a 55 amp unit. The 411 had to run 2 gas heaters as well. The cost difference must have been negligible, so why did they have two different units.

With a lot of attention to detail these units can output 90 amps. For that I'd suggest a new harness. Almost all my harnesses are burnt to uselessness with just the 50 amp unit and in under 10 years.

[jim_hoyland]

Thank's for the lesson(s) on alternater; you may have just kept one 914 from going off-line, or worse.

I'll wrap-up the 200 watt ceramic heater and put her on the garage shelf.

[Dr Evil]

Why scrap the heater? You can get a more powerful alternator in the resources section of this site. If you get your alternator to put out enough juice then your only other concern is to make sure that any additional accessories are wired with apropriate gauge wire and fuses.

[airsix]

Why scrap the heater? You can get a more powerful alternator in the resources section of this site. If you get your alternator to put out enough juice then your only other concern is to make sure that any additional accessories are wired with apropriate gauge wire and fuses.

I agree. Go ahead and use it - just don't run it for extended periods. I've got one - they were on sale at Harbor Freight for $4 or something rediculous like that so I picked one up to try it. I have to admit that it puts out a fair amount of heat. I don't have heat in my 914 and have used that little heater in it a few times. I just didn't run it continually for extended periods and never had a problem.

-Ben M.

[jim_hoyland]

Were the HArbor Freight units 100 or 200 watts ?

[ClayPerrine]

When I was driving my 914 on a regular basis before I started the /6 coversion, I had 2 electric heaters that I mounted over the holes for the heated ducts under the dash. THey worked great. Instant heat, and no problems with oil smell. But when I ran them, the battery would go dead. The alternator could not keep up. I installed a high output alternator, and I could run one heater without killing the battery. If I ran both, I had to put the car on the battery charger when I got home every night if I wanted it to start the next day.

[jim_hoyland]

What is your high output alternator rated at ? Should I consider having an extra unit rebuilt or do I have to order a whole new unit ?

Are the higher output units readily available ?

Thanks,

Jim

[ClayPerrine]

When I had this done, I was still working on cars for a living. I had the shop that did all of our alternator and starter rebuild rewind the alt to make the additional output. It was tested to 85A.

I have no idea how much this would cost to by now.

[Maltese Falcon]

I ran the model called "Back Seat Heat" in my Vanagon 3.2/ 6 cyl for about 4 months.
It was installed per instructions, and ran with a 30 amp fuse right off the battery. The Bosch 911 alt kept up with the amp draw and the heat was nice. After about 4 months, the heater started blowing fuses, and melting the fuse holder. Not wanting to hurt the alt. or torch the van, I disconnected it. The unit was defective, and I couldn't reach the co. for service...they proll'y closed up.
Harbor freight = made in China / buyer beware ! (IMG:style_emoticons/default/ohmy.gif)

[davep]

High Amp Alternators