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MG MGB Technical - anyone tried an electric heater?

I've been contemplating the use of an electric heater instead of revamping the old heater box. I'm sure that a full overhaul will increase it's output and the heater valve is a prime suspect but the thought of instant heat is very appealing. Walmart is selling two different model auto heater's that plug into your cigarette lighter. My thought is that I could mount two of these in eitheir footwell, not exactly sure where yet and obviously the driver's side would need to be out of the way of the pedals. I would plan to chop off the cigarette lighter plug and hardwire then into a two way switch. One click would power on the driver's side the second would power on the passenger side one. I haven't quite figured out the demister would work but as it is now they don't work anyway and I've gone 2 years that way so I guess that's not to important. My only real concern is the wiring and the amount of voltage they might draw. I currently have a recently rebuilt Lucas alternator which seems to provide plenty of power but I'm worried about the draw if both heaters, headlights, and radio are going. Perhaps a new fuse box with relays....? Any ideas? The heaters are selling for $12 a piece for the smaller model and there are 2 sizes. They also come equipped with a fan but no thermostat. You've got off, on, and on with fan for selections. Maybe someone has thought of this before. The 6 mile drive to work leaves me with heat for probably the last 1 1/2 miles. Seems like an easy upgrade.
David Favero

What is the heat output of the factory heater, I wonder (enough to burn my feet in mine)? What is the heat output/rated current of this heater? The most current you could draw through most MGB wiring is 17 amps which gives about 200 watts, which could be enough. But that leaves nothing for anything else on the circuit (i.e. sound the horns and you blow the fuse) and you can't draw more than 5 or 6 amps through a cigar lighter plug - it just gets too hot. Why don't you just fix the heater and demister? Seems even easier.
Paul Hunt

"12 Volt Ceramic auto heater/fan

Plugs into your cigarette lighter

Plugs directly into your vehicles cigarette lighter socket or other 12-volt power source as a strong auxiliary heat source and windshield defroster. Has a safe, effective PTC (Postivie Temperature Coefficient) thermistor to adjust power consumption as the unit heats up. The heater has two power levels of 150 and 250 watts. Switchable between fan (only) and heater. Includes 5 foot power cord, mounting stand/bracket with screws or self-adhesive velcro. CE Certified. Warning: do not use heater or fan without engine running. Car socket fuse must be 30 amps or above."

Ouch!
Paul Hunt

If your heaters really do succeed in heating to any extent, I would suggest that you consider hard wiring them back to the battery via a relay. You could accomplish this in the same manner as a horn or lighting relay installation. It will allow the current Paul mentions much better access to the heating element than the lousy bit of undersized wiring given to most cigar lighter sockets.

I have tried two different types of electric car space heaters as you describe and both were quite disappointing. Not only did they have a limited heating capacity, but as the air temp drops their effecacy goes down considerably. I hope yours prove me wrong. I just think it is rather sad that with the electrical heating technology we have available today, that no one seems to make good use of it. I have suggested to auto designers I have met that an electrical pre heater system in at least the heater ducts (on until water temp can take over) might be worthwhile. I have yet to see them in use. Someone like Paul or Rick Astley could probably give us some reasons why they aren't.

In the meantime, you might want to consider those hot water aux. heaters shown in the JC Whitless catalog. Some hot rodders use them to good effect. FWIW.
Bob Muenchausen

BTW, I meant using electric pre heaters in the DEFROSTER Ducts, not heater ducts.
Bob Muenchausen

David,

Your electric heater scheme seems more trouble than it's worth and potentially fraught with problems.

An MGB heater in decent condition will give you pretty good heat. I don't know why you suspect the valve, but replacing it is simple and inexpensive. If it's a cable issue, you might just as well set the valve to full on for the winter if you don't feel like troubleshooting right now.

A good flush and a winter thermostat might be a big help.

The previous owner of one of my B's years ago did something interesting. He had placed an MGB heater radiator under each seat. I forget now exactly how the hoses ran, but it would be easy enough to do. I wouldn't recommend that route but it was inventive.

Steve Lipofsky

Just an idea, but why not fix one electric heater up hardwired back to the battery with a relay and stuff, but remove the existing heater core and put the electric one in the the heater box. That wouldn't be too much trouble, would it?
David Ryzuk

Electric heaters are very nearly 100% efficient. The problem is the voltage*current needed to produce the watts. Just consider a typical car engine on a very cold day. Relatively inefficient at converting fuel to forward motion, the remainder of the energy is producing heat, most of which is being dissipated by the heater. Try replacing *that* off 12v, then just consider how much harder the engine is having to work to drive the alt, then consider all that extra coolant heat being pumped into the atmosphere ...
Paul Hunt

My heater wasn't doing all that much and I live in the mountains where it gets cold so I simply replaced my 165 tstat with a 190 one and what a difference it makes!I actually have to turn the fan to low.Your fix could just be that simple.
Pat
patrick bailey

I had thought about trying to place the electric heater where the heater core is but I wanted to see if it would at first work at all. As I have said, I was just testing the waters to see if this had been doen before. I do have a 190 degree thermostat in and it does in fact warm faster than my 160 and 180 but you can always improve on a situation. So if I'm understanding Bob and Paul correctly, one would need to hardwire it to the battery with a relay in-line to give enough power and not overheat the wire. I was curious about Bob's comments that the efficiency decreased as the temperature drops. Is this because the engine is working harder in colder temeratures and the alternator isn't suppliying sufficient power or there's just so many air leaks in the cabin that the heaters' can't keep up? We have been somehow spared with a snowless winter this year and I've seen many a classic car on the roads into December, I just can't get over driving in below freezing temps without having some sort of auxillary heat. When you walk into the driveway in the morning with frost on the ground and glance at the B and the truck it's a hard decision to make but the older I get the easier it is to choose the truck. I guess it's a bit too early to make the leap...
David Favero

David,

It is actually quite easy to make good heat from a B's regular heater. A good backflush of the heater core coupled with the heater valve modification on Bob M's web site should enable you to have all the heat you need. The electrical system is fairly close to capacity already, without adding the demand of an electric heater (big amperage draw) to it.
Paul Konkle

Bob said "effecacy" (sic) which is effectiveness more than efficiency, and any heater with a fixed output will be less effective (i.e. it won't be able to) at maintaining a given temperature when the heat loss increases i.e. as the outside temperature drops. As the temperatures inside the cabin drop (due more to poor insulation than air leaks) an electric heater will put out *more* heat in terms of BTUs/hr because there will be a greater difference between the air temp and the electric element temp, and the colder air will cool the elements more which will reduce their resistance which will increase the current etc. etc.

You wouldn't need to wire it back to the battery, just to the stud on the solenoid, with a relay positioned to give the shortest cable run. The air comes out of my heater at about 150F (ambient of 40F) which I find more than enough, but then I haven't had a 'modern' car for seven years. I never have the fan blowing into the interior, and unless it is exceptionally cold (for the UK) usually have to turn the heat control down to 'warm minus'. On defrost the fan clears the screen in seconds where it is just mist from occupants breath. Cold rain is a different kettle of fish, but the demister in conjunction with an open quarter-light clears a fully steamed-up (and keep your smutty comments to yourselves) car in a few minutes.
Paul Hunt

Have you considered using an engine block heater? You plug in into household current and it keeps the coolant in the car warm. It might be enough to "jump start" the heater on a cold morning and would seem much simpler than installing electric heaters. JMHO
Bud Goetzinger

They probably aren't available any more, but my first car, a 1950 Chevy, had an aftermarket heater (heaters were not standard equipment back then) that burned gasoline. It was a Southwind and used a glow plug to ignite the gas in a combustion chamber. Talk about immediate heat!
John Hubbard

Oh, I forgot, there was a gasoline burning Stewart-Warner unit used in Corvairs and a couple of different brands that were regularly installed in VW buses.
John Hubbard

Actually, wiring any item back to the battery cable solenoid stud is what I tend to mean for all relay wiring as that is essentially the same thing as the battery post, just a different location. The current carrying capacity of the battery to soleniod cable is more than sufficient to carry all the loads in the car, even with high power headlamps, electric heaters, etc. The only exception I have to this is when wiring a relay in for the rear window defogger on the GTs. Here it is simply a matter of logistics, the battery is right there directly under the defogger, no sense running back up to the solenoid when a short run through a small waterproofed hole in the tire well next to the battery will do the trick!

All that running an alternative circuit for an electrical item accoplishes, is not overloading the OE circuits. There is certainly some reserve designed into the OE circuits, but not always enough for accessories like these. As I have said before, as I have moved a few items out of the OE path and to their own, I have watched the performance of the remaining items go up slightly with each removal. From an empirical standpoint, this at least seems like a positive side effect.

What our GTs could really stand is a more effective air flow pattern thru the cabin. As Paul says opening the rear quarterlights is usually adequete, but not always, especially in rainy conditions. A constant flow-thru pattern as in most modern cars would probably enhance things at least a little.
Bob Muenchausen

I thought I'd get my two cents in here. Totally drop the notion of an electric heater. Lets be -quite- real about what type of car we are talking about, and Lucas, Prince of Darkness, wiring should -never- be considered for a high amp job (unless you've totally cleaned up the system).

The backflush notion that people have mentioned is really your best bet. There is another somewhat touchy idea that involves the use of some acid to clean things, but I won't start that right now.

There is an artical (you appear to be familiar with ) about fixing the valve off the engine. Its worth doing. OR if you're inventive, you can take a derelict valve, snap off the top part and attach a small piece of pipe and hook a hose directly to it. I recommend that you hook an inline valve so you can turn off the new source of heat.

Another way to increase the heating in the car is the old trick of covering the air intake duct in front of the windshield. Then open the "vent" in that impossible place behind the console. That makes it so your "reheating" your air.


Heres a goodie! Take out the fan motor (3 "bolts", 2 wires..) Now, measure the distance from the front of the housing to the rear of it (And suck out any crap thats built up inside the housing too!!!) Now, set the distance of the cage of the fan as close to the back wall of the heater without having it rub. This will increase overall air pressure, (thus air flow). If there is a huge gap, you will loose pressure.

Hope this helps.
Gord Bestwick

Forget the electric heat idea. You would need at least 1200-1500 watts to even hope of heating up the car and there is no way an MGB is going to handle that kind of system. The VW groups have struggled with this idea for years without success. I too recommend the backflush of the system. This morning it was 12 degrees here in mid-Missouri and my '72B was putting out plenty of heat. Cheaper to fix what you have then to try and jury rig something else.

Kurt V
Kurt V

I passed up a NOS gasoline powered heater for next to nothing at a recent swap meet because I'd already depleted my cash, but that strikes me as the instant heat solution. Block heaters are good too, although wasteful of electricity. I like the recirculate idea, never thought of that. Now the magnetic vent cover makes a lot more sense. The B heater core seems capable of putting out plenty of BTUs, but the fan, at least CB, is anemic. If the wires get reversed it will blow next to nothing as well. Plenty of newer cars have similarly sized blower motor& squirrel cage assemblies. Finding one with correct rotation should not be hard, and swapping it in should give much better airflow as the newer stuff seems to be more efficient. Shouldn't be any problem to go a bit larger as well. I went a bit overboard with mine and grafted in a much larger fan assembly complete with the snail, from a known high capacity system. May not test it this winter, but I doubt I'll ever need the high speed setting.
Jim Blackwood

This thread was discussed between 22/12/2001 and 26/12/2001

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