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MG Midget and Sprite Technical - Heater motor dismantle

ok, so I'm a woosie, but this year I would thought I would try and get my heater motor to work. I hot wired the heater to my battery and then my hands started burning, smoke rose from the wires, ouch! time to investigate. I managed to extricate the motor and fan without removing the heater box (just), undid the two body bolts, but then what to do, thought the unit would be simply bolted together to explore further. I'm assuming I need to drill out the three rivets ? (see picture) if that releases the inards what do I do then, is it possible to replace the motor bushes (a possible cause?)if so from where? and tidy up, will I need to remove the fan, if so how,(a devilish looking little clip holds it on I've not seen before), or do I need to start hunting for a second hand unit that might work?
any help, insight much appreciated, thanks in advance, Dave. 74 RWA 1275 Mk 3



DW Warren

It just pulls apart. The leads can be unplugged to remove the board holding the brushes. No need to drill any rivets.
Trevor Jessie

Looks like the same motor, some information here at the bottom of the page

http://www.scimitarweb.co.uk/~donkennedy/Heater/Heater.htm
David Billington

Dave,
In your photo one of the nuts is loose. So maybe the head of the bolt is fouling the impeller at the other end? Does the impeller fan turn freely? If not, then it would get hot pretty quickly. But the heat wouldn't last long and wouldn't be much good for warming you in the winter months.Even if it gets so hot that the car bursts into flames, it isn't recommended as the nice heat generated dies down after an hour or so and just leaves a mess at the side of the road.
Guy W

I have one apart on my workbench at the moment. Its failure was simply worn out brushes.
Trevor Jessie

Wow, I wasn't expecting someone from Kentucky to solve my problem in Warwickshire in under an hour, thank you Trevor! Yes you were right, the unit pulls apart after a little persuasion, David, thank you for going to all the trouble to find the article on how to fix it, Guy, for giving me good advice! the thought of my midget bursting into flames, hells teeth!! anyway as attached a picture of my inards so to speak, fingers crossed it just needs a little TLC as the brushes seem ok, here's looking forward to a slightly warmer winter! thanks chaps much appreciated, Dave.


DW Warren

If the brushes are good and the motor was not locked, then you may have a short in the armature or windings.

If that is the case, you may want to look for a cheap and functioning second hand unit.
Trevor Jessie

Dave,

I that one works then while you're in there it'll be worthwhile lubricating the bearings. I think they're Oilite bearings so a soak overnight then let the excess drain off should do it.
David Billington

you done well on getting just the motor out I don't think I could even if I took the battery out

bit of an aside - I only usually need to use the heater blower to clear the windscreen in winter, the heat is from having the heating/cooling system all clean and in good condition including the matrix and its seals along with cleaning, scraping and flushing the engine block and cleaning and flushing the radiator
Nigel Atkins

the solder where the brush leads connect to the brass terminals looks blackened

also the commutator looks discolored from some severe arcing

try some emery cloth on the commutator to see if it cleans up, then carefully make sure no residue is left in the narrow gaps between the sections of the commutator. Also check the condition of the brush ends, as they may have been damaged by the arcing.

definitely confirm the conductivity and the resistance of each of the windings, because I am with Trevor on this one: possibly a short in one of them caused all of this


Norm




Norm Kerr

Emery cloth or paper shouldn't be used to clean electrical parts because it is conductive and may leave traces behind that could cause problems.
David Billington

top replies from our boys across the pond, thanks Norm and Trevor :-) , made me even more determined to get it to work after your advice on screen heating Nigel, thanks, so I have to be honest David, I was going to use emery cloth to clean the commutator, as Norm said it is heavily blackened, not too sure how else or what with I would clean it, I'm not a specialist on "Electrickery"
regards and thanks again,
Dave.
DW Warren

I found this on ohioelectricmotors.com

The commutator should have a smooth, polished, brown appearance. There should be no grooves, scratches or scores. If there is any blackened, rough areas on the commutator, it’s probably caused by brush sparking. If a commutator has a brassy appearance, there’s excessive wear that could be caused by the wrong type of brush or the wrong spring tension. Check the manufacturer’s technical documentation to verify the correct brushes are installed. Carbon dust and debris from the brushes can cause sparking and damage the commutator. If the commutator is rough and the bars are uneven, it will need to be turned on a lathe to restore its roundness. To clean the commutator, use a commutator cleaning brush (fiberglass) and some electric motor cleaner. Never use emery paper because it has metal particles in it that if rubbed off could cause electrical shorts. Remove the brush springs, slide the brush across the commutator hood and spray. When done, blow out the motor so it is dry and clean.

Published by Ohio Electric Motors: http://www.ohioelectricmotors.com/dc-motor-maintenance-guide-610#ixzz2kEHnnta4
Dave O'Neill2

Thanks Dave, point taken (and dusty mind reminded, to use a lathe to clean commutator!).



Norm

Norm Kerr

I cleaned mine with electrical contact cleaner and an old tooth brush. One of mine had a damaged armature. I tried evening it out on the lathe, but there was not enough material left. So, I tossed in in the scrap bin.

I now have 0 spare Smiths heater motors.
Trevor Jessie

looks like I'll be paying a visit to Halfords, this looks like the stuff to buy... www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_195717_langId_-1_categoryId_255223

Dave.
DW Warren

Dave,
I don't know about electrickery especially on cars but that silicone spray I'd use more as a rubber lubricant, silicone spray can get everywhere and make things very slippery

I'd keep that can in stock for other uses and instead use an electrical contact cleaner (dissipates to air) such as - http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_195717_langId_-1_categoryId_255223

IIRC on CB points you use glass paper instead of emery or sand paper

leaving my post yesterday reminded me that I couldn't remember the last time I'd used my heater blower or tested it was working (as I do with electrics I don't use a lot, windscreen washer and horns) so today I tested it and tried a few experiments with my wife doing the heat tests

as the good book has it above about 25 mph it's a waste to turn the blower on (not sure about this for the windscreen during winter as we had the top down today) in fact as we were going above 25 mph with the blower on the heat was less (yes I have checked before that the fan blows the right way)

I'm not sure of the results of the optimum opening of the air intake flap as my wife was more interested in putting her glove back on and not taking it off again

as I put before the heat comes from the heating/cooling system all being clean and in good condition including the matrix and its seals along with cleaning, scraping and flushing the engine block and cleaning and flushing the radiator

I told my wife that some Spridget owners complain of the heater not getting warm enough and she was very surprised as even with the heat directed to the screen her feet were very warm

I did remember to test the washer but forgot the horns
Nigel Atkins

Regarding silicone spray, keep that stuff away from electric motors and switches because in the presence of ozone (which results from even very small electric arcing), silicone dioxide is produced: sand. It ruins motors and switches in modern cars in which have used too much silicone based cleaners inside of, or when manufacturers make the mistake of using silicone containing grease.

demerit points for my mixed up grammar above


Norm

Norm Kerr

thanks again Nigel and Norm, not sure about electrickery, must be a bit of computatrickery, my link should have posted to the Contact cleaner yours led to Nigel :-)
apologies, my mistake.
best, Dave.
DW Warren

it does now - bloody computers !
Nigel Atkins

This thread was discussed between 08/11/2013 and 12/11/2013

MG Midget and Sprite Technical index

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