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SP250 heater/demister

SPortsman
Posts: 34
Joined: Sat May 01, 2021 11:42 am
Location: France

Re: SP250 heater/demister

Post by SPortsman »

There's a thread on the old forum here showing the mounting and it includes a link to a rebuild article.

Martyn Ross
Posts: 64
Joined: Tue Feb 02, 2016 7:46 am

Re: SP250 heater/demister

Post by Martyn Ross »

Many thanks to all who responded - all your answers were a great help
The unit is now out - interestingly held in by only one bolt. The metal tubes which channel air to the demister hoses were riveted to the box, so removal had to be made possible by unbolting the accelerator thingie (as in photo) so I could slide the box forwards.
Now all I have to do is insert the new matrix and find out why the fan don't go very fast.
Attachments
IMG_2362_LI (2).jpg

Martyn Ross
Posts: 64
Joined: Tue Feb 02, 2016 7:46 am

Re: SP250 heater/demister

Post by Martyn Ross »

Much thanks to all who have helped on this thread.
Replacement (new) matrix now in place. You may recall that when I started this thread there was not a puff of air emitting from the heater or demister when the blower was switched on. I've looked at the motor that drives the fan - connected to 12V and it whistles round beautifully. I was puzzled - until I realised it might be working in reverse - having converted to negative earth when electronic ignition was fitted. I was pondering on how stupid I could be, simply reverse the connections and Hey Presto, it's done. Reassembled into the heater box and wired the way it always was it did indeed give a fair gale the wrong way. Problem solved I thought, reverse the connections and ... it did the same.
The photo shows the rotation of the fan, which is the with connection made either way. A solution would be to reverse the fan on the shaft, but that's not possible.
Is there a solution out there?
Attachments
sp 250 heater fan_LI.jpg

Ian Slade
Wise Man
Wise Man
Posts: 792
Joined: Sat Feb 13, 2016 9:54 am
Location: Sevilla Spain

Re: SP250 heater/demister

Post by Ian Slade »

I don't get this if you changed from +ve earth to -ve earth there should be no difference in rotation direction as it is a compound motor, I would suggest the motor is from a different car or the fan is, the only solution is to dissemble the fan motor disconnect and swap the field coil wires from the brushes and swap them over, while you're at it add another wire a two position switch between the motor switch with a resistor from a modern multi speed fan in line with one side of the switch, you can pick which speed you want from the tappings or use the modern fan switch to pick multi speeds but the circuitry becomes more complicated and find space to fit.
Owner since the 70's, Genghis is slightly to my left.

Ian Slade
Wise Man
Wise Man
Posts: 792
Joined: Sat Feb 13, 2016 9:54 am
Location: Sevilla Spain

Re: SP250 heater/demister

Post by Ian Slade »

Just information to those who would like modern facilities without changing original parts, with electric motor driven facilities the speeds can be increased by adding resistances to the field coils, this requires the one of the field coil connections at the brushes to be disconnected and a second wire via a switch and resistor(s) back to the field coils.
Note, you will need to check the amps drawn and multiply by 13 to get the correct value of resistor wattage, to check the speed required a 10 Watt 20 Ohm variable resistor or potentiometer is required
Warning the resistors can get hot so their position and or heat shield needs to be selected so as not to cause a fire. ( the SP is mainly GRP and wood both inflammable)
motor wiring12122021.jpg
Owner since the 70's, Genghis is slightly to my left.

#100910
Posts: 92
Joined: Sat Feb 13, 2016 2:32 pm
Location: Austin, Texas

Re: SP250 heater/demister

Post by #100910 »

On my unit both the direction of rotation and curve of blades are opposite of yours.
The Smiths part number on the motor reads: FHM 5332/04

There is a battered unit with good images on ebay:

https://www.ebay.com/itm/304045502320?h ... Swn5lg1jwC

Ian Slade
Wise Man
Wise Man
Posts: 792
Joined: Sat Feb 13, 2016 9:54 am
Location: Sevilla Spain

Re: SP250 heater/demister

Post by Ian Slade »

At that money it's cheaper, quicker and easier to swap the field coil connections over
Owner since the 70's, Genghis is slightly to my left.

Martyn Ross
Posts: 64
Joined: Tue Feb 02, 2016 7:46 am

Re: SP250 heater/demister

Post by Martyn Ross »

Dickie 9WVO history (1).pdf
(590.37 KiB) Downloaded 36 times
As ever, thanks for the responses.
Thinking back I can't recall the blower working properly since I purchased the car. 9WVO had a rebuilt front end after an incident in 1988 (see attached file - Ian's comment is pertinent!), so the polarity conversion is probably a red herring. My guess is that the heater/demist unit - or maybe just the motor and/or hamster wheel came from a different type of vehicle and so is the wrong type - Greg's comments support this theory. I'll be swapping the field connections over and see how that works, it'll probably work quite well even if the vanes on the fan are orientated incorrectly.
Having looked at the motor unit I'm at a loss to see how it comes apart - so yet another question here?

Ian Slade
Wise Man
Wise Man
Posts: 792
Joined: Sat Feb 13, 2016 9:54 am
Location: Sevilla Spain

Re: SP250 heater/demister

Post by Ian Slade »

From what I remember but not sure, there were two types of motor fitted to 50's and 60's cars , both look the same but one is riveted and the other has two long screws holding the two halves together,
Undo the two nuts and split the casing, think the brushes and field coil connections are on the nut end, if riveted type drill out the rivets split the casing then either pop rivet or source two long screws/ stud bar and nuts and reassemble
Owner since the 70's, Genghis is slightly to my left.

SPortsman
Posts: 34
Joined: Sat May 01, 2021 11:42 am
Location: France

Re: SP250 heater/demister

Post by SPortsman »

P1070478.JPG

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