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MG Midget and Sprite Technical - Heater valve - GAN5

Hi folks
Currently I have the remote type of heater valve fitted to the cylinder head, similar to that used on the Morris Minor. It should be operated by a stiff wire bowden type cable. The heater knob in the car merely works a flap in the fresh air ducting. There is a separate switch for the fan.

Should there be some sort of linkage between the flap in the ducting and the heater valve, or should the valve actually be the tap variety that needs manually opening or closing under the bonnet?

The car is a 1971 midget III, GAN5 91512. This seems to be one of the crossover cars, that had a few older parts fitted to the new revamped model just appearing!

Thanks in advance for your help!

Dom.
Dominic Excell

I have a 71 Sprite. For what it's worth (the po/rebuilder obviously was lost without a handbook)I have exactly the set-up you describe. There is no link between the flap and the valve. I guess the logic was that you might want the flap open on a warm day without heat, or open on a cold day with heat!
Comparing that with the multi-sensor different temperatures each side on my modern, it was wonderfully simple!
G Williams (Graeme)

Additionally, being able to vary the amount of opening whilst the heater valve is fully open, gives much more variable control. Reducing the air flow will increase the temperature of the heater, whist if it is getting too hot then opening up the air flap will bring the temperature down a bit, especially when travelling at speed. By comparison the water valve does tend to be an all or nothing affair giving little precise control of the heat produce.
Guy Weller

Midgets never had heat adjustment from in the car.
Always a heater tap to be operated under the bonnet.
Onno K

Thank you all so much for the input, I must now look out for a heater tap. Dom
Dominic Excell

Dominic

Try this link to Ashley Hinton part on eBay. I bought one a couple of years ago. It is good quality and has worked fine.


http://www.ebay.co.uk/itm/MG-MIDGET-AUSTIN-HEALEY-SPRITE-MORRIS-MINOR-HEATER-TAP-PART-NUMBER-88G588-/251231260896?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3a7e8cd0e0

Cheers

Tony
Tony Brough

BINGO!

where's Lawrence

Dom,
either you or me is getting confused

heater tap is on the cylinder head

original switch to operate the fan is also the cable pull for the fresh air to heater valve

you can not turn the blower on with the fresh air flap closed (pulled into the cabin from the dash0

often the electrical switch part doesn't work so an additional switch is added for the blower by a previous owner

from '66 onwards the operations remain the same for all MK3

the Driver's Handbook will explain all this to you as it's not that obvious despite what Guy and Lawrence and others think plus this book will tell you loads more I thought you had a copy
Nigel Atkins

Probably me being brain dead after a hard day at the office Nigel. My car has a heater tap on the cylinder, similar to but not identical to that found on the 1098cc Morris Minor. I have what looks like an original switch next to the choke, which operates the fan. The push-pull knob to the right of the chrome MG badge merely opens or closes the flap valve in the trunking under the bonnet. I'll have to venture out into the garage to retrieve the handbook, but as you say PO's have changed things over time.
Another question: the reset knob for the trip meter is missing, just a thin metal rod too small to grip remains. Is the knob merely a push fit, or should I glue a knob in place? Can't quite work out if it's a twist or push reset.
Thanks all!
Dom
Dominic Excell

Dominic,

The trip is a push up and turn/twist to zero.

The trip knob is fixed to the shaft by means of a pin through the shaft - often these shear off leaving just the spindle shaft.

R.
richard boobier

Thanks Richard - I think that is precisely what has happened here.... Looks like I'll have to get my thinking cap on to work out a fix for it. I like to use the trip meter to easily monitor the distance between refuelling.
Dominic Excell

Dom,
I was being distracted at my last post

some owners fit a Mini type heater valve, I think you'd recogonise it though, last few we've seen on cars for sale seemed to have the Mini valve but not the controlling wire

I should have also put chrome bumper Mk3 as the rubber bumper cars are also Mk3s

we went through how the heater operates on here before and unsurprisingly some of those without the benefit of the Handbook didn't quite get everything right

I've always put that many new owners, especially if they're young, won't fully know how the heater works, to stow the hood or possible how to use the choke

photos of your dash will help to see what's as original (or comparison with what's in the Handbook0

I've used tripometers in cars to tell me roughly how much fuel I've used but as I broke the trip spindle whilst putting the speedo back in on my Midget I now just use my fuel gauge - when working correctly they're pretty accurate

bear in mind a very full 'tank' is still probably less than 6 gallons
Nigel Atkins

Thanks for the reply Nigel. Yes, my heater valve is the cable operated type, complete with a couple of inches of unattached cable! I'll take some photos at the weekend when I have good light to play with.

Yet another question... (whenever will they end?!?)
I am replacing the rather nasty thin pancake air filters which apparently do nothing for performance. I have the original saucepan types which I intend to refit. However ... there is a brake servo fitted where the rear "handle" needs to sit.
Would it be causing problems to the running of the car - unbalancing the operation - if I were to shorten or even remove the rear intake pipe?

The filters currently in place look pretty clogged, so I have just bought new old stock filter elements for the "saucepans" in the hope that this will help smooth out the running when the engine is cold. At the moment, until it has warmed up for a few mins, it tends to backfire and lose power on acceleration, involving quite a bit of juggling with the choke. The P.O reported that it had gradually started behaving this way over the last 2 years.
Old cars are SO much more fun than new ones! :-)
Dominic Excell

Definitely ditch the 'pancake' filters.

You could shorten the filter intake, or you could remove the servo. They were never fitted as standard and don't improve braking efficiency, only reduce the amount of pedal pressure required.

Servos were optional on MGBs and I had considered adding one to mine. The general consensus is that they aren't necessary and it is one more thing that can - and does - go wrong.
Dave O'Neill2

I'm with Dave about removing the servo, I was thinking this about Rylan's car

if you'd have posted under bonnets photos before we'd have pointed out these things as when look at Rylan's selection pancake filters, unconnected Mini heater valves can up too so it shows a trend of fashion at some stage

I'd clean the 'pancake' filters or change them straight away, even if it's only a few days away that you're changing them I'd still clean the 'pancakes' for the sake of two days of travel, plus it's eliminating one problem at a time to see the result

going to standard filters is fine as their paper filters are cheap enough (if you buy from the right places) so there's no reason not to regularly change them - but many owners don't bother

your 36k-mile service should pick up why you have a backfire and lose of power, sorry but I'll have a small bet it not just the filters that need attention

as it happens - the Handbook has the service schedule and details of how to do the jobs, it wont cover non-service item parts though

did the PO mention what servicing was done and how long ago and how many miles traveled in between?

keep driving it but get that service started as soon as you can

if you want some non-technical, non-mechanical general notes just email me
Nigel Atkins

Interesting comments re: servo - I removed a defective one from the Morris and reverted to standard set up when I replaced the entire system. I will probably go down that route in due course with the MG.
PO did small bits of servicing, mainly just keeping fluids topped up as needed (not much needed with a newly rebuilt engine) He has also reported that he thinks a carb needle sticks occasionally. A new needle and jet might be needed I think.... The car has only driven 3000 miles since rebuild and therefore I think fluids were never replaced. I've already made a start, coolant is replaced, and the oils will be this weekend.
I'll email you tonight Nigel, your notes would be most helpful, thanks!
Dom
Dominic Excell

Dom. When the PO said there was a sticking needle, he was probably referring to the needle valve in the float chamber rather than the needle in the jet. If the needle valve sticks open the float chamber floods and may cause two cylinders to run rich. If it sticks closed, it causes fuel starvation and two cylinders will run lean or stop firing. Either way will result in rough running.

Bernie.
b higginson

If the car has had only minimal servicing, then take Nigel's advice and do a full 12,000 mile service. And I would pay particular attention to greasing the front suspension points as they may well have been neglected for years and are easily ignored until it is too late!

I agree the comments about the servo. To me they are just "bling" on a Spridget. They may make the underbonnet area look more purposful but they are completely unnecessary on such a light car.

As for heater valve, if the fan is now worked from a separate switch, and the push-pull knob is connected to an aftermarket water valve, then what is controlling the air flap on the ducting? The air flap is what gives the fine temperature control. Are you sure that the push-pull knob isn't still the correct one with the incorporated switch for the fan? It may have just been disconnected - and easy check would be to look / feel for the connection terminals on the back of the switch.
Guy Weller

I do not completely agree with the comments on a servo being useless on a spridget.
Correct it doesnt improve your braking, it only cost less effort pushing the pedal to stop.

Having doen a couple trackdays with my modified car(almost 3 times the BHP a usual spridget has) I noticed I had to brake earlyer then the other modern cars like MG ZR.
My car is lighter and should be easier to bring to a hold then theirs and I have modified brakes too (4 pot on vented discs).
So basicly technical they are not better and I should be able to outbrake them.
Im just not comfortable to feel like I have to push the brake-padle thrue the floor to get to a stop and thats why think I can brake better/harder with less physical effort and feel like I can controll the brakes better thatway.

Ofcourse I still have to find out if my theory is right once ive installed the servo on my car. ;)

But if your used to modern cars with servo's I guess servo brakes on a standard Midget will make it "feel" alright and do not underastemate the importants of "feel" for comfortable driving. :)
Arie de Best

3,000 miles since the engine was rebuilt but when was that, it should have had a good few oil and filter changes as a rebuilt engine and by the fact it does such little mileage, more so if the journeys were all short

even modern cars have additional servicing intervals for low use

I suggest a 36k-mile especially on a vehicle like this where the PO tells you very little has been done including using it

where the PO says a sticking needle he may just be guessing and the fault might be due to lack of servicing, cleaning and/or use

doing the servicing will improve the whole car and will pick up and repair faults and help prevent actual or potential future faults and driving the car should help discover any that the service doesn't

I'm sure Dom will have a fine running car by summer if not before and by this time next year most issues will have been dealt with
Nigel Atkins

Will be doing a very thorough service over the next few weeks - one thing the PO did very well was keep the kingpins & trunnions well greased. Car needs to be fully serviced by Easter, as we've a major re-furb on the dining room starting immediately after. Just looked at the servo set-up - looks easy enough to remove it and replumb the brake lines. Guy, the push-pull knob does operate the flap - the heater valve (which I've noticed is seeping slightly - good reason to change it!) is just sitting there looking not particularly pretty! You have to manually operate the lever.
Photos to follow.
Dominic Excell

>>Car needs to be fully serviced by Easter, as we've a major re-furb on the dining room starting immediately after.<<
what! you can forget that you've got a Spridget now to spend your time, energy and money on and anyway you'll be out driving it enjoying the fresh air not stuck indoors renewing chemicals, the quicker you decorate the quicker it deteriorates, leaving it another 10+ years and you've saved one redecoration cost

you know it makes sense
Nigel Atkins

only 10 years?!! We plan on making the decorations last a long time, with vintage wallpapers etc - taking the house back to it's original glory and undoing some of the horrors inflicted on it in the 60's and 70's.
Dominic Excell

Under-bonnet and dashboard photos.


Dominic Excell

very strange - the under=bonnet photos although uploaded have failed to appear....
Dominic Excell

Under-bonnet


Dominic Excell

The plastic fuel filter will be removed, as will the pancakes. The choke cable looks to be very tight too.


Dominic Excell

The heater valve


Dominic Excell

The push-pull knob operates the flap correctly.


Dominic Excell

Dom,
you can only put up one photo per post

the dash photo looks familiar so perhaps you put it up before as I remember commenting on the bonnet pull being in the way of the shelf and should be fitted to captive nuts on the side of the g/box square and we discussed the steering wheel and size, the dash layout looks standard to me

that servo fills out the engine bay

I note a newish (Kevlar?) top hose, is it crazed yet?

battery earth at body is rusty(?) never a good idea (clean, secure, protect)

keep a fuel filter as it does a job and lets you at least see the fuel has made it as far as the filter, plastic is cheap and easy to use and replace at 12k-mile/annual service

another newish heater to valve hose check it dont trust the recent rubbish rubber

whats the electric relay for?

Nigel Atkins

Nigel, firstly thanks for the reams of information, very much appreciated.
Yes, the battery connection will be cleaned and protected shortly, as will all electrical connections. Hoses are fiune at the moment, having been fitted by PO within the last year.
The relay is actually a battery isolator switch, reached from within the cabin.
Since buying it, my inspections so far reveal a very sound little car, with just insignificant problems or gremlins to be sorted out. Nothing too frightening! It's the rust that frightens me mostly. Having re-engined a Morris Minor, and replaced entire braking systems on both I have owned, mechanicals don't hold much fear for me anymore.
That servo is going soon. It looks far simpler to remove than the one on The Morris, which involved most of the piping being changed.
Thanks again for your great help,
Dom
Dominic Excell

Dom,
no problem, the notes might not tell you much but dont be put off using modern oils or fitments on an old car that youre going to use a lot and possibly rely on for commute/work transport the first thing I changed on mine was the fuel pump as although it worked I didnt like the look of it and it was the SU points type, Ive no interest in kneeling on the ground trying to hit it with a hammer to see if I can get a few more weeks of life out of it, I swapped it for a Q&H ordinary looking electronic model for about two thirds the price of the proper pump

dont be too precious about it remaining too period

when I got my Midget coming up to 6 years ago had a new looking ordinary rubber top hose but it was cracking so I swapped it for a new Kevlar top hose and crazed within 9 months, having experienced a lot of rubbish rubber on my previous classic I swapped to a silicone set and as the advert said fit and forget

Im sure any problems you get will be minor wrinkles mainly because of its lack of use and servicing remedied as I put earlier

as for protecting against rust see the Archives there are many different products and idea of what to do and use again frequent use of the vehicle can actually help in certain ways and times

Im sure after a couple of months of use and after the servicing the improvements will be measureable to now and the car even more fun
Nigel Atkins

Dominic,

The servo / no servo is a continual debate on this forum and there is no one correct answer.

I mainly drive my daily modern and many new cars are so over servo'd that very little effort to do an emergency stop - try some recent Golf's !!
My SAAB Aero has dinner plates for discs / servo etc but is more progressive a feel.

I find changing back to the Midget takes me a long time to adjust to the greatly increased pedal effort required - too long for safety IMO.
When the Midget was my only driver I did not have or feel I needed the servo.

The servo I have fitted to the midget is only a fairly low ratio one and I find the brakes much more to my liking changing between cars. It does not improve the braking - just reduces the effort on the pedal.

And no I don't find it reduces brake feel at all as the servo advantage is not like found on VAG cars etc.

Very much how it feels for you sort of thing.

R.
richard boobier

I'll be monitoring the hoses very carefully Nigel - remember I'm used to running a Minor, and the new rubber parts are as bad as those for the Midget. For instance I had to replace rubber suspension bushes a mere 6 months/500 miles after fitting as they were almost worn through in that short time. I have no problem with original type pumps etc, occasional servicing of the points and they run forever. Easy to fit new points and diaphragms too! Again constant use keeps them working well.
Richard, I am well used to switching between a servo'd Fiat 500 and a non-servo'd Morris, somehow one just gets into "Morris Mode" (now Midget Mode1) or Modern car mode. Mind you our previous car, a Micra had such ridiculously powerful brakes you'd almost somersault it in an emergency stop! Grossly over-servo'd. I found that far more difficult to judge the braking effort req'd. I rather like the idea of having more space under the bonnet for the original air filters, and one less thing to go wrong! Also the servos are quite sale-able on ebay! Especially as it's a Lockheed.
Dom
Dominic Excell

Dominic,
Are you aware that the push - pull knob that operates the air flap also acts as an electrical switch to control the heater fan? At least that is how it is supposed to be set up. Do I understand that someone has wired the heater fan through the adjacent switch? (which should control on/off of the dash board lighting)

If the push-pull knob installed is the correct one it will have electrical terminals on the back. It works by turning the knob clockwise to operate the fan (when the wires are connected of course!). Sometimes people struggle with them if they don't realise that the switch is designed only to work when the knob is pushed fully in. This means the fan only works when the air flap is fully open. Logical, as there is little point in the fan working if the air duct is closed off.
Guy Weller

Guy,
Yes I am aware, the PO told me that the switch had been disconnected in the past, leaving the knob only to push or pull. The switch next to the choke knob now controls the fan. Without reference to the handbook, which is the car in a freezing garage, I am assuming that this switch should control the dash lights?
Dominic Excell

This thread was discussed between 19/02/2013 and 21/02/2013

MG Midget and Sprite Technical index

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