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MG MGB Technical - Heater. Don't make me remove it.

Since i have owned my B, the heater has never worked. Fan didn't work, seized cables etc. It never bothered me since when i drove in colder days, the heat from the floor was enough, but last year i got caught in a big rain storm and the windshield fogged up on me. Just a little scary not seeing anything.Time to fix it.
Well, the fan was simply poor dirty connections in the switch. But i still don't have any air flow. To the floor it is minimal, and to the windshield nothing. Reading the archives, I switched the fan wires and still nothing. The control for the air flow will move from off to floor easy enough, but moving to windscreen is difficult. All the hoses to the vents are attached. the heat control cable and heater valve are not attached. This may be silly but, if the hoses to the heater box are not attached will that make a difference? According to the archives, the problem could be the control cables, but they can only be reached by removing the heater. I've also heard this is a nasty job. Please don't make me remove the heater:(

Ken
70 B
Ken Harris

Ken

Well, it is not easy, but you do not HAVE to pull the heater to work on the control cable. Take the passenger heater vent out and you can see the cable. Should be able to tell if it is hooked up and if it is working. If the cable is broken, It is a tight space, but you can get to the clamp that holds the cable.

It is a bit hard on the back and neck, but beats pulling the heater.
BEC Cunha

On the plus side, its a character building job.
Roger T

"It is a character building job"

Roger, would that be the Humpback of Notre Dame character? After getting into, then out of a position that allows you to work under the dash that's how it feels

Ken
Ken Harris

ok this is probably not good. I contorted myself enough to see inside the foot vent. It is really rusty in there. I can see the cable is moving fine, but what it is moving seems to be missing something. There is a metal piece attached to theh cable, but it doesn't seem to "block" anything. I can see the hole where the air is suppose to come out of, and nothing gets in it's way, or diverts it in any way. I think i see a hole in this pice of metal where something may have been attached.

Is there something else that is supposed to be in there? It looks like the heater is coming out right?

Ken
Ken Harris

Sounds like the heater will have to come out, sorry. What should be attached to the cable is a flapper valve which directs the heated air either into the footwell or up to the defroster outlets, which it sounds like you need. Check out this link http://www.victoriabritish.com/icatalog/mg/0110.asp to the VB catalog, it shows the lower portion of the heater box pretty well (item 4) with the flapper valve shown in the middle position which allows the air to flow out into the footwells. Follow the lines up to items 37 and those are the outlets that feed the defrosters. The flapper must rotate to close the bottom of the box and force the air out the side where those fit. If you get everything working as new and still want more air flow then there are mods to install a GM 3 speed blower in the B box which does blow a lot of air.
Bill Young

From the engine compartment, try taking out the motor and freeing up the fan assembly. Squirt it with some WD-40. That's all I did to mine and now it works fine. What I still don't understand is that it didn't blow fuses when it was frozen or locked up (which is the way it was when I got the car).
Tom Fisher

Woo Hoo!!! I have air flow. Thanks Bill for that link to VB. It turns out the flapper was rusted shut, which is why it looked like something was missing. I managed to pry it open, so now I have air flow. Not alot to the windscreen, but if i close the footwell vents it is better. As i said before, i never use the heat much and only really wanted windscreen air. Now, hopefully when it gets back together i will also have heat???

Thanks everyone for your help.

Ken
Ken Harris

Check out the thread:

you won't believe this one...

in MGB General. When you go to the link Bob mentions, look at his work on MGB heaters. There is a lot of info there to help get you some heat.
C Holm

Well, yes and no Ken. You have probably advanced a couple of incarnations already.

I have to admit that when I did my heater overhaul I took advantage of having the engine/box out for a clutch change. Made it just so much easier being able to stand in the engine bay. Note, easier NOT easy.

With the underdash stuff I learnt it really was worth pulling the seats and lying on the floor with an old pillow against the firewall/pedals supporting the head/neck. Just so much more tolerable dealing with the control mechanisms and flap-end connection through the foorwell flap (which I also took off to make it easier to see in, as much as to operate in there.

The elbows which carry the airflow to the tubes connected to the dash vents connect to the lower heater box via plastic tubes. These reside behind the removeable plate in the face of the structure immediately behind the speaker housing, above the tunnel. If these are mis-aligned or missing you will interfer with airflow to the screen vents. (On my car the heater flap control cable also passes through this plate, in the top RHS corner area.)

The fact that you have found a rusted flap, and the heater tap is not connected, suggests a past history of the heater matrix having let go. Prudently you might pull the heater box and give it an overhaul or, as a minimum, be able to see from the engine bay side whether there are other rust issues to do with the plenum chamber and its drain pipe. The pipe passes through the spaces occupied by the heater box flap section and the concealed tubes I mentioned connecting the screen duct pipes to air source.

Good luck with it. Difficult and cramped spaces and all, but quite do-able if you take your time and think through each challenge as it crops up.

Just one note of warning. Mine was a 14 bandaid job - watch out for sharp, pointed metal edges/spots all through those spaces. In my experience, this was not an area the company spent anything on in terms of cleaning up after stamping/pressing.

Regards
Roger
Roger T

As to whether you will get heat that is a completely different issue to air volume, depending on coolant flow through the valve, matrix and return pipe. And even when you have that it is dependant on the air flow being through the matrix itself, i.e. not blocked with debris, and not bypassing the matrix altogether due to a rotted foam seal 'tween matrix and casing. It is possible to remove the heater cover without removing the whole heater unit, with a bit of distortion of the cover.
Paul Hunt 2

Remove it...It was easy...and I refurbished everything in the process...works like new...and got to clean up a little rust..etc...
pete

I think i am going to remove the heater. I got thinking today, why am i so excited about forcing open a badly rusted flap. I should be concerned with WHY i have so much rust and getting rid of it. I also noticed there was the foam seal detrioated and falling out as well.

Since it is still %@%## winter here, with no warm weather on the horizon, I might as well just get it over and done with, as it will have to be done sometime.

Roger, yes i agree that anything under the dash usually involves band aids and swear words.

Wish me luck

Ken
Ken Harris

As said before, you can access the cable through the passenger heat vent. But, do your self a favor and pull the right seat out. Even with a little more room going for you, it is advisable to make sure no one else is around when doing the job! Aside from standing on your head with your arms in a cramped position, you seem to pick up a few unfavorable words while doing it. But, it can be done! PJ
P. Jennings

Further items are leaves blocking the outside intake vent below the windshield, and the ever amusing mousie nests - they LOVE heater boxes and air ducts. They pee on everything and it may be the most corrosive mix ever - it eats steel, brass, copper, aluminum; all the while they eat seats, carpet, insulation and wires - and air (brake) lines on big trucks. They are known to fill heater boxes, air filters, inlet manifolds, exhaust pipes, mufflers, and even the inside of cylinder bores with nuts, seeds, berries, and dogfood - Yes they can most certainly get into a cylinder past an open valve; a motorcycle mechanic I know used to do a couple of rebores every spring from that. Somewhere a couple of years ago I posted the story of the MGB that would not start after the carbs were off for two weeks - After taking the head off, I cleaned out pounds of dogfood from the manifold and a couple of cylinders; when started it blew a 25ft stream of the same out the exhaust. Canada? mouse winter heaven is an MGB! And we once found the entire rear boot of a long-term Bugeye project FILLED with dogfood - about 400 lbs! DO NOT keep your dogfood in the garage!!!
FRM
FR Millmore

We do have a mouse population here,with a house facing onto woods you just have to live in peace with them. The funniest recent happening was finding an enterprising harvest mouse had taken up living in one of the rabbit hutches. The most irritating that they had eaten some cotton from the wiring loom, thankfully no pvc insulation though. When I sent some pics of the overdrive relay the flash revealed sunflower seed husks stored against future needs in the unused LHD steering column tunnel on our RHD car. These were invisible under normal light.
Stan Best

This thread was discussed between 11/04/2007 and 18/04/2007

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