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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - MGB Heater

I have a 1977 MGB with no heat. The car sat for years before I bought it. Got most everything to work but the heater. Heater motor makes blowing noises, and I can run water through the unit. But almost no air comes out and what does is not hot - just warm. I found the flap inside the box that directs air to windshield or feet rusted fixed and forced it into the feet position. (It is very hard to see inside while the box is installed.) Other than pull the whole unit out and take it apart, anybody got any ideas. Also, if I take it out, any suggestions for doing that.

On other issue. I have had Bs before and never appreciated the heater. Anybody got any ideas on how to improve it. It really needs a higher speed blower, maybe two positions. Or, has someone put a booster blower in? Or, has anyone thrown out the whole thing and found something better.

Thanks,

Bill M
Bill Martens

The problem is almost certainly poor water flow through the valve on the side of the cylinder head. See Bob Muenchausen's website for details on how to make dramatic improvements. http://members.aol.com/bobmunch/index1.html
Mike
Mike Howlett

Here is the direct URL to that site for anyone reading this: http://members.aol.com/bobmunch/HTRVlsHT.htm
And thanks for the recommendation, Mike!!!
Bob Muenchausen

It must be be getting colder outside becasue of the threads appering about the naff heater in the B! :-(
Ian Holllday

The 77B does have a 2-speed switch. Halfway down is slow, all the way down is fast. Try backflushing your heater core for optimum performance, as well as doing Bob Munch's mod to the heater valve. I use a small diameter garden hose with the brass end cut off and hose clamped to the heater box to backflush. Every time I've done this, I got a bunch of rusty crud out, and the heater worked significantly better. Also make sure you have the correct thermostat installed.
Paul Konkle

ditto Paul..at least first backflush the heater core..I got about a pint of thick rust-colored mud out of mine!
BobT SC

Veery useful info from Mr Munchenhausen. Just as an aside, early midgets had a valve which was actually like a tap which I believe would fit directly onto mounting bolts on the head, but would not give cockpit control of course.
T Green

To followup on T. Greens statement regarding using a Midget heater valve my Moss catalog shows four parts required for the valve:
1. 360-400 The heater valve
2. 324-065 Washer
3. 360-415 Heater valve base
4. 296-455 Gasket
The valve itself is listed as applying to the 948-1275cc engines (no car dates given). The valve for the 1500cc engine is N/A. No mention of if this would fit a B series engine or not. A call to Moss might answer that question.
In my opinion if it did fit it would depend on what materials the valve was made from. If the same as the normal B type (diaphram) I'd forget it. If it was a ball type valve I'd consider it. FWIW

Mike
'79B
Mike Janacek

Use a kettle descaler. Pass the fluid thro several times It works well!

Tony

Tony,

When you wrote about a "kettle descaler", I conjured up immediately what you were writing about. However, is this a product easily accessible and does it have a brand name???

Cheers - Dennis L. Rainey - Sacramento
Dennis Rainey

Do all or any 75's have a two speed fan switch? I don't know if my switch is just very stubborn or if its just a one speed switch. The heater works well otherwise. If I had to guess, it would seem to be a "low" setting relative to noise and output.

TIA
Luke
Luke Staley

My '75 has a one speed switch. My dad's 78 had a two-speed, where the "low" speed sounded and felt like my car's only speed.

My bet is the two speed switch happened with the dash change in 77.
Aaron Whiteman

Aaron-
You're right. According to Clausager's "ORIGINAL MGB" the two speed fan switch was in fact first introduced for the 1977 model year.
Steve S.

I looked into the Midget valve, and decided that it was OK, but probably not sufficiently better than what I had come up with in my ignorance of it. I tend to prefer ball valves of the sort described in my Web site as we had excellent service from them when used in a large office building boiler/heating system. FWIW.
Bob Muenchausen

Steve S.

Is it possible to "just" upgrade the switch to a two speed? Or, do I need an upgraded motor? Are the one speed motors most like the high setting or the low setting on a two speed? I have no interest on turning the fan slower than it already blows.

Luke
Luke Staley

To clean out my heater matrix, I bought a bottle of CLR from K-Mart or the hardware store, and took the felt pads off the sides of the fins. I then filled the matrix about half way up with full-strength CLR and capped off the holes with aluminum foil and rubber bands. I let that sit, slushing it around every now and then, for an hour or two. After pouring out the CLR, I rinsed it several times in clean water, straightened out any bent fins on the exterior and glued the felt pads back in their original positions. While I was waiting for the CLR to eat all the rust and scale inside the matrix, I wire-brushed and repainted the heater box woth a few coats of black Rustoleum.
Now I have a very clean heater core and a nice looking heater box to spruce up the engine bay. It all took about 3 hours.
Paul Alimia

"Is it possible to "just" upgrade the switch to a two speed? "

If you do that you will have to add a resistor in order to get two speeds, which will result in 'normal' and 'slow' speeds and be about as much use as the instrument lighting rheostat.
Paul Hunt

Mr. Alimia,

Anyone else talks of the car being built around the heater box. You removed the box, cleaned the matrix, painted the box (with multiple coats) and then reassembled and replaced it in three hours? What part of the story aren't you telling us?


Matt K.
Matt Kulka

Paul,

Thanks, that was the answer that I thought I might hear, but wasn't wanting to hear.

Luke
Luke Staley

On my wife's Gt I did a conversion that I swear by. I took off the heater valve. Cut a piece of steal to fit in place of it. Drilled and tapped said steel to pipe thread. Installed short nipple and elbow followed by longer nipple. 1/2 inch hose goes to heater from there. On return hose from heater I installed an in line cable operated heater valve. Results= No heater valve to drip on Dist or restrick flow. Also new valve uses globe valve so that you can actually adjust water flow to control temp. This heater will run you out down into the teens. New valve works with much less friction. Only way to go!!! Bob
Bob Thompson

Bob, what heater valve did you use? Do you have a part #?
Michael Wish

3 hours to refurb the heater - ha! three hours to get it off.

I have had problems with cable stretch - have you checked whether the lever on the heater valve is moving when you turn the control knob? It can get stuck.

MGOC (I think) used to sell an 'uprated' (aluminium) heater matrix and an 'improved' fan motor/rotor. You may be able to get more airflow by using the fan rotor from a more modern car (Metro, I think), although it may be difficult to find one in the US.

Are the fan connections on the right way around? The fan will turn, but output will be pathetic.
Neil

Bob Thompson(NC) has another good solution. Just one of many possible alternatives to come out of people's experience.

One thing that would make it easier for others to copy, Bob, would be a little info on which valve you used (some folks just want to go into NAPA and ask for part # .....) and maybe a photo somewhere so that folks could copy/print your photo and show it to the guy behind the counter.

I think it is a great idea, and if it works with the temp control, then so much the better. FWIW
Bob Muenchausen

I bought a heater control valve from one of the vendors at the Lowe's Motor Speedway
Auto Fair in September. I saw Bob T's car at the Loch Norman show about a month
ago but didn't notice the heater valve. I bought mine with the intention of doing as Bob
did but to put in on the inlet hose. I have a part # but I think it is a vendor part# and
there is no manufacturer's name, it was made in Mexico # H38C-2211-030. It is for
5/8" hose so it will require some hose streching to fit it. You can see front and rear
photos of the valve a Photo Point. Remember you will need to copy and paste to view
them.

http://albums.photopoint.com/j/ViewPhoto?u=817566&a=13849223&p=55020256&f=0

FWIW, Clifton
Clifton Gordon

Guys;
First let me make it clear that is not my car!! I'm just allowed to work on it. Once in a while she even lets me drive it! Hear you go NAPA #660-1141. Workd great. is 5/8 so had to use two reducers which i also got from Napa. No part #. Clifton, Why didn't you look me up I was at the tech tent all day as Another guy from a parts house and I did the tech stuff. Would like to have met ya. I beleive Old air or vintage air offers versions of this valve as well. Bob
Bob Thompson

Hi,
Turn off the fans wait for a minute and turn it back on. If you get hot air for 10-15 seconds it's the heater core. Eventhough you can pour water through the core it may still be pluged . But with the fans turned off the coolent slowely passes through the few tubes that may be clear and heats the Core. I have seen this many times. If you are good with a propane torch you can remove the top tank and cleane the core tubes

cec

Cec Fry

Bob, Sorry for calling it your car, I knew it belongs to your wife. I did stop by
and talk to you about the metal MG fans but I dumbly neglected to introduce
myself. I shouldn't have expected you to know me. I'll make sure I yell my
name the next time I see you. If you can't place me I was probably the oldest
guy there and had my sons Jensen Interceptor at the show.

On the heater valve I suppose the reducers would insure a better fit than
trying to strech a 1/2" hose over the 5/8" valve.
Clifton
Clifton Gordon

Follow up on heater valve. The heater valve I bought is reversed from the MG heater valve.
In other words to use it when the heat knob is off the heat will be on and when the knob
is at hot the heat will be off. The MG valve must be pushed to turn heat on, the valve I
have is pulled to turn it on. Otherwise it should work ok. I think it would be best to use
a choke cable, pull out for heat and push in to turn heat off. FWIW, Clifton
Clifton Gordon

Clifton and friends;
Had same problem with valve backwards. just bring cable in from other end and make up outer cable support useing plastic wire ties Bob
Bob Thompson

This thread was discussed between 21/09/2001 and 13/10/2001

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