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MG MGB Technical - A/C and Water Pump

I have A/C on my '73 B/GT, using a Sanden compressor. It is a fairly common configuration where the water pump and compressor are driven by one belt and the alternator is driven off the compressor on a second short belt.

Problem: in order to keep the fanbelt from slipping when the compressor kicks on, the belt has to be tightened to the point where the water pump is jeopardized. I thought that I'd get by with it, but now after about 11,000 miles, my water pump is leaking. I'm trying to think of a better solution:

1. a larger pulley on the compressor? I can't find one.
2. better yet, a harmonic balancer with two pulleys on it? ' Can't find one of those either. Of course some of the water pumps have two pulleys, but that doesn't help, since I'm trying to get away from the water pump.

Any ideas anybody? Any way I can add a second pulley to the harmonic balancer?

Thanks for any ideas. And please, no wise remarks about tearing the A/C out. A/C is necessary for Navigator-approval!

Allen

Allen Bachelder

I doubt there is room for a second pulley on the balancer as the steering rack is close.

Is it possible to drive just the compressor from the crank pulley and the water pump/alternator from the compressor too?

Another possibility is to have the crank pulley machined to take a second belt - but you would need to have a plate made and fitted to the pulley to restore the weight lost through machining or else the harmonics will be altered.
Chris at Octarine Services

What about using the second sheive on those dual sheive crank pulleys used on Smog pump equipped US bound cars??
Bob Muenchausen

Sorry, didn't finish my thought. I was thinking about those smogged cars like mine which no longer use the air pump. That second sheive is just along for the ride if you don't use an air pump. Just a thought.
Bob Muenchausen

Thanks all!

Bob, the problem with the second sheive is that it is on the water pump - which means that the extra belt tension will end up right where I don't want it - on the water pump itself.

Chris: of course! Run the compressor directly off the balancer with what ever belt tension is necessary, and run both the water pump and the alternator off the second sheive of the compressor. Actually, using the outer sheive on the water pump INSTEAD of the inner one, I may be able to reconfigure the belts with no (or very little) modification to the mounting brackets. I would still have moveable components to adjust the tension on both belts.

' Will look into this shortly and report back.

Thanks again, guys.

Allen
Allen Bachelder

Have you tried sandblasting the pulleys? After years of use, the pulleys become polished and belts may slip. Used to see this a lot on old Volvos.
Kimberly

Auto storers sell belt dressing which increases the friction.
Dan Robinson

Hi Allen

I have similar idea to make another V groove on harmonic balancer and went with that idea to Romac (www.romac.com.au), company that produces high quality harmonic balancers, but they didn’t like that idea at all. I got tip, to replace all single V pulleys with multi V pulleys, and use single belt to drive them all. You can find basic set (water pump, alternator and crank pulley) at www.hi-flow.com/HPOP2.htm, but you will have to find pulley for your AC compressor, or maybe you can convince Moss to sell you only pulley kit that they use for the supercharger.
toni

Thanks to all of you for your help. This BBS is really terrific! My initial approach will be to try Chris's solution. I have tried belt dressing on another car - but it still required more belt tension on the water pump than the manuals recommend.

Cheers,
Allen
Allen Bachelder

toni

I assume that you are referring to the Power Pulley kit on the HiFLow webb site. It is not clear to me what this setup is buying you. Guess I don't understand the difference between single V pulleys and multi V pulleys.

Thanks

Larry
Larry Hallanger

Hi Larry,
yes I am talking about power pulley kit.
Single V belt is belt that you know from your MG. Multi V (or poly V) belt is modern version, it is flat on outer side but in inner side has many (6, 8, or more) small grooves. More grooves mean bigger friction area, so there is less chance that belt slips, what mean less stress for engine. It is also thinner comparing to single V belt and more flexible.
Pal from Romac has told me not to change geometry of standard harmonic damper, because changing of mass of the outer pulley (after rubber insert) will destroy its function. His suggestion was to make another single V pulley and that should be bolted on harmonic balancer (on inner part of pulley, under the rubber toward the center of crank). Anyway as Chris already mentioned, there is very limited space, so that is not an option. Recommendation from Romac was to replace original crank pulley (and also all other) with multi V pulley.
But it is not clear to me, how could be multi V crank pulley without rubber insert healthier for engine as standard harmonic balancer?
toni

What I did was run a belt from the crank to the A/C 2 grove pully & then the other grove on the A/C I went to the water pump & alt. I tighten the crap out of the A/C belt, & I leave the alt., water pump belt to std. tight. Running A/C on my 73 4cyl 3 years now (75k) on the same water pump. I had to space, shim the A/c comp. around 7/16 of a inch.
Glenn Towery

Sorry, Alan, I had it in my mind that the second sheive was on the crank pulley. Oh, well. Glen's suggestion is probably a better idea, altho a two sheive crank pulley would be ideal, if there were one to be had.
Bob Muenchausen

This is a little outside the box, but could your belt be slipping due to an overcharge in the AC system. You should not have to get a belt that tight to keep it from slipping. Just a thought.
Emmanuel Kafant

Again, lots of thanks to all of you. Emmanuel, your arguement makes sense, but I don't believe it is overcharged because it has slipped in the past even when it was a little undercharged. Also the pressure switch seems to keep it cycling normally. The belt doesn't slip all the time; mostly for a second or two at start-up and sometimes at idle.

It seems possible that a larger pulley on the compressor would help, but I don't believe they are available.

GLEN, it looks like you've done what Chris suggested as a possible answer. Question: as presently configured, the main drive belt from the balancer picks up the front sheive on the compressor and the rear sheive on the water pump. Do I use the spacers to move the compressor forward enough to drive from the balancer on the rear sheive? If I do that, and space the alternator forward enough to drive on the compressor front sheive, will that line up with the front sheive on the water pump?

' Sorry about all the questions but I don't see how else it would work.

Thanks!
Allen
Allen Bachelder

Allen, a question for you. Where is your condenser mounted? Ahead of the radiator or elsewhere? I have heard of someone mounting the condenser behind a ST air dam (the central air opening) rather than in front of the radiator. Not sure that is a good idea, but it may be more prevalent than I am aware of. What are your thoughts?? I am toying with the idea of adding A/C to my GT this spring and am trying to build consensus behind some of the options I have come across.
Bob Muenchausen

Bob's question is an interesting exercise. I'm putting A/C in my '73 this spring, and my plan was to just mount the condensor in front of the rad. To handle the extra cooling need, I'm planning on using a second (aftermarket) electric fan as a pusher in front to complement the new aftermarked puller behind the rad.

The setup Bob mentions might be a good alternative, for a lot of reasons - I can see pro's and con's. The consensus of options would be good to know.

R.
Rick Stevens

Bob,

My condenser is conventionally mounted in front of the radiator. I have two electric pusher fans in front of it in addition to the mechanical fan on the water pump. The electric fans come are switched in three ways:

1. through a diode from the compressor clutch circuit.
2. through the thermostatic switch provided which slips into the radiator core.
3. through an auxiliary fan switch on the console.

In actual use, the fans have never come on with the thermostat and I've never had to use the console switch. Perhaps there are times when operating with the A/C, if I were to turn the A/C off I'd find that the thermostatic switch was already on. But that would show itself when I turn the A/C off before shut-down, and it hasn't happened yet.

It seems to me the advantage of mounting the condenser down below is that the engine cools better. But I have not had any problem with the engine overheating on any B I've ever owned. Yes, in really hot weather (95+ degrees F), it runs warmer than otherwise - A/C or not. But I've never had the needle actually enter the "H" zone, so I don't worry about it. The story might be different with a high-performance engine, and someday I might have to deal with that.

In fact, right now I'm dealing with condenser placement in my MG Magnette saloon and that does pose a problem. On these cars, the bonnet lock platform crosses in front of the radiator less than 1/4" from the core. Here the problem with a lower mounting is extreme vulnerability. But hey, I'm on the wrong board for this problem.

Cheers,
Allen
Allen Bachelder

Allen - Wrong board, maybe, but many of these issues cross boundaries. For example, what are you doing for an evaporator in the Magnette? Is there sufficient under-dash room for one of the available after-market units to be installed without surgery? If so, what model?

Issues of space management, sheet metal surgery, and so on are pretty universal - at least on a theoretical level. Many of us learn tidbits from the hot rod crowd, so we can sure as heck learn from your experiences on the Magnette. IMO.

Cheers!

R.
Rick Stevens

If you space the Magnette radiator back a little (you may need to swap to electric fan) that might enable you to get the condensor in front of the radiator.

I am interested that your fan is wired to come on with the aircon pump. On alot of modern cars it is wired to only come on if the aircon circuit pressure is not being kept below a certain level by the "natural" airflow.
David Witham

Rick,

Thanks for your open mind. You are absolutely right; I've learned a lot from the hot rod folks but I need to learn more.

There are several evaporators out there that will fit the Magnette, but I'm thinking of a boot-mounted unit such as Classic Auto Air shows on page 20 of their catalog. (Go to http://www.classicautoair.com/OrderCatalog.asp and download their pdf catalog.)

David,

Thanks for your suggestion. I wish that would work, but even with the mechanical fan removed there is no room for a puller electric fan behind the radiator - even in the original position.

I have tried a fan-forced condenser under the rear seat in a previous attempt and it did not work well enough. On the Magnette, I believe there is a solutiion but it involves removal of the bonnet lock platform and improvising a new bonnet lock. Since the grill and grill surround sheet metal is part of the Magnette bonnet, this can be done at the bottom of the grill. I'd rather find a less invasive solution if I can.

This installation will also benefit from solution of my original problem, so the two are related.

Thanks again!
Allen
Allen Bachelder

Thanks for your response, Allen, it is appreciated. I just thought that this person's condenser placement was interesting, altho I don't particularly like its vulnerability to road debris. I have tried a couple times to provide a list of links to sites I have found interesting on this subject, but each time, the submission has not gone through on this site. I hope this one does.

If anyone would like a copy of these links, contact me, and if you have some you think are worthwhile, try posting them, you may get luckier than I have been today.
Bob Muenchausen

Bob - I tried sending you an email but it bounced back. If you send me the link at this address (rick.stevens "at" us.army.mil) I will attempt to post the link here.

BTW, thanks for all of your input on these boards. You always seem to have just the right info.

R.
Rick Stevens

Thanks, Rick. I actually don't always, but I appreciate that folks think that the good outweighs the bad . . . er, not so well thought out stuff I sometimes post. Actually, anyone can find everything I have found doing a Google or other search for MGB Air Conditioning or variants thereof. Allen's source, Classic Auto Air, is one of the best.
Bob Muenchausen

Rick's comment about Bob reminded me to go revisit Muenchausen's Garage. http://www.cibolas7.net/4436.html. This is highly recommended reading. It was here that I learned how to build my own heater control valve; here that I learned about installing the Saturn alternator; and here that I was inspired to install headlight relays. I needed the relays because I went to higher amperage halogen headlights (' ever wonder what it would be like to drive you MGB at night with white light instead of brown?), I needed the extra amperage of the Saturn alternator because of the addition of A/C and the extra cooling fans that went with it.

Bob's site is extremely well written and insightful. And his thoughts on poverty are thoughtful and penetrating, to say the least. I hope I get to know this guy better someday.

Bob, thanks for your inspiration...

Allen
Allen Bachelder

And thanks to you, Allen, I too hope we cross paths one day as well. You have a wonderful collection of MGs, any one of which I envy. ;-)
Bob Muenchausen

And, I might add, Allen, equally good advice and discussions which have been most helpful to me as well. Helps to clear out the cobwebs in my own understanding and methods that have become too often as encrusted by "but I have always done it this way" to realize that better means and methods have evolved over the years.
Bob Muenchausen

Ahhh... Bob, thank you. But isn't that how us "old f*rts" stay young? If I have said one thing that helped you, I'm humbled and honored.

I suspect the boys at Abingdon often solved problems with "seat-of-your-pants" solutions and some of us who still prefer our Bs for modern daily travel still think like they did. And we arrive at simple, practical ways to make our cars more useful. Not because we're better, but because the superior design of the cars allowed them to last far longer than ever anticipated and the "next step" is left to us. That's where your solutions and your website come in.

It is the inherent quality of the cars themselves that makes them good daily drivers more than 25 years since they were built. Isn't that remarkable? I'm always happy for the "purists" who will preserve examples exactly as they came out of the factory. But I'm equally pleased that some of us will continue to show how these cars can be modestly adapted to serve well and pleasurably for so many decades after their manufacture.

Holiday Cheers,
Allen
Allen Bachelder

Hello,

Pardon my ignorance but is it possible to drive without the A/C belt? Apparently, mine was worn out was cutoff from the compressor. Right now the car was stuck in my office and thinking if I can still drive it back for around 20 miles and have it serviced.

My ride is classic MB W123 1980.

Appreciate any information you can provide.


Thanks in advance.


Dan
Dan

Dan, On most older cars yes. That said I'm not sure about your car, it's best to check that all components like water pump power steering pump and alternator are driven by a separate belt before driving it. Some newer cars have a single belt to drive everything.

Clifton
Clifton Gordon

This thread was discussed between 06/12/2006 and 19/12/2006

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