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MG MGB Technical - A/C questions

I would like to put A/C in my 65 roadster. What would be the best compressor and other components? I am thinking of using an old 1977-1980 MGB A/C set of controls.
Frank Baker

If you use the evaporator and condenser out of an older setup, I would recommend using a Sanden 507 compressor. They are commonly available, and aren't near the drain on your engine as the old Yorks and Mini Yorks. A local shop can make your hoses, but they will need to know the types of fitting on your condenser and evaporator as well as the length.
Ace Brandt

Frank, Ace is exactly right. If you haven't done this before, check out Vintage Air's website http://www.vintageair.com . In their downloads section they have a LOT of good information from physical design to electrical diagrams.

As long as you have the passenger compartment controls, you're good to go. It would be best if you also have the under-dash evaporator as well, since the smallest model sold by Vintage Air is really too large for a B. If not, let me know - I found one that's a good match but I don't have the contact info at my fingertips right now. I'll be glad to look it up for you if needed.

R.
Rick Stevens

You might also check out these guys, http://www.classicautoair.com/vintage_air.asp , as they have a somewhat different product line than Vintage Air.
Bob Muenchausen

I too would love to put air in my 67BGT during the restoration. My roadster gives me all the top down originality I want and I want to drive this GT when it is HOT outside. I have been wondering if any of the aftermarket companies have a B sized application easy enough to make work with a 67 wiring harness and electrical system.....upgraded to an alternator of course. Anybody done this? What all was involved? Do the aftermarket folks give you everything you need except pully and belts etc? Where would the evap go? I would guess the old 3 blade fan and early radiator combo could not carry the load. I would certainly add the A/C even with reduced horsepower if the system was effective and somewhat simple.
Ralph

Bob - I actually think Classic Auto Air was the place I was thinking of. I need to fiddle through some catalogs to be sure, but that's what I have in the back of my head. If so, they have an under-dash evaporator that's almost a dead ringer for the "original" aftermarket units that were installed.

Ralph - This isn't really all that difficult. You need to be ready to make some mods and some compromises, but technically it's no great shakes. The fitment is more of an issue than the required technical expertise. The aftermarket companies can help, but they do NOT have a B-specific turnkey system. You'll need to do your homework first, and be ready to tell them "No, I don't need widget A, I need widget B." They'll listen and be boo-coo helpful, and will work within your knowledge level. Just make sure that level is high. ;)

One thing that helps is to think of this as a hot-rod installation instead of an LBC one. When you're talking to their techncial folks, or to a local a/c shop for that matter, they're used to dealing in those terms and are a lot less likely to feel intimidated by you and your project.

As for the electrical system, upgrading to a (high-output) alternator is pretty well mandatory. The individual wiring can be/should be its own sub-harness and isn't difficult to fabricate from Napa 10 gauge wire. The only wiring is to the switch and thermostat; blower motor relays; cooling fan relays and thermostat; trinary safety switch; and compressor clutch. Sounds like a lot, but it can easily be self-contained.

The 3-blade fan by itself will likely need some help, but this is easy enough - you'll be mounting the condensor forward of the radiator anyway, most likely, and should mount a 10" or 12" (if it'll fit) electric pusher fan in front of that. This will likely have dual controls - coolant temp and a/c system pressure (the trinary safety switch).

As for horsepower loss, that will be minimal. With modern compressors - the Sanden unit recommended by Ace being the best choice - you see very little pull on the engine. The biggest concession there will likely be setting your idle speed up a tad so that the engine doesn't sputter when the a/c kicks in at a light or in traffic. On the road it'll be almost unnoticeable. (In fact, studies have shown that an open window is a lot less efficient than an operating a/c system just because of the extra drag caused by trying to haul all that extra air in the back of the car.)

R.
Rick Stevens

I've done this - with a mix of Classic Auto Air components and an original evaporator. The usual bracket design involves running the A/C compresor and the water pump on one belt with the alternator running off the compressor (Sanden with a dual pulley arrangenent) on a separate belt. This is not a good solution as enough belt tension to keep the compressor turning will tear up a water pump in just a few thousand miles. This is the arrangement I have from the past two summers and now I need to modify it so the belt off the harmonic balancer runs only the compressor (as tight as it needs to be!), and the remaining sheave on the compressor then can drive the belt to the water pump and alternator at whatever tension is appropriate.

Others have done this; unless they come forward, we have to re-invent the wheel. Outside of that, I have tracings from the brackets for my MGB that were provided by Classic Auto Air - with permission to copy them as I bought the last set they had and they didn't intend to make any more. Anybody interested, e-mail me off-list.

A/C is just another doo-dad to hang on your car. You should understand a little about how it works, but rocket science it ain't. New components can be mixed with old - as in evaporators. But don't mess with old compressors. There is no need to; they aren't very efficient; they take up way too much space in your engine bay; and they're expensive to source and overhaul. Why? Modern Sandens are inexpensive, efficient, compact... Why not? Even old evaporators can be made to work with R134 (don't even CONSIDER R12!!!). If necessary, Classic Auto Air will rebuild your old evaporator. Beyond that, you need a condenser, a dryer and some hoses.

I used a Saturn/Delco alternator with about 105 amps, two Hayden electric pusher fans, and lots of relays. The learning curve is complrex but not steep. If I can do it, so can you!

FWIW,
Allen
Allen Bachelder

BTW, Allen's drawings and write-up do a good job of filling in the blanks as you go. Solid, valuable info....

R.
Rick Stevens

"(In fact, studies have shown that an open window is a lot less efficient than an operating a/c system just because of the extra drag caused by trying to haul all that extra air in the back of the car.)"

Rick, you're a hoot! Hauling extra air around, indeed! I about fell out of my chair! Everyone knows cold air is denser and therefore there's more of it to haul around in the A/C car. In fact, Mythbusters proved it in a test where they ran an old Oldsmobile around a track doing a comparison, and it went farther with the windows down and the A/C off. They weren't running it at freeway speeds though and I suspect the drag has something to do with it at higher speed, maybe even offsetting the weight of the colder air at some point. Could be that the high speed wind entering the car compresses the air so there's actually more of it in the car. The driver wouldn't notice because since he's breathing the same air he'd be equalized.

Jim
Jim Blackwood

Rick

If you can identify the source and model of the evaporator please post. Definitely something that I am interested in for a future install.

Thanks

Larry
Larry Hallanger

I gotta admit, Jim, I was taking a bit of "poetic license" with the phrasing. ;) The operative word there is, as you said, "drag".

I actually missed that Mythbusters episode - I love those guys. They had a show recently where they went back and redid some of their experiments where viewers had spanked them for "doing it wrong". They 'fessed up to a couple of errors, too - but they still proved that a cargo net on a pick-em-up truck is more efficient than a tailgate in any configuration.

Larry - I'll look for that info this evening.

R.
Rick Stevens

Bob M. nailed it: Classic Auto Air is the place I was thinking of. They have a "4-port Evaporator Kit" that is almost a clone of the aftermarket units placed into the B's. Their home page is noted above, but this link gets you right to the relevant page on their online catalog: http://www.classicautoair.com/Catalog/Univ%20Cat%20-%20Page%2016.pdf . It's part # 1-1011.

BTW, you may well find yourself mixing-and-matching components from different vendors. For example, Vintage Air sells a set of under-dash vents that I like because they're pretty close in appearance to the pair of aftermarket B vents I have. Hot Rod Air has a condensor that may be a better fit than some others (if I decide not to reuse the unit I have).

It is completely realistic to think you can get a complete a/c system into your car for a reasonable price that will look like it belongs. To repeat
Allen's comment: It ain't rocket science. If I can do it, you certainly can.

R.
Rick Stevens

Great info guys....thanks for the links and details. Seems quite possible and the experience of others is always the best starting point for reference.
Ralph

Great information! I would like to see if I get some clarification of a couple of things.

I understand a Sanden 507 compressor is the “ticket”.

I bought a bunch of parts off EBay. I think (the parts are not here yet, but…) I have the vents, controls, bracket and evaporator with the box. I would like to know the type of car that uses the Sanden 507 compressor and I will go rape a car of all the components (Accumulator, Schrader valve, compressor, hoses and condenser) and replace the original components with modern ones, measure the hoses and have new hoses made up and then take the whole installed system down to my locate A/C guy who will evacuate it, check for leaks and fill it up.

Is this a reasonable plan??
Frank Baker

It is a good idea, within reason, but the hose measurements may be irrelevant from one car to another. You're getting the most difficult-to-find parts so that's a good start.

New parts you'll definitely need are hoses and the drier. A drier is cheap, and a "clean" one is important for the long-term health of the system. I would also get a new safety switch, also because a new one is cheap insurance. On the other hand, if you're getting a working evaporator you may not need a new schrader valve.

As for the condensor, getting a good fit is important, but it doesn't have to fit as neatly as the radiator does simply because it's an aftermarket addition. If you have a good set of measurements you should easily find one that will slide in okay.

This particular Sanden compressor is pretty much universal in mid-size and small cars right now, and has been for some time. You can just about do a "pin the tail on the donkey" act and snag one of these at a junk yard. If it doesn't work you're not out that much money - you can go back quite a few times before you spend $300 or whatever it is.

Sounds like a good way to save a few hundred dollars.

R.
Rick Stevens

Forgot to add: Don't forget cooling system upgrades.

R.
Rick Stevens

OK, What "cooling system upgrades"???? I think I missed the point here
Frank Baker

How much do you think the total cost fo AC is?
D Enghauser

Frank - You'll likely find you need to add an extra electric cooling fan, along with its associated thermostat and wiring. It's not costly, and not all installations need it. Even if you don't actually need an extra fan - that is, your cooling system is just fine with the extra load - it's not expensive and not particularly difficult to install.

What it offers in addition to extra engine cooling capacity is that when used with a trinary switch it can be set to come on *before* the a/c system's normal operating pressure causes the compressor to cycle off for a bit. This makes for more consistent cold air delivery, particularly on really hot days or in stop-and-go driving.

As for cost - I like Frank's approach: Getting "pre-owned" parts from a salvage yard, eBay, craigslist, etc., where possible. Buying an all-new system can run from $700 to $1200 - more or less. This is a ***COMPLETE*** WAG (wild-assed guess) because there are no turnkey systems for the B. As an interesting side note, Moss UK used to sell a kit for about $2,000 (USD) but it's no longer on their website.

The best advice there is to check out the vendors' sites and catalogs - they are chock full of good info, technical and monetary.

R.
Rick Stevens

This thread was discussed between 25/01/2007 and 27/01/2007

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