View Full Version : TR6 TR6 A/C question(s)

06-23-2008, 02:26 PM
My 74 TR6 had A/C in it when I got it years ago, but I've never seen it work. If I hot wire the a/c clutch, the compressor runs and sounds normal but it doesn't cool and nothing appears in the site glass. It's getting warm here and I'd like to be able to use the car during the day when the sun is out (with the top up and A/C on). I'm thinking of changing out the compressor with something more efficient and less power robbing and going to the new freon. Does anyone have any suggestions or considerations?

I've already installed an over-rated alternator and extra cooling fan, as well as repalced the worn door seals and sealed the transmission tunnel leaks, and have a decent top, etc.

The latest Moss catalog shows a unit for MGBs, but no mention of retrofiting a TR6 -and nothing on their web site.

06-23-2008, 02:29 PM
Something you also might want to do is add a relay that automatically turns on the fans when the A/C is on. That is the way the 7's and 8's work

06-23-2008, 02:34 PM
It may just need a good old fashioned charge of refrigerant to be OK. Add a dye if possible, in the event there are any leaks, to make them easier to find.

06-23-2008, 02:47 PM
Knucklehead, I was also going to suggest checking the charge condition. My 6 still has the dealer installed A/C but I haven't bothered with it since the P.O. said it had a slow leak somewhere under the dash. I could convert it to R134 and try it out this summer...but I settle with letting the day cool off and lettin' the top down. I removed the compressor belt a few years ago 'till I figure out what to do.

06-23-2008, 05:51 PM
Unfortunately, it's not that simple. The R134A stuff is actually less efficient than the old R12; and will cause all sorts of problems with your old equipment. At the very least, you should remove all the oil and flush everything, then replace with the proper synthetic oil.

It's also recommended that you replace all the soft lines with modern barrier ones. R134 will penetrate the old material and leak right through the lines. Shouldn't be too hard to find a shop that can install new lines to your old fittings, but I ordered all new ones from

Of course, you'll need a vacuum pump to evacuate the system low enough to remove any moisture inside. I'm told that R134a is more sensitive, because it will combine with water to form acid that corrodes the system. But even the old R12 systems didn't like moisture in them.

Unless I'm mistaken, the TR6 also runs the condensor fans all the time (when AC is selected), regardless of whether the compressor clutch is engaged at the moment or not. The Stags definitely work that way.

06-23-2008, 06:03 PM
Refrigeration units in CARS?!?!

wow. What's next... computers?

06-23-2008, 06:20 PM
If you have got one and want to rebuild it, good. The idea of checking your car out for exhaust leaks is valid. I have a brand new exhaust system in my car, albeit somewhat a custom system, and I really don't trust it to enclose the car for AC. I have found that the zippered rear window on the soft top works really well for keeping fresh air flowing through the cabin. I can understand a car with the factory hardtop wanting to air-condition for the hot months, just check out the exhaust coming in through the firewall, floors, etc.

06-23-2008, 07:51 PM
This may be of interest to someone. Hot Rod Air does not make a kit to add A/C, but they have this bracket, which may work for someone looking to upgrade to a newer compressor.
https://www.hotrodair.com/index.cfm/page/...=prod/prd88.htm (https://www.hotrodair.com/index.cfm/page/ptype=product/product_id=88/category_id=56/home_id=2/mode=prod/prd88.htm)

06-24-2008, 12:44 AM
The A/C units I have seen have "cut out " switches that sense low pressure and high pressure. When the pressure is too low or too high, the A/C clutch will not activate. I don't recall seeing any brand compressors other than the York brand used. There were a lot of thse compressors made and used on many different cars. The system is pretty simple and should not require much effort to get it working. The more difficult area to check is the valve and coil under the dash. If you get the system leak free, there is nothing wrong with the standard, dealer installed A/C. That cool air is hard to beat in the hot, humid south. If I changed my A/C out, it would be for a supercharger, there is just too little room in there for both.

06-24-2008, 01:29 AM
Couple of relevant links :
(For some reason, Terry Geiger's TR6 AC article has been taken down, but much of it is still on the WayBack Machine (https://web.archive.org/web/20031010165818/https://www.shoalsbritishcars.org/tr6ac.htm). I've got the whole thing, let me know if you'd like a copy.)


Oh yeah, my apologies. It appears that at least one version of the TR6 AC did have a pressure control, to only run the condensor fan when condensor temperature (as indicated by pressure) was high.

06-24-2008, 10:41 AM
Okay, To avoid throwing lots of money at this car. I recommend taking it to a local, well recommended ac repair shop. Or garage that does lots of ac repairs.

Why??? If you know nothing about the system on the car you could be throwing dollar after dollar(kinda like Tinster) at one item after another trying to get the ac working and reliable.

The car is over 30 years old. That means the flexible hoses are also over 30 years old, so strooooong probability that they are worn, leaking, along with the sealing o-rings. But it is so old it could have just used sealing washers. Major components are going to be compressor, receiver dryer, condensor and evaporator with expansion valve. The receiver dryer should be replaced and the others checked. Possible just one of the pressure control switches or expansion valve is bad.

But rather than trying this part, then that part, and having your frustration build; take it to a pro for a complete and thorough inspection....

06-24-2008, 05:31 PM
:iagree: That would be the most desirable route.

However... a simpleton's thought:

Due to the age of ALL the components could it not be possible to fit a "beef-roll" compressor (swash-plate type), R&R the receiver/dryer, hoses and expansion valve to accomodate 134a and have less load on the engine?

The cost of converting it would seem to be close to doing the OEM refurb and *benefit* with available refrigerant and a less demanding compressor. That York unit is positively caveman tech.

<span style="font-style: italic">Disclaimer: I harbor NO prejudice toward ancestral predecessors. Merely an allegorical allusion to current media advertising whims.</span>

06-24-2008, 06:39 PM
I was thinking that in the long run, it would be better and cheaper to replace everything with updated equipment (it's already exceeded it's expected lifetime). Having it charged would lead to finding the biggest leak, followed by another charge and then repairing the next weakest link... until the cost of recharging exceeded the cost of a new system. IMO.

I started by replacing the original cooling fan that looked more like a refrigerator compressor cooling fan, than one found in a normal cooling system.

I'm thinking of contacting www.vintageair.com/index.asp (https://www.vintageair.com/index.asp) and see what it'll cost for a complete upgrade.

06-24-2008, 06:49 PM
Having it charged would lead to finding the biggest leak,. I believe it's actually illegal now to put refrigerant (even 134a) into a system that is known to be leaking. You should definitely fill first with air or nitrogen, and check if it holds pressure.

Don't know if anyone cares, but here's an interesting link I found while discussing this issue off-list :

R-406A is supposed to be a "drop-in" replacement for R-12. Haven't tried it myself, but I trust it's inventor (an old Purdue chum).

There's also some interesting info at