Relocating Low Side Port to Pressure Switch Location

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Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Mon Jan 16, 2017 9:54 pm

Due to modifications, I would really like to add a service port in a more accessible location of my vehicle.

The pressure switch area is a good spot.

Is adding a tee at this location a bad move? The idea would be to tee off the low side line, stick a charge port at the top, and reposition the pressure switch off the side of the tee.

My pressure switch uses a 3/8"x24 thread. Brass tees for brake lines are available in this size. All 3 ports female. It would take some adapters to get everything hooked up but it should work.

1. Is this a bad idea?
2. Would this seal? For example, the pressure switch has a green oring on it, I'm assuming all my adapters/nipples wouldn't. Is that an issue? Teflon tape? :mrgreen:
3. Would brass work?
4. Got any better ideas that don't involve removing a suction like and taking it somewhere?

Thanks fellas!
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Re: Relocating Low Side Port to Pressure Switch Location

Postby Tom Greenleaf » Tue Jan 17, 2017 10:01 am

Site's been slow, welcome back. What is this thing and what it the obstacle to leaving it alone?

Know some stuff: Threads for plumbing CAN be a seal #ed the same marked for plumbing not just thread counting and size. Brake parts seal not by threads at all but by the flare and line inside - know that. Teflon tape can be useful or a disaster depending on where used. Shards of it in wrong places can't clean out and doesn't dissolve in anything I know of.

First things first - what is this thing and is it at all possible to leave items where they are if it took a well thought out hole for access?

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Re: Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Tue Jan 17, 2017 9:45 pm

Thanks for the reply, Tom.

It's a 1992 Lexus SC300 that has been modified with a turbocharger. The turbine is right up against the low side port. I have installed a heat shield at this location to try to keep the port as cool as possible.

The issue with this is that A: I have to remove the shield to get to it and B) once the engine is hot, forget it. There's no getting your hands in there until it's cold again, hours later. It's VERY tight.

Obviously, this is no good for ac work when you need the system running to charge/diagnose/etc.

I did some ac work on this car 5.5 years ago thanks to you all, but now the AC stopped working due to low pressure switch cut out. I now have a new leak (or rather, a worsened old one). I'd like to start tearing into it again and it would be WAY easier if I could relocate this port to another location to facilitate the work.

Any ideas on a bolt-in way to get this done?

Thanks!
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Re: Relocating Low Side Port to Pressure Switch Location

Postby cornbinder89 » Tue Jan 17, 2017 10:30 pm

The 3/8's thread is a O ring fitting. So brake line fittings will not work. There are O ring to flare adaptors for trinary switches that have a Schrader valve in it. I suppose you could remove the valve and plumb it to a (flare) T fitting.
I wouldn't go that route. I would either replace one of the hose fittings with one that has a service port or splice a service port into one of the hose runs.
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Re: Relocating Low Side Port to Pressure Switch Location

Postby Tom Greenleaf » Wed Jan 18, 2017 11:53 am

I like Cornbinder's idea of a spliced in port for access and a LPCO switch. Now reading this very worried about the existing items staying in place at all with that much heat you probably could or have melted seals of any Schraders and can't keep a plastic cap on a port plus who knows for wires there either?

Would be some work just to find the right shop that could made up a perfect line all metal where it can get hot and insulate that area even more and place service items elsewhere. The right person with equipment with your existing connection at the ends should be able to do this probably cheaper than buying all the stuff to make up stuff yourself? Can't know as I never owned or bought stuff to do that,

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Re: Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Wed Jan 18, 2017 3:35 pm

Some good points have been brought up.

The line that passes thru this area is an aluminum line with nothing else on it besides the low side port. The port does indeed have a plastic cap on it and it hasn't melted. It's far enough away and protected with a heat shield so it's not that hot in this area to at least affect the cap. It will make a well done steak out of your hand however. The bigger issue is clearance. I can't even keep the R134 retro adapters on it.

The schrader in this port was leaking once, and I replaced it. Perhaps this schrader is the leak I have. I have yet to tear into it to verify. Who knows the quality of replacement schraders these days.

The LPCO switch is in a safer place and not of issue with heat. That's why I chose this area. However it seems a 3/8x24 w/ o-ring tee doesn't exist. Perhaps one can be custom made somewhere?

It looks like my only recourse here is to remove the suction line off of the compressor (the only one made of rubber) and have a shop rebuild it with a crimped service port section on it? Or choose a hard line and have something brazed?
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Re: Relocating Low Side Port to Pressure Switch Location

Postby cornbinder89 » Wed Jan 18, 2017 4:38 pm

Heat and leak seam like they might be connected.
A good shop with aluminum welding equipment and experience can install a 134a service port anywhere in a hard line. Someone with only a hose crimper is limited to a straight section of hose that they can cut and splice with a service valve fitting.
I am concerned about radiant heat getting into the 134a. any heat absorbed must be shed at the condenser or will be carried back to the evaporator. A/C is just a heat pump, the more heat you put into the system the less cooling there can be, unless you shed the heat somewhere. Insulating or re-locating lines to minimumise engine heat entering the A/C system is time well spent. Better to keep it out in the 1st place than to try and get rid of it after it has been absorbed into the system.
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Re: Relocating Low Side Port to Pressure Switch Location

Postby Tom Greenleaf » Wed Jan 18, 2017 4:50 pm

Heat and plastic? There's plastic used in that Schrader and you do need the cap - both can take a lot but I've measured exhaust manifolds at idle speeds run 450F which is pushing it - face it. Under load uphill into a headwind no doubt glowing which is about 750F I think?

Now understood no clearance for 134a retro fittings. There were some other cars there plain wasn't room in one case couldn't close hood over it so close and all OE except was R-12 OE like this and needed the adaptors. IDK - Just took it off and well marked it so no mistakes made for another.

You said you modified this but have to ask if this was available with what you did and just added it or custom job of some kind. If this was available originally I'd scope out the hose(s) that would be OE duplicates a maybe?

There's just one person in all of MA that no doubt makes up hose and fitting all custom for what you are doing - some hot rod or whatever so it can be done I just haven't gone there myself.

Question 4 you? You call this a pressure switch as in a LPCO and not going to look it up but thought all these were expansion valve set ups? Is this now a CCOT = Clutch Cycling Orifice Tube design by YOU? If dependent on that switch for proper on and off time lots will matter. If just an emergency shut down switch I'm not sure?

*****************************************************
Other and chat: Just one car by chance, a '78 OE Corvette had a low pressure hose and accumulator so close to exhaust heat and all original it baked that line and only car even with the small cab area couldn't make it super cool inside just adequate. Fine for that as the whole car A/C wasn't the point. So do shield it as you said you did and look to make that even better if possible.

So if having trouble for this hose, switch and port up to whole hose made up check around your area for custom car work then on to where someone gets help locally to make up what you need or give it a shot and do it.

Aluminum welding called "Heliarching" (sp?) is its own skill. Tools for crimping hose to fittings and line takes tools and measure twice so it's right the first time or start over now may have troubles finding a specific manifold fitting for compressor - I just can't know how hard to find.

Check up top for tools if still anything there how much a hose making kit cost. Call but I don't think site's original store is open at all?

Sorry about all this. This forum area is so slow it's just a couple of us until owner or who pays the bills decides to shut it off for archives only is my guess.

Click up top as that should be the current owner's site and may take you away from this one just to look and maybe check it out at that site. I was there but no time recently nor know anyone there unless user names is same as here.

Good luck. I do check in a couple times a day to clean up spammers before anyone sees total garbage get rid of those,

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Re: Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Wed Jan 18, 2017 5:53 pm

Yes, heat management is and always was a concern of mine. To further explain, the turbocharger was ceramic coated and THEN wrapped in a turbo heat blanket. Add to this the aforementioned heat shield installed over the ac line and the ABS module that are next to each other. Things are pretty well protected.

As for the system taking heat, it used to blow 38 degrees F in Miami after some work I did on the system with the help of this very forum 5.5 years ago. It had a leak at the expansion valve, so I went ahead and replaced that, the orings, the dryer, schrader and some other orings and put it back together. It was great until now. Tho you bring up good points, I can further insulate the lines with some heat wrap.

Tom, by pressure switch I mean the factory switch which I suppose is to protect the compressor. It is indeed an expansion valve setup, as factory. I know it's working because the compressor clutch wouldn't engage recently due to low refrigerant charge. It did run when I jumped it. It also cuts out at a high psi as well.

The turbo setup is a totally custom modification so there are no factory available lines with an alternate low port location.

I know locally there are machine shops that will make you custom ac hoses if you bring them your old ones to use as templates/harvest ends. Perhaps if I bring them my rubber hose suction line they could crimp a port in the center? I think this would be the easiest way to do this.

OR, take them the hard line with the issue, have them remove/weld up the existing port (to curb any heat related schrader failures) and weld in a new port in a better place. Problem with this is that hard line is LONG and snakes thru many places... would be a huge undertaking to remove/install and not break.

This ebay listing shows the line with the original port in it. The one I want to change. It points straight into the engine bay from its frame rail location on the way back to the firewall. I'll assume this link is okay as I'm not buying anything, it's just to show what my lines look like.

http://www.ebay.com/itm/Lexus-TOYOTA-OE ... F4&vxp=mtr

And this is how the lines are routed in the car. The low port is on the hard line near where the EPR is labeled.

Image

Thanks, fellas. I will ask around locally to see what I can have done.
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Re: Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Wed Jan 18, 2017 6:03 pm

Looking at the very pics I just posted, I just realized the pressure switch is on the liquid line going into the evaporator.

I suppose that doesn't make it very suitable for a Low Side port now does it? :mrgreen:

Narrows the choices. One day I'll learn to look at things proper. One day. :lol:
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Re: Relocating Low Side Port to Pressure Switch Location

Postby Tom Greenleaf » Wed Jan 18, 2017 6:35 pm

Pressure switch on HIGH side is either a Lexus design or when if car was "retro-fitted" done to legal spec as a High Pressure cut out the idea is stop compressing if too high before any pressure relief valve allows refrigerant to escape prior to 134a wasn't required and many kits to convert systems just ignored that.

Hey - It's a Lexus so might have been early for a coming requirement or in use to monitor the pressure which also converts to what temperature the line is for reason they wanted. It's there and worked so use it and keep it working.

Noted that if you lived in and had work done or got help/parts in Miami there would be lots more attention to A/C and choices than in Massachusetts that gets hotter but for an hour not all day!

Also due to use of rock salts for ice and snow any vehicle used and driven in that would now be long rusted out beyond any hope of keeping it. Stuff is here just put away for the season (like my own) and fine the rest of the year is a few years older than this still kicking, OE A/C, R-12 make a polar bear scream for mercy!

Smile but not now it's chilly about now 'round here for a bit longer,

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Re: Relocating Low Side Port to Pressure Switch Location

Postby cornbinder89 » Wed Jan 18, 2017 7:53 pm

In the E bay listing, the line with the blue cap port is the low pressure line, the small line is the high pressure liquid line. On the ebay line someone has already put a 134a adaptor on the port.
It would seam possible to find another spot to have a 134a port welded on.
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Re: Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Thu Feb 02, 2017 3:50 pm

I found this splice kit, which uses a compression tee with green orings to seal.

I wonder if this is any good? It uses green o-rings so it should be a good as an oem seal, no?

I could also perhaps tap a threaded GM low port on my compressor block? Meh.

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Re: Relocating Low Side Port to Pressure Switch Location

Postby Tom Greenleaf » Thu Feb 02, 2017 4:36 pm

I'm sufficiently confused - sorry. Trying to figure what that thing would be useful for without ability to hook up a low line to a high pressure line if you weren't paying attention as a generic something?

Where's this compression fitting with "green" seals now all should be 134a compatible??

Tap what? Compressor block you mean drill and tap a hole for a fitting or what. Remember those should be a plumber's threaded hole by rights should self seal but bet it wouldn't seal vapor under pressure without some tricks I really don't think I'd trust?

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Re: Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Thu Feb 02, 2017 4:54 pm

Tom:

The above tee would be to relocate my low side service port to another area more accessible on a section of hard line. Using this tee would allow me to not have to remove that very large section of hard line. It could be cut and installed in place. It is a compression style tee, but it uses green orings for sealing. They are not shown in the pic as it is shown assembled.

Or...

For the compressor block option, I have sufficient clearance here to install a threaded and oring style service port like the one shown below. It is 13mm x 1.0 Pitch Thread.

Image

Not sure how much meat is on the back of this block, would have to verify:

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Re: Relocating Low Side Port to Pressure Switch Location

Postby cornbinder89 » Thu Feb 02, 2017 5:35 pm

Compression fittings work OK on steel lines, less well on aluminum. Over time they tend to leak. The "olive" is compressed onto the line by the tightening of the nut, over time and vibration, it tends to compress the line and loosen the fit. After a while, no amount of re tightening will cure the leak. This happens faster on the softer aluminum than it does on steel line.
Duetz air cooled diesels were famous for their oil coolers leaking, they were a heavy wall (much heavier than AC line) tube and fitted to the block with a compression fitting. It happened much quicker on the engine than it would off, like on a A/C line, but the same forces are at work. Oil is much thicker than 134a, and a little oil leak is tolerable, while not so much for A/C.
I guess what I'm saying is for the short term if that's the best option you have, than go for it, but long term I think it will be a source of leaks.
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Re: Relocating Low Side Port to Pressure Switch Location

Postby cornbinder89 » Thu Feb 02, 2017 5:41 pm

To "drill and tap" the block fitting you also need to counterbore the hole to accept the o ring, sometimes a simple bevel will work well enough, but the o ring must be compressed without extruding out under the fitting or getting cut, or be loose and not compressed.
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Re: Relocating Low Side Port to Pressure Switch Location

Postby CleanSC » Thu Feb 02, 2017 5:42 pm

Fair enough! Great feedback, this is why I ask here first.

Thanks for the confirmation.
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Re: Relocating Low Side Port to Pressure Switch Location

Postby Tom Greenleaf » Thu Feb 02, 2017 5:43 pm

Sorry again if I'm messing you up - I don't do this and never had troubles like you have.

In those pics the top port threads are not Plumbing threaded so rely ion that seal. At a glance I just don't like that thing - just me.

Lower pic of hose you want to drill and tap hole for a port? Never did that so can't say from experience what troubles might crop up.

Think I'd rather have a port put in the metal line aluminum welded in or to a proper threaded nut onto the line?

I'm just worried that drilling and tapping into the block part to compressor could mess up how it seals to compressor? Not sure but if you try that be sure you can get another hose. Oh boy - how you would hold that to drill it would even worry me. Guess I'm plain worried this isn't going to absolutely work out and fear that.

Do know that slow leaks not caught are #1 to ruin a system that somehow never default to shut down on time and burn out compressors that stay running too long without oil carried or enough of it.

I hear it in my own still R-12 all OE car only when outside the car like a Lexus no doubt it's so sound proof there's little to no awareness of noises under the hood so well insulated for noise alone on purpose! Different game as I've owned it so long and it's my own can catch it on time and have for decades! It's closing in on 30 years old still all OE! Granted not stressed that much in New England either,

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Re: Relocating Low Side Port to Pressure Switch Location

Postby cornbinder89 » Thu Feb 02, 2017 7:37 pm

Another thought, If you have a long run of tube that is easy to access, rather than compression you can cut and flare either SAE or AN flare. You still need to fit a service fitting in there somehow. I have use NPT fittings on one A/C with luck, but assembled with loctite on the threads. It was at a drier that had NPT to quick-connect fittings and the quick connect failed.
It would be a pile of fittings, but you go from tube to flare to pipe T back to flare to tube. Then go to 1/4 or 1/8 pipe on the T to 1/4" flare to 134a service fitting. The more adaptors the more chances for leaks, so I really couldn't recommend going this way.
I think when all is said and done, the thing to do is to pull the line and PAY someone to weld a fitting where you need it. Only one place to leak that way, and much less likely to do so.
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