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-   -   '70 Nova LSX swap LY6/TH400 (http://www.offroadfabnet.com/forums/showthread.php?t=8160)

TheBandit 09-26-2018 04:11 PM

Those pesky thignamabobbers... they always fail in the worst way, sending whatchamacallit through the hooziwhatsy. The only system more difficult to repair is a turbo encabulator.

entropy 09-26-2018 08:38 PM

...Ahhh... but the TE is rather simple, once you get the shell off.
The AC can be perfect and still not work or pukeitsgutsout for no known reason...

mdslngr77 09-27-2018 12:17 PM

old school systems that used the adjustable regulator were so much nicer, you can at least tune them. Newer fixed orifice or TXV is basically bolt in and hope for the best. Automotive doesn't have the adjustment that HVAC has so superheat and subcooling calculations don't come into play as much

TheBandit 09-27-2018 03:12 PM

Just a clarification, my system does have a TXV. The TXV regulates the refrigerant flow into the evaporator while trying to maintain a fixed superheat. The POA is really setting the minimum temperature (via pressure) in the evaporator while the TXV is making sure the right amount of refrigerant is getting in to carry off the heat from cabin air and ensure the refrigerant is superheated enough to prevent slugging the compressor. If the refrigerant is superheated too much (indicating their isn't enough refrigerant going through to absorb all the heat from the cabin air) the TXV opens to allow more refrigerant to the evaporator. The POA then opens slightly to keep the pressure in the evaporator from climbing (which would increase the evaporator temperature) and allow that extra flow through - the pressure stays as low as it can be to keep the temperature minimized near the freezing point of water. If there is too much refrigerant flowing through the evaporator, the refrigerant may not all be evaporated which will lead to low or no superheat. In this case the TXV will close down to reduce refrigerant flow. Consequently the POA will also close down to keep the pressure in the evaporator up at that lower flow rate. It's quite an artful balancing act.

TheBandit 10-01-2018 12:54 PM

Yesterday I installed the POA suction valve and the new TXV with fresh o-rings throughout. The new TXV is not application-specific so the capillary tube for the sensing bulb and the external equalizer line are much longer than they need to be. This results in some ugly coiled-up tubing, but at least the TXV is calibrated properly for R134a. I clamped the sensing bulb on top of the evaporator outlet using the original clamps.




The sensing bulb must be insulated from the engine compartment otherwise it will react to fluctuating engine compartment temperatures and radiator wash instead of the evaporator. This requires the use of an insulation tape commonly referred to as Prestite. I ordered a foot of tape from Nostalgic Auto Air when I purchased a few other components. I was a bit confused because the tape has a white wax-paper backing on one side that removes easily and a clear cellophane cover on the other side that looks like it should be removed, but was terribly difficult to get off. I confirmed today the clear covering is meant to stay just on to keep it clean.


Tonight I'll wrap the bulb and continue working to seal up the system. I have yet to install o-rings at the compressor and condenser and I also need to add compressor oil. Then I can work on wiring. My plan is to use a relay so the radiator fan is always on high when the compressor is on. Power to both the relay and the compressor clutch will be provided through the ambient temperature switch and hi/lo switch installed in the drier. The ambient temp switch will prevent compressor activation under 37F ambient tempt. The hi/lo switch will shut off the compressor for excess/unsafe pressure or undercharge.

entropy 10-01-2018 01:13 PM

In my opinion your AC layout looks a sh!tload better then most!

To get nice coils in soft tube you can wrap the tube around an appropriate size tin-can (OR....).
Wrap it as tight as you can, it will spring back allowing can retrieval.
A pain in the arss to be sure & may not be worth the effort...


TheBandit 10-01-2018 01:25 PM

Thanks e and thanks for the tip. These were already coiled when I got the TXV and they have a few weird kinks. I will try to clean them up a bit and then I plan to put the same braided covering on them that I used for my wiring.

CarterKraft 10-02-2018 01:34 PM

Pretty awesome you are able to re-implement this stuff for r134a.

I have to work on this stuff as part of my profession and I'll just tell you that I think you are much more educated in it then I have become in 20+ years of doing it.

TheBandit 10-03-2018 12:02 PM


Originally Posted by CarterKraft (Post 144830)
I have to work on this stuff as part of my profession and I'll just tell you that I think you are much more educated in it then I have become in 20+ years of doing it.

Your 20+ years experience has probably solved a lot more problems than my 5+ years of education! :beer:

When I jumped into mechanical engineering, I did not expect so much of the curriculum to be thermodynamics, fluid mechanics and heat transfer. It turns out some of that has been very useful, especially in this case. I am building my understanding of air conditioning armed with a few years of coursework, an insatiable curiosity, and a wealth of information available online. I am still more of a theorist than a practitioner though - this is the first AC system I've worked on so guaranteed I will make mistakes that a even an entry-level technician would laugh about. And I probably have at least a few flaws in my understanding of how it works. But I have no problem geeking out about it!

TheBandit 10-09-2018 12:27 PM

With the days getting shorter, I've been doing a lot more night driving in the Nova. I learned my original tail lights were very unreliable. The passenger tail light would not ground properly through the housing and would periodically just stop working altogether. Cleaning the contact and jiggling the socket could sometimes get it working again but before long it would be out. The driver tail light had it's own issue - sometimes the brake/signal would not work at all even though the bulb was fine. That means sometimes I had no brake lights at all and just one of two running lights!

My path home involves stopping and turning from 50mph traffic without a dedicated turn lane. Recently every time I made that turn I was bracing for the car behind to plow right through me, not knowing if my tail lights had stopped working during the drive. I came home the other night with that top of mind and sure enough when I checked neither of my tail lights were working. That was the last straw! I ordered a pair of Easy Performance LED panels right away.

Here is a side-by-side photo of the running lights with the passenger side LED panel installed vs the driver's side original.


As you can see above the Easy Performance LED panels illuminate the ENTIRE tail light lens while the factory bulbs only light up about 1/3 of the lens. The panels use red LEDs so even the clear reverse lamp lens can illuminate red. That is the main reason I chose these panels - maximum*visibility. Now on to the installation....

Easy Performance LED Panel Installation

The first step to install was removing and disassembling the tail lights. To get them out I had to loosen all the bumper bolts and then there are just a few nuts holding them on from inside the trunk. The lenses are attached by 4 shoulder screws and they can stick to the gasket inside the housing, so I pushed my thumb through the bulb opening to pop them out from behind.


The factory housings have a couple of bent-up tabs that I assume are used to mask light from the tail and backup lamps. These protrude and would interfere with a flat LED panel so they need to be bent down using pliers and a hammer (with the housing backed by wood).



There is also a piece of plastic protruding from the reverse lens that needs to be clipped and filed flat.

The lights wire to the factory bulb sockets (more on that later), but they have one extra wire that's used to get ign+ power for sequential operation. That wire needs a pass through, so the housing can be drilled near the reverse bulb socket opening and a grommet installed.

A this point the inside of the housing needs to be cleaned well so the LED panel can adhere using double sided adhesive. Rubbing alcohol works well followed by a little dry time to keep the rubbing alcohol residue from affecting the adhesive. This is also a good time to clean the inside of the tail light lens with some dish soap and a brush. Now the wires can be passed through their respective openings.

Next the LED panel can be roughly positioned along one edge against the small gasket-retaining tabs in the housing. With the panel tilted up you can see where each of the 3 double sided adhesive strips are located to attach the panel. The backing can now be peeled off and the LED panel pressed into place in each of those locations.

Now it's just a matter of reassembling the tail light and putting it back in the car.

After finishing the installation I found I still had a few problems with the original tail light sockets. The spring contacts inside the sockets were too short to make reliable contact with the new bulb sockets and the entire socket was still pretty corroded. I was able to correct that by cleaning all the contact surfaces with a Dremel and then using small needle nose pliers to pull out the spring contacts until they made a stronger connection. This step probably would have fixed the problem I was having with my original passenger brake/signal light. But it would not have fixed the ground issue. One benefit of the new LED panels is they use both the reverse socket and tail socket ground connections which provides redundancy.

I should note that the use of bulb sockets on these panels is entirely for convenience of installation. There is no reason you couldn't clip the wires and connect them directly. I'm sure that would provide more reliable connection and I might consider going that route if I have more problems with these sockets in the future.

Last 2018 Santa Paula Cruise Night

With the new LEDs out back, I set off to the last Santa Paula cruise night of 2018. I knew it would get dark before I left for the 30min drive home and it was great knowing the car would be extra visible now. Peace of mind!

entropy 10-09-2018 01:32 PM


Had to go look to see if my old Ford Truck might be listed... it is too new :laughing1:


TheBandit 10-17-2018 01:34 PM

I don't think you fit their target market!

I managed to wrap the TXV sensing bulb with a layer of insulation tape (aka cork tape or prestite tape).



Then I installed o-rings throughout the system and added compressor oil. I decided to use PAG46 because that is what's called for by the compressor. I added the oil through the suction port and rotated the compressor by hand to draw it into the system. The oil I'm using is NAPA Premium which is a house-labelled bottle of Dow chemical Ucon 244.


Now that the system is completely sealed up, I can turn my attention to the wiring. For the compressor, my strategy is to use the original, non-cycling control method which will run the compressor any time the switch on the dash is set to an ac-demanding mode (Max, Norm, Defrost, etc). Cycling systems turn the clutch on and off to prevent low evaporator pressures from freezing up the system, but with this system the POA valve ensures the evaporator pressure is always high enough to prevent freeze-up. The TXV and POA valve regulate the flow of refrigerant so the compressor can run continuously.

In addition to the compressor control strategy, I needed to decide how to operate the engine fan. I've decided to run the fan at high speed any time the AC compressor is running. This is a "brute force" method of operating the fan, but it will ensure the refrigerant is condensed and supercooled as much as possible and that the engine will get maximum cooling as well. The drawback is fan noise, electrical draw and wear will always be at their highest even in low cooling demand such as when running the defroster or lower blower speeds. An alternative strategy is to use a trinary switch which would only turn the engine fan on if the system reached a high enough operating pressure (indicating higher cooling demand). I decided against this because from what I could tell, all the trinary switches on the market had relatively high pressure thresholds, for example the Vintage Air trinary switch would not turn on the fan until 254psi. I'd be concerned at that point that I would not have adequate capacity and the evaporator pressure (and temperature) might start to climb.

Currently the ECM controls a 2 speed engine fan based on engine coolant temperature. To trigger the fan relay, it provides ground signals for high or low speed. I am using a Volvo fan relay and found it will run high speed as long as the high input is grounded, regardless of whether or not the low speed input is grounded. My goal is for the fan control to operate normally with ECM control whenever the AC system isn't running,but override the ECM control when the AC is running. To do so I plan to wire in a relay to control the fans as shown below:


Here is how I think this will operate:

Operation with AC Ctrl OFF:
- AC Fan Ctrl Relay and AC Compressor De-energized. ECM Hi Fan Signal provides ground to Hi Speed Fan Ctrl Relay to turn Engine Hi Fan on/off based on ECM control

Operation with AC Ctrl ON:
- AC Fan Ctrl Relay and AC Compressor Energized. AC Fan Ctrl Relay provides ground to Hi Speed Fan Ctrl Relay to turn Engine Hi Fan On whenever AC is running. Compressor runs at all times that AC Ctrl is On (non-cycling system).
- The ECM signal input is "floating" (i.e. not connected to ground or a load). Hopefully this does not trigger any ECM diagnostic codes.
- If the Ambient Temp Switch senses freezing air temperatures, the control reverts to “AC Off”.
- If refrigerant pressure goes below 30psi, the Hi/Low Pressure Switch opens, the control reverts to "AC Off"
- If refrigerant pressure goes above 406psi, the Hi/Low Pressure Switch opens, the control reverts to "AC Off"

I plan to wire this thing over the next couple days and hopefully I'll be ready to put a charge into the system by the end of the month.

TheBandit 11-01-2018 03:51 PM

While I was working on the wiring last week, I got a wild hair and decided to have a few parts powder coated. I went with textured black on the air intake tubes and radiator hold down and satin black on the hood latch. Those parts have been bugging me for a long time. Really happy with how they cleaned up!




I didn't snap photos of the wiring but I got that done too. I was faithful to the wiring diagram in my previous post. To test, I bypassed the safety switch and confirmed the clutch and high speed fan were triggered when the AC was turned on. Everything was working properly so I headed to a buddy's shop to charge the system.

My buddy runs a mobile refrigeration business and he kindly offered to lend his tools, time, and expertise to help charge my system. He has not worked with a POA system before so this was a little new to him. We started out by vacuuming the system down for about 45mins. His pump seemed to get us around 28 inHg.



Before I came, I had a plan for determining charge amount. I wanted to start by adding a low charge (around 2lb), then add 0.5oz increments of refrigerant while monitoring the high side pressure. I was going to look for the plateau where adding refrigerant did not noticeably affect the high side pressure. This would indicate the receiver was starting to fill with liquid. Then when the pressure began to rise again / spike, this would indicate the receiver was full of liquid and the bottom of condenser was also beginning to fill. Thereabouts would be my stopping point.

We started by adding the initial 2lb charge amount. The compressor and hi engine fan turned on as expected and we gave the system some time to settle. During this time the engine was idling, the blower was on high, and the compressor was running continuously. The blower was getting outside air instead of recirculating, because the factory system relies on vacuum controls and I don't have the vacuum hooked up yet.

As we charged, I noticed frost forming after the POA valve. This is normal behavior when there is a lot of suction from the compressor such as during low loads or low charge levels. The pressure drop through the POA valve makes it act like a second expansion valve and you get additional cooling downstream. Here’s a photo showing the frostline where the pressure drops after the POA.


At this point we measured the air going into the cowl where the blower was pulling from. It was over 107F due to engine wash. Then we measured inside the car and found 52.2F coming out of the center vents – not too shabby! Pressures were 27psi in the evaporator (where I set the POA!) and 145psi on the high side. Ambient was about 75F. The system was working and considering the cowl temperatures, I’d say it was working very well! All values measured at idle, blower high, outside air (non-recirc), engine fan hi, doors open, hood up.

If we had proceeded with the original plan, we would have added 0.5oz and continued to monitor pressures to see how things changed. But from here forward things went sideways. Instead of incrementing in 0.5oz, we added a whopping 0.55lb. Pressures went up to 38psi in the evaporator and 250psi on the high side. Yet somehow vent temperatures only went up slightly to 53.6F. Maybe I misrecorded that value because I would have expected higher.

With the high 250psi high-side pressure and no regulation from the POA valve, we thought we may have overcharged the system. So we began recovering charge in unknown amounts. Eventually we got the system back down to a steady 32psi in the evaporator, 165 on the high side, and 59F coming out of the center vents with cowl temperatures still over 100F. Unfortunately I was out of time and I needed to head home.

Where does this leave me? I have a questionable/unknown charge in the system now, but it does work. I think I’d like to get the recirc ducting working, evacuate the system, and start over with my original plan to determine charge amount.

I did take a video last night just starting the car in the garage. The car was idling, hood down, high blower, outside air, ambient just over 70F. I got a frigid 40F from the center vent! I’m most certainly happy with that! Here’s a video showing how the outlet temp came down when I turned on the AC.

TheBandit 11-29-2018 02:11 PM

Earlier this month I took the Nova to work.


There's something magical about the reverberation of a V8 idling into a parking structure. It brought back memories from taking this car to my high school prom and setting off all the fast & furious kid's car alarms as I rolled in. Driving this car to work makes my day so much better. It gives me something to look forward to at lunch and again at the end of the day. And I can't tell you how happy I am with the decisions & compromises I've made to keep this car comfortable and reliable as a driver; no big crazy cam, no overly stiff suspension, investment in safety and visibility, etc. The car continues to provide much needed therapy now two years since getting the LS swap running.

On that particular day, I took the Nova out for lunch and had my first opportunity to see how the AC was working. Weather reports said it was in the low 80s. Cruising around I was getting vent temps around 85F (ac off, outside air, hi blower). When I stopped, that would climb to around 90F. While stopped, a turned on the AC to see how quickly the vent temps would drop and to what level. Here is a video.

In the course of 30sec the outlet temps went from 90F down to 50F and stayed around there. This with AC on, outside air, and hi blower. 50F is higher than I'd like to see, but I think the lack of recirc is a big factor when pulling 90F air from outside. Here is what happened after driving the car:

It was hard for me to see while driving, but I think the outlet was around 42F. I don't know if most of that drop was due to lower inlet and under hood temperatures or more air flow across the condenser; I suspect the former. Later on the way home, with ambient in the high 70s, I saw 38-40F from the vents.


While I'm happy so far with the performance, I know I'm leaving a lot on the table using outside air. The factory system uses a set of vacuum operated flaps to direct blower air either from the cowl (current default) or from the inside passenger kick panel, but I haven't had the vacuum connected. So after that run I took the time to hook it up. I connected the vacuum supply with a reducing tee on at the back of the manifold, sharing the port with the transmission vacuum modulator. I also installed a heater bypass valve on the passenger fender.


The operation of this system is dictated by a vacuum control valve attached to left-most AC control lever in the cabin. In the "Max AC" position, vacuum should be supplied to the heater core valve to bypass flow to the heater and the duct flaps should actuate to recirculate air from the cabin. After I got the system connected, I had my 5yo daughter keep an eye on the recirculation flap in the passenger kick panel to see if it was operating correctly. What I expected was for the flap to open with the control lever in the "Max AC position" and remain closed otherwise. Here is a video of our test:

We found the recirculation mode was happening with control lever in the "Vent" position and not in "Max AC" or other positions. I'll have to investigate why this is happening. This probably will mean pulling the controls apart to test the vacuum control valve. I am curious if there is an adjustment or mounting issue that could cause this.

TheBandit 12-18-2018 05:09 PM

There's this thing that's been bugging me for a while...



My Walbro 255 has been getting noisier and noisier over the 2 years its been in service. It started as a reasonable wur but over time grew to a screaming whine. The pump is in a Tanks Inc PA-4 hanger/tray setup, which I modified to fit the original tank.


I decided to try a Deatschwerks DW200 (which flows 255lph) after seeing a few comparison videos of the noise on YouTube. I bought P/N 9-201-1000 which came with a universal inlet screen. Unfortunately the orientation of the screen did not work out for the location of my pass-through fitting on the hanger; the screen would need to be rotated 180 degrees.



After searching unsuccessfully for screens from Deatschewerks, I decided to give my local auto parts store a shot. I started by searching their online catalog for "fuel pump screen", sorted through the photos, and went to the store armed with a few candidate part numbers. Luckily I found one with suitable dimensions and 180 degree orientation that was perfect for this: Precision Fuel Pumps S13010.



With the screen on, it was obvious the pump was not going to fit between the tray and the pass-through fitting on top of the PA-4 hanger.


So next I cut the fitting a bit shorter and threw it in my Eastwood tube flaring tool to put a new bulge into it.



Problem solved!


The last step was to crimp new ends on the wire harness that came with the DW200 pump. This little harness uses absolutely puny wires. I think they are 14awg. I crimped on some F-style ring terminals and soldered them as insurance.


Here's the finished module with the new pump, ready for reinstall.


And here's a video of the results:

I'm happy to be rid of that embarrassing whine! Now back to driving the wheels off...



entropy 12-18-2018 06:02 PM

Well done!!
I still mount the pump & filter on the frame.
When the pump dies I just bolt the new one in.
Handy when your out on the styx :laughing1:


baxter 12-19-2018 12:13 AM

This car has came a long way threw the years! Nice freakin job!

TheBandit 12-19-2018 02:39 PM

Thanks e & Baxter! I enjoy it immensely.

CarterKraft 12-19-2018 03:35 PM

Great job, I may need that in the future. Its surprising how loud the walbro is huh.

TheBandit 12-21-2018 01:00 PM

The Walbro wasn't too bad when I first got the car running, but this Deatschwerks pump is considerably quieter. I can barely hear it prime before I start the car and can't hear it at all over the exhaust.

I took the car out again the other night and wow, what a relief. Now I can enjoy the pure, untainted melody of the exhaust. What a joy driving this car. Now I just need to find my next race!

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