2seater

I know this has sort of taken on a life of its own but it appeals to my curiosity. I did a quick hand plot of the readings I posted.and I noticed a couple of obvious outliers. I think I will try this in reverse based on the predicted values from the online calculator to see how close it is. The high temperature area seems pretty smooth, even done by hand, so I will try just the lower temperature area.

Unfortunately it is unknown how close the readings are to the borders between cells, so that may be part of the issue in getting a precisely predictable curve. I am sure it is reasonably close, and of course more data points in the calculator would probably help too. In a perfect world, a series of trimmers in the desired ranges, or maybe a ten turn pot, plus a way to watch as the dashboard indicator changes would better establish the center of each cell. The ECM is decoded pretty well. Too bad the BCM isn't. On a related subject, if this drift is normal, how well can we trust the plethora of other similar ones, all through the systems, coolant, air temp, even in the MAF? I'm sure GM expected some of that, but maybe not for going on 30 years

I should have switched to a lower resistance pot as the 10k gets really fiddly down low, but it worked out okay. This what I found: k ohms indicated temp. *C 2.918 23 2.660 26 2.390 28 2.110 31 1.885 33 1.784 35 1.675 37 1.555 39 This my plug for the sensor with pins inserted. Maybe not the best choice for background but you can see it is different than any illustration or photo I have seen?

Well, it's in the fifties and raining right now, so a little time in the garage would be a good diversion. Welcome to the first day of summer.

Yikes! I think I got lost around the second line, but the calculator is pretty cool. I must admit, the two different curves shown are a bit confusing, at least to me. It looks like the calculator sort of idiot proofs it though giving hard numbers rather than trying to interpret the curve. Would it be helpful to widen the range of the readings or hone in on the areas we are interested in? I am guessing that temps. around normal ambient would be what users might first encounter, engine off and after sitting for a while? The two readings that both indicate zero were discovered by accident and not by plan. The trimmer pot is not the easiest to finally adjust with Homer Simpson fingers :)) If we have enough data, I am good with that too.

Just guessing from the color, the cast piece is some sort of pot metal but no evidence to back that up. There is more than one grade of aluminum, at least the hardness or ductility level, but I would guess this a lower grade casting. It doesn't seem to be the best design with a smaller clamping surface than it could be with the counter-bore on the lobed side, leading me to believe it was a press fit, not cast in place,.

I have no idea but I would doubt it. I think the sun load is likely a separate input the climate system uses to adjust the perceived interior temperature? This test should have isolated the sensor input to the BCM to simulate the variable resistance of the thermistor in the line? I should add this was with key on and engine off. I imagine this could spoof the system into running as long as the resistance value was set above -1*C as long as everything else remained in range but didn't seem like a good idea.

I decided to try an experiment to see what my particular car sees as indicated low side temperature. I disconnected the plug at the sensor, made two small copper pins to insert in the connector and connected a 10k trimmer pot across the pins. I adjusted the pot. to various resistance levels and read the bd28 indicated. I would then disconnect one side of the pot. and check the indicated resistance value. This by no means complete as I was doing this alone and a lot of back and forth had to be done. The reason I say this is there is definitely a high and low value for each temperature reading, so a helper would perhaps provide an easier way to find the boundaries but I hope the result below will provide basic usable information: Resistance indicated temperature Open -39 9.96k -2 9.67 -1 8.99/9.17 0 8.64 1 8.18 2 7.46 4 6.97 5 6.72 6 6.57 7 6.17 8 5.63 9 5.57 10 2.62 26 this matches the high side indicated

Looks good to me. Interesting to see apparently there are two designs, one with a flat area and one with all rounded?

Just to clarify, my layout is exactly as above, except spread out over a larger area. The pressure switch is located approx. where the high side temp. sensor is shown and the hi-side temp. sensor is to the right of the blower motor in the view above. The locations on my FSM drawing are in the correct locations but labeled incorrectly. I do not know if it because my '90 is early production, last four of vin 0145, or what it is? For example: my trunk light bulb doesn't match the FSM or any bulb chart I have ever seen. It is a single filament. non-polarized, two pin bulb, #1004. No case ground? The occasional discrepancy does make repairs a little more difficult. Like the bulb above, I ordered a few small led replacements, for interior and exterior use, and then find the listings are incorrect when making the change. It does get annoying and leads to delays. My thanks to everyone that has helped me get this sorted out.

Sorry for the delay, I was at my cottage for the weekend. No internet and my phone is barely literate. Yes, it is the standard 1990 Reatta/Riviera FSM. Thanks for everyone's patience

I agree completely. I used the term ASSuming my manual has simply reversed the labels, but it is certainly more than that. The sensor near the blower motor has to be the high side temperature. The one just after the orifice tube and before the evaporator should be the low side temperature. The low pressure switch is pretty much midway between the two temp. sensors in the larger return line. All of my connectors are similar and unlike the ones shown via photo or illustration in the manual. 10-4. It explains the similarity in readings.

I replaced the battery in the temp. gun and ran a few tests. I locked the throttle at 1500 rpm and set the desired temp. to 60*. The 28 reading cycled as before -2* - 10* and back. The lowest observed temp. at the low temp. connection was 44*F. The center outlet temperature settled at 56*F and stayed almost constant. Despite the hot air from under the hood, the inlet air was only 92*F. After ten minutes or so the #28 low temp. reading would stabilize at zero for 15-20 seconds but mostly it continued to cycle. This at least gives me a baseline to see if this improves when the compressor is replaced and properly charged. I checked the resistance at the two sensors, low pressure and temperature. I found 2967ohms @ 77.2*F on the temp. sensor and 2894ohms @ 77.3*F on what should be the pressure sensor. Strange that they look the same, have the same connector, and read so similarly if they have completely different functions.

I don't see any issues with the stock plumbing, steel or plastic, at any possible pressure the fuel pump can generate. I wasn't suggesting using that particular high pressure pump, maybe a poor choice as an example, but just a representation of the information needed for a non-stock application. Even if the pump is capable of 100 psi, the regulator on the fuel rail will control the actual pressure bypassing the excess back to tank. Just a rough example for a boosted engine of about 300hp: A safe estimate of fuel required is 0.6# per hour per horsepower, so 300hp x .6# = 180# per hour of fuel required. In this case, the pump is rated at liters per hour, and fuel weight is approx. 1.7# per liter, so 180# / 1.7 = 106LPH required @ 60psi. I am making the assumption for this example that an engine similar to ours will require 15# of boost. The fuel pressure regulator will go both directions, decreasing the pressure in the rail in response to engine vacuum and also increase pressure in an approx. 1:1 ratio in response to boost, so it should peak near 60psi at full boost pressure, using the 43.5psi standard regulator. Since this is a six cylinder, the injectors would each supply 1/6 of the total, so 180/6=30# at 100% duty. Using a safe 80%-85% duty would be 30/.80= 37.5# injectors required

I think 89RDG has the right idea, take a photo, it doesn't lie, but unfortunately, it too can be reproduced over and over, correct or not I guess to use the manual requires a basic knowledge to know when they are correct or not. I definitely have a sensor in the liquid line, located as per my FSM diagram, which I must assume should be the pressure switch, but it is odd that it had a similar resistance readings to the others posted above? I guess I will get my temp. gun charged up and do a little more in depth before I post back, which may be some days.

It would be nice if they listed the performance curve of the pumps so it would be easier to make a judgement if it can supplied the needed fuel for an upgraded combination? Something like this from the Walbro I have been using for years. This isn't a recommendation, just an example of what I mean. I couldn't find the performance curves I have seen before but illustrates what I mean. Personally I like the idea of the turbine as long as it has enough grunt. If there is a replacement designed for the later S/C engines, it would likely be just fine. Fuel Pump: GSS340 The Walbro high output in-tank electric fuel pumps are available in flow ratings of 255 liters of fuel per hour. These particular pumps flow significantly more fuel at higher pressure. For example, at 80 PSI the standard 255 lph pump will flow around 132 liters (35 gallons) per hour. At that same 80 PSI the equivalent HP (high pressure) fuel pump will flow over 210 liters (50 gallons) per hour. Walbro in-tank electric fuel pumps utilize a proven gerotor design. The outside dimensions, however, are compact enough to fit existing hanger assemblies, without modification. Coverage includes most popular Acura and Honda, and many other Import applications. OPTIONAL UNIVERSAL INSTALLATION KIT: While the pump is available ala carte, installing this pump without adequate virtually pre-filtration guarantees early failure not covered by warranty. Installing this pump with an old filter can lead to similar results. The universal installation kit offered as an upgrade to this pump features one of our depth media filters. This media acts as a wicking mechanism, feeding fuel to the pump even when the filter is only partially submerged. Also included is our GSS wiring harness that allows you to make safe, secure electrical connection to your new pump.

Interesting. As you can see by this diagram from my FSM, #6 is labeled as the low temp sensor. #1 is supposed to be the pressure sensor, but it appears identical, including the plug, to the sensor I measured before. I am sure your diagram is correct, as that location is after the expansion tube, so it makes perfect sense. The funny thing is, the connectors shown lower on the page, match the style you showed, but they most definitely are not. Apparently there is an error in my FSM, at least on this page Aww, nuts, I cut part of the legend off.

Unless I am measuring the wrong sensor, mine has the connections reversed? The sensor has a single female cavity with two pins and the plug is a single male w/two sockets and a lock on both sides? If it is the correct one, upside down just to the drivers side of the blower motor, I find 2562ohms @ 82*F. or 27*C. In or out of range is unknown and I will need a new battery for the temp. gun, the laser is iffy. I will measure the operational temperature relative to indicated as soon as I get a chance.

Interesting. I will give that serious consideration.

Thank you so much. That makes perfect sense and I think I now understand the goal. I did a little more investigation and unless I disassemble a few engine air intake items, items not shown in my signature photo, access to the low side fitting will be essentially impossible. I am preparing my other engine for installation and that seems like a good time to install a new compressor and sort of start from scratch. It will have a different turbo setup and should have better access to the low side fitting although I can operate the engine N/A until the a/c is completed. It appears the present compressor is seeping oil so I figure it is on borrowed time so I tend to limit a/c use until it will be changed.

I certainly understand checking the accuracy of the sensors, but that wasn't what I was noticing in the two reference threads. It appears the reaction to over and under charge are opposite to each other depending on which refrigerant is being used. That may be completely true, but could have you chasing your tail if following the wrong directions.

Perhaps there is a difference in the reaction of R134 and R12, but the information from McReatta, R12, and drtidmore, R134, is opposite regarding the charge level? The R12 thread mentions temperature cycling as undercharged, and the R134 indicates overcharged if cycling?? I guess I will put the gauges on it as it is then easy to add if I need to. Thanks for the tips and I did watch the videos too. The price for the compressor in the Reatta store makes a rebuild less likely, just need to change plugs.

10-4 Dave. That sounds about right. Now if you guys would just teach me to do a better search, that would be golden. Thanks much for the guidance.

Thanks Ronnie. It gives me the info. I need. The post I was looking for is newer but very similar. I suspected my readings indicate a slight undercharge, which this tends to confirm. The one downside to my turbo setup is the difficulty getting to the low side fitting. I made every effort to make it accessible but even so, it is asking for blisters if connecting while pipes are hot Related to this: has anyone rebuilt, or resealed their own compressor? From the rash of bad rebuilds I remember from a while ago, I might try it on a donor compressor from the beater '89 I have.

I have searched using different terms but have come up empty. There was a thread in the not too distant past regarding the temperature indicators, as stated in the title, for determining the refrigerant charge level. The FSM has little to say about it aside from the readings for the points the compressor will turn on or trip out. I still have the original R12 system which seems to work reasonably well, and a complete gauge set, but the readings on the move seem like a simple check under actual conditions. Just for reference, it is warm here today 88*, with high humidity 78* dew point, so I thought it would be a good test. At 2000 rpm and 50mph, the high side, bc27 remains around 40*C and bc28 cycles between approx. -4*C and +10*C. I think I may have made a mistake on the desired temperature setting which was 65*F. I think this temperature range is wider than was suggested in the previous thread. Any insight?