Was this issue ever resolved?? I have same problem.

And yes, I also have a clonned tech 2 lol

 

I don't believe he's figured it out yet.

you can try following the trouble shooting info above but can also start a new thread too. here and or the Tahoe board under hybrid. there's not a lot of owners of these left active on the boards thou.

 

Aahahhaha! I got it, finally! ...this is gonna sound crazy and I frankly don't know what I did, really, I just know what worked. As I mentioned before I tracked the lack of isolation problem to the air conditioner compressor coils, both the positive and negative side have only about 100Kohm of isolation to chassis. Need at least a mega ohm or maybe 2 to pass the half bridge voltage tests or so they say. I highly recommend a 5000v isolation tester from amazon or ebay (something that will probably not get used very often so I can't see getting a good fluke). The darn thing worked like a champ to trackdown high impedance shorts.

Whats interesting is you can't get the system to close the contactors to check the half bridges so from what I can tell there is no obvious reason why the computer won't command the contactors closed without updating that measurement. So I kept fiddling. Over the past 6 months I got the truck to start three random times, each time after doing something with the 12V battery (i.e. replacement or recharge). But it in all cases the new AGM battery was just putting out normal good 12V and has always past the load tester. In all my computer play the battery has been running about 12.8V after a recharge and might get down to 12.2v before I boost it back.

So get this I tried several times to reset the 300V present DTC using the GM tech 2 clone. There is no feedback one way or the other, but I turn the key too acc. still no 300V contactor close. So then I put a charger on the battery and boosted the voltage with a 20amp charge to bring the voltage up almost to 15V, hit 300V present reset (with the charger on the battery, something people tell you not to do or you'll trip the crash sensors), and then all the sudden I see the status showing the contactors closed! Wahhhaa?

Now the truck starts just fine and runs completely, I mean completely code free with the AC disconnected. Without the battery charger connected, starts and restarts all day long, I've driven it over 500 miles, runs perfect.

What is interesting is the AC was working the computer just didn't like the low isolation and threw the P0AF0 and 1 codes, I guess now that I read about it is caused by moisture getting in the freon over time. I wonder when they did the engine rebuild if they put PAG oil in it rather than POE?

None the less, GM wants $2K for a new compressor, but there are ton of used ones on ebay (I guess as these hybrids hit the junkyard there are currently a derth of parts).. So I ordered up a $75 compressor, $100 manifold kit/vaccum pump, some freon, and a bottle of POE oil. Now I just have to figure out how much of each to charge the system and find some more time to get under the truck!

...I will send updates. I am not sure I want to reconnect the compressor and re-cause and re-correct the fault just to confirm the clearing sequence or not for all those who will come after me. After all this I am just happy it starts again!! waahhooo!

What I did notice is that the contactor close command was at about 65% vs. 20% on the bad truck vs. good truck. After boosting the voltage and getting the contractors closed the command was at 20% on the bad truck. What that "command" status percentage is or represents I have no idea.

I suspect something is referenced off the 12V system for measuring and clearing some "constraint" to commanding the contactors closed and that by boosting the voltage temporarily I got it to pass the test, but once cleared even if I let the truck sit for a week it starts right up with no battery help. Beats me, if anyone knows why this is it would be good to know as I can tell there are others who will fight these issues after me.

If your working on these, just know all this circuitry is very sensitive, you will read about people cleaning ground points etc to get them to start. I actually don't know if the 300V present DTC was a condition at all or whether I just got it past "its" sensitivity to clear the constraint and then ever after it didn't matter as long as the failure had been removed from the system.

...anyway I will get to work on the AC when I have time and report back on that. If anyone knows how much 134a and POE oil I'm supposed to put it in that would be helpful. None of the published fill charts seem to have these vehicles.

-Tom

 

Very nice.

Very common issue with all electric compressors is contamination with PAG oil instead of a high resistance POE.

Before replacing components, you will need to flush everything. The compressor may be fine, it might just be that the refrigerant is contaminated, and you have conductivity. IIRC, POE resistance is 10MΩ.

 

I bet you're right. going to be a pain to flush.. the shop that did the engine swap probably doesn't know or care about hybrid and just used the same recover/charge machine. I hear good hybrid shops will keep a 2nd one just for electric compressors. I do wonder how much is to much oil in the system. if just a cross-contamination will do it or if they injected a couple ounces of oil

definitely replace the dryer, and I've read on ac sites the new style parallel flow condensors can't be flushed well. so replace that too. the rest as Keith said, buy a good flush kit and go to town. if you can get the refillable flush gun and buy the flush by the gal, it used to be cheaper that way. the behind the dash evap should flush, the rear one, it's got an expansion valve on it, and I don't know if that will. if they are cheap I might replace that too.

for the capacities, I don't remember. caddy didn't do the long Suburban length one as a hybrid right? they use more. I can look it up, but it should also be on the front radiator cover. my yukon did but remember it's in kg and the , is a decimal point for some reason I don't remember haha. I don't remember about oil, but I can look it up for you.


thats awesome you got it working. I'm pretty sure mine has had the high side core replaced before I got it. replace both of those and the caps with new one from gm while you're in there. the auto parts store ones always leak from what I found. but my high side cap was blue when I got it. I hope whoever did it knew what they were doing haha. or this might be a useful thread to me someday.

 

my software days 2.5lbs (1.1KG) r134 and 5.00oz (0.1L) POE oil.

edit*
I said dryer, but it's accumulator that needs replacing.
there's 2 tab's listed for the hybrid ac specifically.

PIT4669D, you can probably Google it, if not I can screen cap it. but there's a reference to how to flush if the shop added dye, because the dye had pag on it.
flush document ID# 2047704
ac compressor oil balancing document ID# 2105559

 

Interesting. I hadn't thought about PAG oil being a little conductive on its own, I just figured it would absorb moisture easier and hence why they came up with a new formulation, but oil I would think is naturally resistant to water no? ...so I think I see where your going with that thought.

I assume they had to remove the AC when the swapped engines. So I guess the choices are they put PAG oil in or its just getting old and over time moisture has penetrated, The engine was put in April of 21, and has 30K miles on it. So its been 20 months since the engine swap to failure, but thats pretty good if it has been running on the wrong oil. I really don't want to get into a whole air conditioning saga. ...so I should consider this for a second before going to far... ...or maybe the investment in parts really isn't all that much to just take a shot at it. I do have to wonder if the compressor I have is just fine. Once I have the oil out of it I can test it to see if is back to good isolation assuming you can get enough of the oil out.

So if PAG oil has some conductivity shouldn't it cause issues right away? Maybe the time to onset of the issue suggests that it is indeed POE oil in there? haha maybe I can just isolation test the oil for grins. How does one flush this, all the docs suggest a GM flush system something like ACR2000 or something they call it? Doesn't the accumulator dry the system? Should I replace that? If you flush it you have to, right? I assume a flush is something I have done to when I get the old freon removed, but again that would have to be a dedicated hybrid shop not to get an "incompatbile flush"?

From GM : • Use only the GM-approved POE oil in this system. The GM part number is 88862657. This part is a 3.5-oz tube of injectable oil that’s packaged with a desiccant inside a foil poly bag. This special POE oil is intended to be used with the J-45037 A/C oil injector and the GE-48997 A/C POE oil injector hose.

This indicates a soon as the system is opened, I should just go like hell to get it back sealed and evac'd as opposed to drive it somewhere for a flush? I was just planning to pull the compressor and bolt up the new "used" one after pouring in a load of POE oil in it and see what happens. But now you have me wondering...

-Tom

 

flush is just a liquid basically like brake clean, but not. low evaporation temp and solvent to oil. so what's normally done is you always replace the dyer/accumulator. same part, 2 names because they have desiccant pellets in them to suck up any moisture in the system vacuum can't get. this one seems to have a special dye pack in it too. but it's a disposable part. any time you open a system, standard practice is to replace that. plus a lot of oil is in there. you can't flush that.

there's no need to rush till like the very last part. you're going to use compressed air for the flush process anyways, better would be a nitrogen tank and it's talked about in some manuals but no shop has nitrogen tank in real life for ac.

so you pull the dyer off, the flush gun is just a tank you fill with solvent/flush. then pressurized with air, it had a hose and a hand valve like a blow gun style, you stick it to the intake side of the evaporator, or lines or whatever you want to flush and pull the trigger, it shoots high pressure flush thru the part. it makes a mess coming out the other size lol. the pro way is a machine that hooked up to do and recover the dirty stuff but I honestly doubt even a dealer shop would have it or actually use it.

so you flush each component. as said before you can't flush the dryer and can't flush condensor. both should be pretty cheap to replace. those new will come capped off under a vac, that's part of the rush at the end. flush and blow out what you can, if you can find that document about balancing the compressor oil, I can't find it quickly, but you'd do that. replace the orifice tube. get everything mounted, and then pull the caps off, spread your 5oz of oil around the system as you can. since you won't have a recovery machine to inject it for you, then connect everything up and start pulling a vacuum. I run mine for an hour, but they say 20min is fine. then fill with the correct amount of r134.

it's going to be a hassle and make a mess, and I don't know if you need to remove the compressor to "balance" the oil, whatever that means, but on a belt driven, normally you'll pull the old compressor, drain as much oil out of it as you can, and measure that, say you get 2oz out of it, when spreading around your 5oz, 2oz of fresh would go in the compressor while turning it by hand.

or, I do believe Keith when he says it's pretty common. if you can find a ac shop that's used to dealing with electric ac's like say a prius shop. they are probably familiar with the process and it might be worth it to just pay them. even thou I have access to a AC recovery machine, it's full of pag and I'd probably look into just paying a shop to do it for me haha as long as they don't murder you on the price.

right now napa lists a condensor for 177$ and a accumulator for 67$. they are usually on the higher side and you'd have to confirm it's the hybrid correct. I might just get the accumulator from the dealership to be sure or gm parts direct​, the condensor should be the same as long as the physical ports fit. a flush kit for 69$, qt of flush for 15$. probably find all those cheaper someplace else too.

 

Alright, next problem. I followed all the instructions here, replaced the accumulator, condenser, and put in my ebay'd 2009 compressor. I put ~5 oz of new POE oil distributed around the system reconnected everything right after putting in the oil and started pulling a vacuum. I was able to pull -29 inHg and I let it pull for probably a total of 4 hours in between cycles. Turns out the Amazon manifold set didn't come with the proper adapter to R134A. Ended up having to get the can adapter at Autozone and the Can to 1/4 flare adapter at Grainger (this was the hard one to find, surprisingly). So after getting all that I've put in just north of 2 and 1/3 12 oz cans of 134A. I started the engine, it started right up after a false scare where I forgot to press the darn 300V disable lever down!! DOH! again the code scanner should be that the interlock was somehow open, I guess after a month or more of not playing with it I had forgotten this important step. Anyhow, I got 7 PSI on the manifold gauge, the compressor won't start and run. When I compare the live data between the good truck and this truck all are exactly the same except the pressure on the HVAC control module -> Hybrid shows 17.49 psi vs. 52.74 psi and the "Low refrigerant pressure detected" is Yes vs. No. Also on bad truck I get an "evaporator air temp desired" of 188.6 vs. 42.8 deg F. Odd thing is when I shift from full cold setting on the HVAC panel to full heat the desired temp goes to 42.6. Of course the Bad truck has 0 RPM on the compressor while the good truck has 2760 RPM. Other wise all other parameters across all live data fields are pretty darn close to one another.

I am guessing somehow I have to get the compressor to come on to get it to finish loading enough 134A to get over the low refrigerant pressure detected "signal". Dunno what keeps the compressor from running.

Any other theories or advice would be appreciated. If I can get this to 'cold' air I can declare this saga over!

Thanks again all! I never would have sorted through all of this so far without you all!

 

yeah, you're low. you need 2.5lbs if I remember correctly. 16oz to a lb. was always. annoying they didn't sell the cans in 1lb sizes, instead of 12oz.

do you mean it stops taking frezon? or you stopped. if the scanner or gauges are showing 17lbs on the low side, it will take more, the can should have a good 50psi in it at room temp. an ac machine will shoot in the amount you set it to, using cans you run the ac and put the rest in on the low side, or I've heard you can heat the cans in hot water to get the pressures high enough to get it in. I've not done that, cause running it is usually easier.

when you start the truck with the gauges on it and ac on max, what do you see the gauges do? if nothing, try clearing the low frezon dtc. im hoping it will turn the compressor on for a atleast long enough to see the low side drop, at that point open the can till you get the full 2.5lbs in it.