New Engine Installed - No A/C

Hello, I need some guidance.

A friend and I put a "new" engine into my 2013 Persona with 126K miles due to a cylinder #2 start-up misfire that was found to be a head gasket leak. The engine had never been overheated, but oh well - seems like a common failure mode.

After the engine swap, the engine/hybrid system is all working great. I have no ECU codes, it runs strong with no misfires/rattles/etc, and because we cleaned all the components pre-installation (e.g. EGR & intake, and put in new spark plugs & EGR, etc...). I may be seeing a slight bump in mpg (~1-2 @ 75mph) but that's not important to my problem.

Unfortunately, I have no A/C - the fan blows ambient air and I think the compressor isn't kicking on. We carefully hung the A/C components during the motor swap and didn't think we damaged anything to cause a leak (but of course this is possible). The only connector removed was the small communication connector on the top of the compressor, not the high-voltage line to the inverter.

Work done so far:
1) Checked the fuse panel under the hood as well as in the driver's footwell and the fuses related to A/C are fine.
2) Inspection of the sight glass on the left side of the engine compartment on what I think is the high-pressure line. I don't know what to conclude, because I never looked at it before. I think I see liquid moving but no obvious bubbles.
3) I did the "hold down AUTO and recirc" trick and I got a flashing 72, which means "A/C INVERTER HIGH VOLTAGE OUTPUT SYSTEM MALFUNCTION." I think this could mean that either the high-voltage fuse in the inverter (the $50 one) could have blown, the compressor decided to die as a result of all the handling, or perhaps contamination/moisture got into the plug on top of the compressor causing a short. I have not yet opened the inverter top to inspect the fuse, as it was raining the past two nights.

I wanted to ask if anyone has other ideas before I start playing with the inverter, or a similar experience?

Thank you very much,

~Eric

 

Thank you both for replying.

No, not yet because: a) I have not concluded there was actually a loss of R134. The a/c system worked well before the engine swap and the code on the HVAC is pointing towards something electrical going on.

Interesting. So you ran the car with the 6-pin connector plugged into the compressor (I will remove and double check to make sure it is all clean/dry inside) but with the orange high voltage cable removed. While it makes me somewhat nervous that you ran with the open high voltage exposed on the back of the inverter, it seems like it worked for you. I wonder what that was doing in terms of the car's logic to then fire up.

 

Update: A/C is NOW WORKING!!!!

Thanks for the replies and suggestions.

I didn’t try the hot plug idea, but after getting back into town from "Christmas with the family" this morning I decided I’d start from ground zero and go step-by-step.

My initial thought was the high voltage fuse in the inverter:
1. I disconnected both batteries and let the system bleed down. While it was bleeding down I removed the 6-pin connector on the compressor and used some electrical contact spray and dried it using my shop vac to create air current.
2. I removed the top of the inverter (L-bracket) to expose the high voltage connections and the fuse. The fuse looked fine, but I removed it anyways and using my ohm-meter confirmed it was okay.
3. Then, reattached both batteries and verified basically nothing had changed. Still got code 72 in the HVAC test and the compressor wasn't kicking in.

Okay, so now what? I still wasn't going to try the hot plug idea, but thought that maybe there needed to be some handshaking between the inverter, compressor, and HVAC controls? Or maybe the HV connector at the compressor wasn't clean or got damaged when the engine bay was reassembled? Or maybe just needed a hard reset of the HVAC? I didn't know for sure so I did the following step-by-step. You'll see later that it may have been just the last few steps, but since I'm not 100% sure I'm posting everything I did at the risk of looking stupid(er)....

1. Using small probes and a Fluke 87 multimeter, with car on and running but A/C button off, checked high voltage on both sides of the connector near the compressor.
2. Turned A/C button on and confirmed high voltage on both sides of the compressor. In both cases, the voltage was fluctuating some (which seemed odd to me), but at least I knew I had voltage to the compressor; I did not know if it was enough or whether it had enough current to go along with the voltage when asked for.
3. Turned off car and disconnected both batteries again and let bleed down for 10 mins.
4. Disconnected both the 6-pin and high voltage lines to A/C compressor.
5. Reconnected both 12v and hybrid batteries, and started the car. Still had HVAC code 72 and somewhat expected a communications error but nothing new.
6. Turned off car, and reconnected the 6-pin. No change.
7. Disconnect hybrid battery again and wait to drain (10mins), and reconnected the high voltage compressor connector.
8. Reconnected hybrid battery.
9. After everything was put back still had code 72. Ugh.

---Now, I think if I had started with the next step I may have saved myself 2 hours. However, I do feel like I've at least made sure everything else (except for refrigerant) looked in good shape.---

9. With the 12v battery still connected, I pulled the 10A A/C fuse (fuse 31) in the under hood fuse box and waited for about 2 minutes.
10. Put fuse back in, and HVAC code 72 had cleared and got 00. Did not hit A/C button yet.
11. Turned off car.
12. Turned car back on and hit the A/C button. A "strange" sound not heard since the engine swap was heard, and the air got cold quickly. The compressor had come back to life. Woot!

It looks like when the HV line to the compressor was disconnected during the engine swap, it put the code 72 into the HVAC memory that wasn't coming out with simply disconnecting the 12V battery - rather the fuse had to be pulled and reinstalled with the 12V battery connected to do more of a hard reset of the HVAC.

SO, I think it was the hard reset via the 10A fuse #31 that ultimately was the secret sauce. But, going methodically and verifying the HV fuse in the inverter and the various voltages helped me to be more confident that a connector or cable hadn't been damaged during the engine swap.

Now I just need to replace the front sway bar links and the right side tie-rod end due to torn boots and she'll be as good a new. Although she will probably need an alignment.

 

From the various threads and YouTube videos I watched they seemed to suggest waiting 10-15 minutes for the high voltage to discharge (for lack of a better word). I realize that opening up the L-bracket on top of the inverter opens up a switch and technically leaves it safe but since I did not have isolating gloves I didn’t want to take any chances - and in later cases I was not working with the L-bracket off and thus needed to give the system time to discharge.

 

Re: a scan tool, all I had was a simple OBD2 scanner and I don’t recall it being able to see the HVAC module. Thus, the only way I was seeing the HVAC code 72 was via the holding down of Recirc & Auto during start-up I need to consider something better going forward. Do you have a recommendation?

Re: trying pressing Front Defrost and Mode simultaneously, I did read through that Repair Manual and saw that for the Prius it was Front Defrost and Mode - but it didn’t work for me and so I didn’t mention that. I probably should have (I’ll try and edit) as that is probably what triggered me to try pulling the fuse while the 12V battery was still attached.

Thanks again for all the support on this forum! Now I just need to decide if I want to try swapping out the head gasket on the old engine when I have time.