Prelude conversion project - some questions

[jonescg]

Remove the rear two battery packs. Then put them back in afterwards

It should only be a mere 60 kg or so overweight if anything.

[brendon_m]

Ute chop?

[coulomb]

If it is overweight what can you do to make it pass?

More seriously, my understanding is that you might:

• End up with a lower luggage capacity
• Have to register it as an n-1 seat vehicle, where n is what you tried for last time (might have to remove seats and/or seat belts)
• Keep the same luggage capacity and seats, but beef up the brakes (e.g. larger rotor and pads) and possibly add some more structural support, as designed by the engineer. The brakes may need a fade test.

[brendon_m]

A Google shows Gvm is 1565kg
People and luggage is 81.6kg per seat
81.6kg x 4 seats = 326.4
1565kg - 326.4kg = 1238.6kg
Standard weight is 1060kg - 1340kg depending on model
You got 1100kg when you weighed it and presumably you are also going to ditch the spare tyre now.
Looks like you have some reasonable weight to spare.

[jonescg]

Correct, 1100 kg with the spare tyre and tools, and a full tank of fuel. So we should be pretty close to original tare.

[jonescg]

I had a friend knock up a couple of stainless steel fittings designed to perfectly match the 7/8" aircon male end.

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Next step is to braze these on with silver solder. One shot - no pressure...

[jonescg]

Silver soldered and re-plumbed. Ready for some aircon hoses now! I should read up on the compressor and make sure I'm about to fire it up correctly...

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[jonescg]

Today I pulled the bumper off and replaced the failed windshield washer pump. A sure fire way to fail the inspection if you ignored it. Luckily all the auto stores had some workable options.
I also finished the single phase 32 A EVSE. Literally just assembled it according to the instructions and it just works. I doubt the thing will see anything other than being plugged in for 6 hours and unplugged later on. WiFi? Nah. It's a glorified power point.

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Monday afternoon I will drop it off and the new A/C plumbing will be installed and re-gassed the following day. Francess picks the car up on Wednesday and will drive it around before getting new tyres on Friday. Then, with new hoops, new windshield washer, air conditioning, inertia switch... more compliances than you can shake an NCOP14 document at, it will go to the weighbridge and then around to the engineers office the following week, just in time for Christmas!

[brendon_m]

What a Christmas present!
Its even the right colour

[jonescg]

Hmmm, well Mick called to say the plumbing is in and the A/C is 90% gassed up, but they can't get the compressor to turn.
I wonder if a) I have wired it up wrong, or b) the A/C fuse is popped due to inrush current.
Either way, it won't be a cool car to drive until the weekend...

[jonescg]

So Francess picked up the car and drove off. About 15 km later, and maybe 10 degrees warmer, a terrible noise was coming from the front of the car. I dropped in on her at Subiaco after work and indeed, the A/C was working alright. Just very, very noisy. I'd say the guys at the workshop didn't see it spin up because it was either below 30'C and/or the delay of 15 seconds between switch on and wind-up had them fooled. Either way, the AC does work, but it really shouldn't be making those noises.

She drove it back to the workshop and the guys confirmed it's probably low on oil. It takes Pag 46 oil which apparently can be introduced without needing to degas the system. So we'll get around to that on the weekend. But I am really concerned that the scroll is damaged... I do have a spare compressor, but was hoping I wouldn't need to go there.

[brendon_m]

Normally a new compressor comes with a full charge of oil. You said you spilt some but the system should of had some in it (probably ROC oil from when it was retrofitted to r134a, which is compatible with basically everything). I'd guess there should be enough oil there to keep it working. For it to fail within 15min sounds more like a manufacturing defect or dirt in the system etc rather than low oil.
Slight oil starvation normally takes months to years to show up.

Or maybe the system is over pressuring. Sometimes compressors get really noisy when the high side gets too high but not high enough for a pressure switch to cut it out.

Also on a side note the original oil in the system while works as a lubricant theoretically should be flushed out anyway as it shouldn't be used in a high voltage compressor (you can end up with tracking to ground)

[jonescg]

Hmmm, well apparently it takes PAG 46 lubricant, which is far more common than I thought. Repco sell it in spades.
It actually does sound like the scroll is off balance though. And it's not impossible there was a mud wasp next in the condensor...

[brendon_m]

While not ideal, a wasp nest in the condenser wouldn't be the end of the world. There's a filter and a TX valve in the way before anything gets back to the compressor.

Interesting on the oil, I guess the Chinese just don't care about stray current

[jonescg]

Reading the manual which came with the compressor, it seems 75 dB is normal at full speed. Is 75 dB a lot? Well a pneumatic orbital sander at full speed generates 75 dB. So yeah, it might just be normal...

[francisco.shi]

A mechanical scroll compressor is very quiet you can hardly hear any difference when it comes on. An electric one should be equally quiet.

[Rusdy]

Reading the manual which came with the compressor, it seems 75 dB is normal at full speed. Is 75 dB a lot? Well a pneumatic orbital sander at full speed generates 75 dB. So yeah, it might just be normal...

Out of curiosity, I googled the dB comparison graph. Apparently 75dB is pretty damn loud!

Which makes me more curious, is the loudness because of the compactness?? As my outdoor unit for home air-con 'only' emits 68dB (that's the lot with the fan on) according to the name plate. Comparing to Nissan Leaf's air-con compressor, the loudness of my home air-con compressor is roughly the same (minus the big fan noise).

[jonescg]

Yeah, it is set to a constant speed of 5500 rpm, which means it cycles on and off a bit more than if it were set to just 3000 rpm and runs near constantly.
I'll try and adjust down the speed, but I have a feeling it might be fixed.

Compressor noise.JPG (149.13 KiB) Viewed 478 times

[brendon_m]

Doesn't the pwm input adjust the speed? And is it pwm or just voltage input? Ie could you use a couple of resistors to drop the voltage on the enable line to slow it down?

[jonescg]

Doesn't the pwm input adjust the speed? And is it pwm or just voltage input? Ie could you use a couple of resistors to drop the voltage on the enable line to slow it down?

It is PWM control between pin 3 and ground, but the sales rep says because I chose a fixed speed, it can't be adjusted. It's likely there's a PWM generator onboard already, so I just need to get inside and change it. I will mess around with the other one first, however I understand spinning it up without refrigerant or oil is a bad idea.

[brendon_m]

It can make a mess and it's not good for it but 10 seconds isn't going to kill it. There's companies out there that make endless air kits for 4wds. They just grab an a/c compressor and add a filter to the intake and an air fitting to the discharge port and bam, you can pump up wheels all day long.
To be fair the "pros" also add an oiler kit to the inlet but I've seen a homemade job work for 3 years pumping up tyres every weekend without any lubrication and then put back into aircon service. (admittedly it wasn't the quietest compressor....)

[jonescg]

So Francess had the PAG46 oil added and had the gas added, but the compressor is as noisy as ever. Today, she turned the power of the charger down to 3.6 kW hoping to divert sunshine into the car, but the A/C compressor was taking all of it, leaving nothing for the battery! In the end, because the cells were still sitting at ~33'C she just disconnected the A/C control wiring and let it charge up. 33'C isn't going to hurt anything, and considering it's 41'C today, it's probably doing very well.

[jonescg]

Oh, and according to this, it's not just me. Early Model S had very noisy A/C compressors and fans: https://teslamotorsclub.com/tmc/threads ... sor.31877/

[jonescg]

After our lunch at the Kewdale Tavern, Frances and I swapped cars so I can take a look at the Prelude's A/C and how it's operating. Great day for it, only 41'C in the shade.

The good news - the cool cabin air is very nice, and the heat exchanger is doing a great job of keeping the battery nice and cool.

20191214_161025.jpg (180.12 KiB) Viewed 413 times

The bad news - I'm pretty sure the compressor is broken, judging by the noises it makes and the vibrations which carry thorough the chassis.

[jonescg]

Another frustration is that the AC relay won't turn on unless the temperature of the battery pack is over 30'C. If you look at the new diagram, you can see it should still operate by pressing the button provided the key is on, but so far does nothing.

new Aircon wiring5.png (252 KiB) Viewed 396 times

When I disconnect the Arduino relay output which normally supplies power to the A/C compressor, pressing the cabin A/C button does fire up the fans, but not the compressor. I wonder if there's too much voltage drop across the coil and the diodes?

Also, the Arduino is bouncing at 30-31'C between on and off, so the compressor is firing up and stopping a lot when it's right on the threshold.

I'm beginning to think it might be easier to have the AC work with manual control only, and not have it come on during charging unless manually allowed to...