Interesting stuff - truck air conditioner unit board

[Behemot]

Got PCB from brothers truck air conditioner unit. It seems to be Waeco CA-800. So far I have discovered it is 24V powered unit, obviously with step-up transformer - transforming most likely to 230 V for compressor and maybe also the fans (at least two fans in there).

From what I know, board is defective for most people with this unit and it is supposedly worth of at least 400 USD/300 Eur, so you can see there is some point in repairing this thing

In this case it is supposedly dead, connecting it directly to 24 V resulted in burning two fuses. I have nothing but camera with me here (at home now) so I will clean it and take some pictures for you guys, than I will check all the diodes/rectifiers and transistors when I will be back to my "lab"

Stay tuned!

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

Man its covered with some stuff, it seems like dust with some pitch-like thing most likely from other cars and trucks exhalations. I cleaned some after half an hour of fun with technical gas, but still…

[budm]

Re: Interesting stuff - truck air conditioner unit board

It looks like it uses permanent magnet 3-phase motor drive system (you can see 3 pair of MOSFETs on one side of the heat sink) for the compressor, transformer is too small to be stepped up to 230V, this unit consumes 800 Watts of power. So far cannot find diagram yet.

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

Didn't find much too, not even any information on spare parts (fans or compressors), but the one big capacitor on secondary side is for 400 V which would suggest 230 V. Input is 35 V/4700 uF, thats OK for 24 V, we are in car, the voltage fluctuates really.

(I know that while lead/sulfur acid battery is labeled 12 V, when fully charged its voltage is as high as 12,8 V, which means 25,6 V here. But for charging you actually use some 14,5 V (so this must go from generator, right?) so it is some 29 V here. You cant run such bloody thing from the battery;-) Not more than for 5 minutes.)

[budm]

Re: Interesting stuff - truck air conditioner unit board

That was the first thing I searched for, replacement compressor. The unit is advertised as a 24V compressor system, Operating range is 20~30VDC, 12~22A.

Must be made for big truck that runs on 24V system.

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

Yep, it is from unit in truck brother which operates. However, as I said, due to the price and the fact ALL trucks in the company have the unit inoperational, they don't want to replace it. And brother won't buy board into somebody elses truck, right? So if I can repair it for fraction of its price;-)

It operates on 24 V, yes, but from diagrams, the compressor seems like ordinary compressor you find in fridge! And I see no point in running this thing on low voltage - insane looses with currents in 10 A range. Together with the fact there is high-voltage cap on secondary, I think it is really step-up for ~230 V, at least for the compressor, fans could operate on either 12 or 24 V.

[budm]

Re: Interesting stuff - truck air conditioner unit board

If you can get to look at how many wires are from the compressor then it may help identifying the type of motor is used for the compressor, it also should have tag on the compressor itself. 24V single phase is not efficiency, multi-phase DC is more efficiency and they can electronically control the speed with the amount of load requirement so it will not put heavy drain on the truck power system.
If you can fix one, more likely the other will have the same failure mode, then your brother cam save a lot of money and you may be able to offer repair service to other truck owners as well. Troubleshooting the first one will be difficult, but once you figure it out, then it will be easy from then on.

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

Yep, I know, thats the second thing Well, from what he told me, different company had similar problem, many boards were damaged, one heavily coroded, one even broken in half, only one unit beyond repair. I can get contact to one guy who did it in this second firm, but the gus is supposedly "busy and stuff", you know how it works

I can only try to access brothers truck which he has on parking lot during weekend, than nothing. I asked him for that too, first thought I may find some info on web, but obviously there is nothing and I will have to look at that

[b700029]

Re: Interesting stuff - truck air conditioner unit board

Looks like a 2-sided board with nice big traces, so it shouldn't be hard at all to trace it and derive a schematic, then figure out how it's supposed to work.

Post clear directly-overhead pictures of the front and back if you'd like some help

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

Sure, in my lab, I have also some photo stuff there, including good light and white surface

[davg]

Re: Interesting stuff - truck air conditioner unit board

Might check the board for cold solder joints?? I have seen this in several boards on Honda and GM products.

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

OK, finally got to it. What I found so far is one shorted transistor - IRF1010N - on the input side. That would explain the blown fuse.

IRF3205 seems to be more than good substitue. Only thing I do not know is the fuse I should use. I can simulate 24 V with two lead UPS batteries, hopefully if it would work without the panel I will see what voltages come from it. I think I can be safe with regular 6,3A fuse for the time being, since there is no output really it should not consume much power.

ADD// as for the topology side, output is definitelly high-voltage, than it goes to the collector (most likely, but central pin :-)) of single transistor in every of the three couples. Every couple is driven by IR2104 half-bridge driver. My guess is it is there to simulate sine-wave, whaddaya think?

[ben7]

Re: Interesting stuff - truck air conditioner unit board

OK, finally got to it. What I found so far is one shorted transistor - IRF1010N - on the input side. That would explain the blown fuse.

IRF3205 seems to be more than good substitue. Only thing I do not know is the fuse I should use. I can simulate 24 V with two lead UPS batteries, hopefully if it would work without the panel I will see what voltages come from it. I think I can be safe with regular 6,3A fuse for the time being, since there is no output really it should not consume much power.

ADD// as for the topology side, output is definitelly high-voltage, than it goes to the collector (most likely, but central pin :-)) of single transistor in every of the three couples. Every couple is driven by IR2104 half-bridge driver. My guess is it is there to simulate sine-wave, whaddaya think?

I say you should give it a go

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

Brother informed me there used to be a 30A fuse, so I bought some for testing :-D (this stuff is pretty cheap compared to for example glass fuses!) Also got the transistors so I can give it a try, yes. Gonna have a nap for it and play with that during night after some sleep, just for case

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

OK, got some nice sparks and one dead 30A fuse Not sure what to do next, nothing seems to be wrong in there from my point of view. The problem should be on the primary side as being on secondary, it would just blow things there. But all the IRG4BC20KDs (IGBT) are fine.

Well, there is also one slightly burned component which seems to be SMD resistor. It actually looked good before I touched it, than the top layer with printings just dropped of I remember there was something like 162, maybe 1R2 or 1k2? It reads some 1130 ohms…it is between the two primary transistor gates like: gate-SMD cap-resistor-gate

[ben7]

Re: Interesting stuff - truck air conditioner unit board

OK, got some nice sparks and one dead 30A fuse Not sure what to do next, nothing seems to be wrong in there from my point of view. The problem should be on the primary side as being on secondary, it would just blow things there. But all the IRG4BC20KDs (IGBT) are fine.

Well, there is also one slightly burned component which seems to be SMD resistor. It actually looked good before I touched it, than the top layer with printings just dropped of I remember there was something like 162, maybe 1R2 or 1k2? It reads some 1130 ohms…it is between the two primary transistor gates like: gate-SMD cap-resistor-gate

Probably a mosfet driver chip has gone bad also.

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

There are two, TL494 and "258 EZ621" from ST Micro. Actually, there are some paths going all the way arround the rim to the part with more SMD components. There are two more EZ261 and lots of other stuff.

The thing is, if something from this would be shorted, do you think it can blow of 30A fuse without melting the paths? :P I think it is something more major, but can't find it though…

[ben7]

Re: Interesting stuff - truck air conditioner unit board

There are two, TL494 and "258 EZ621" from ST Micro. Actually, there are some paths going all the way arround the rim to the part with more SMD components. There are two more EZ261 and lots of other stuff.

The thing is, if something from this would be shorted, do you think it can blow of 30A fuse without melting the paths? :P I think it is something more major, but can't find it though…

If you were to apply 30A for a long time, the traces would begin to melt and smoke.

But, they can handle a surge current to some degree.

Take all the mosfets out and see if it still blows the fuse.

If it doesn't, with the mosfets still out, check the gate connections on the circuitboard for shorts to +V and/or ground.

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

Can do it, yeah. Will try first with the TO-92 and than proceed with others if it will continue to blow (there are some SMD transistors for DC-DC, low voltage for fans and controll boards I think).

Well, just that after replacing the one transistor, there are no shorts any longer even with having them in, so I thought there won't be any with transistors mounted

Just about the smoke and melting…you know what lead batteries can do, you can solder with them I bet the spike was much greater than just 30 A

[Behemot]

Re: Interesting stuff - truck air conditioner unit board

OK, it is still blowing fuse after unsoldering primary transistors.

But here is the deal. I have been thin king about the diode (the huge one) which is on input side, just after fuse. Can it really work with diode being in conducting state between voltage and ground? Shouldn't the diode be, like a, in opposite state to block half of the AC when it would accidentally be applied?

It should, right? So, how big idiot am I to solder it in like that? Tell me please…