RE: Prostar ac

[Rawze]

(06-30-2019 )Daytripper Wrote:  Low side drops to 20-25 while compressor cycles. The high side is at 140-150 till compressor cycles off then climbs to 340 at which time the compressor kicks back on and fan engages...

20-25 is very cold. enough to cause the system to freeze up. Mine ruins about 35~ish most of the time.

high side pressure goes up when compressor is ON,.. not OFF. -- 340 is normal for the high side to kick out and fan to come on.

[DosGatos]

On my 2011 prostar 871, the air temp probe under the radiator goes to the ecm for part of the idle control. nothing to do with the ac.

[Rawze]

(06-30-2019 )DosGatos Wrote:  On my 2011 prostar 871, the air temp probe under the radiator goes to the ecm for part of the idle control. nothing to do with the ac.

it is my understanding that the cab controller also reads it from the engine via J1939 and uses it to compare to the thermistors on passenger side of truck, then pass/fail the thermistors. <-- lovely wonderful garbage programming meant to keep you guessing what is wrong.

in all actuality, the mechanical parts of the system is no less robust than anything else out there... condenser is decent, compressor is decent, air dryer/ accumulator is decent, expansion valve is decent,.. piping and hoses are ok,,.. it is only the electronics (mostly programming logic and over-bearing, unnecessary sensors) that keep the system with constant problems. - Likely some jerk-off in a 3rd world country making $2.35/day programmed it, never had to sit in one in the middle of the desert before.

The only mechanical problems really they have are the blend doors not sealing as they get old (warmer than normal A/C, barely gets cold) and the blend door motors not being able to actuate them properly / breaking or hanging up when this happens. it is understandable that the blower motors will wear out eventually, they are typical cheap-o dc motors that could not be expected to last past about 400k miles in a stretch. -- Besides that, neglect of the air filters or not keeping the system clean are its enemy too.

[Rawze]

when my truck was brand spanking new, the A/C system works without question,.. had absolutely no issues and worked no matter what.

the one time I took the truck to the stealershit to have the speed limiter removed (before i had my own copy of insite) and have the EGR cooler replaced because it was seeping and had warranty,.. when i got the truck back, they claimed they updated the cab controller software(this was in 2010). -- ever since that day,.. the A/C never worked even half way right again. -- i demanded they put back the old software in the cab controller,.. they claimed they were not allowed to.. -- i fought that A/C system for a couple years or more, keeping it going against the cab-controllers complaints before eventually resorting to making my own controller for it,. and it has run pretty much flawlessly ever since.

[DosGatos]

(06-30-2019 )Rawze Wrote:  it is my understanding that the cab controller also reads it from the engine via J1939 and uses it to compare to the thermistors on passenger side of truck, then pass/fail the thermistors. <-- lovely wonderful garbage programming meant to keep you guessing what is wrong.

Thanks, I couldn't see the magic smoke peering at the wiring schematic.

[Rawze]

(06-30-2019 )DosGatos Wrote:  

(06-30-2019 )Rawze Wrote:  it is my understanding that the cab controller also reads it from the engine via J1939 and uses it to compare to the thermistors on passenger side of truck, then pass/fail the thermistors. <-- lovely wonderful garbage programming meant to keep you guessing what is wrong.

Thanks, I couldn't see the magic smoke peering at the wiring schematic.

It really is ridiculous what they have done with the A/C programming. They even try to use the day/night sensor in the top of the dash (that tiny little black dot looking sensor thing that every driver seems to cover over with their log-book or these days,.. bag of cheeto's,.. right above the steering-wheel, -- that thing is for detecting "fog conditions" and all sorts of other over-bearing horse-s$it in that cab controller.

[Rawze]

Someone on phone yesterday was asking me same stuff as mentioned on here,.. they also started asking how to force it to work. I thought i would mention this, as it is likely someone's next question...

The A/C on the prostar, here is the basics of what you can and cannot get away with, believe me, I learned this the hard way playing with mine...


Besides ensuring the mechanical parts of the system are working and are in good health,.. including blend doors, etc (the place to always start when servicing A/C) ...


Method(s) for helping the factory cab-controller to be "more happy" and not fault out the A/C so much ...

* Making sure the Ambient temp sensor for the engine is reading OUTSIDE TEMPS and not 10+ or even 30+ degrees higher because it is mounted under the truck or hood somewhere and it reads high due to engine temps.

* Making sure the thermistors on the passenger side of the truck are reading correctly. - Easily done by having a spare (known good) sensor and taking an ohm-meter/multimeter and comparing resistance at room temp on them. Making sure they are all reading somewhat same when system is off and they are all same as outside temp. - Really low resistance on one or all of them (like 300 - 500 ohms or less),.. THEY ARE ABSOLUTELY BAD! - I have had some come right out of the box like this from new.

* making sure the condenser and the evap. are working very well. NO dirt of grime in them to slow down air flow or cause efficiency losses. Same with cab filters both front and rear bunk.

* Making sure ALL of the fuses in the dash panel are NOT TARNISHED!..- Same is what is described in this post(s)...
http://rawze.com/forums/showthread.php?t...1#pid12861

* making sure the expansion valve is not plugged up with stop-leak,.. seems everyone these days is stop-leak+dye happy and that is a big killer of A/C on prostar. - The system hates that stuff!. - If you have a leak somewhere-- FIX IT!, and if you can't find you leak,.. PUT A SMALL BALOON that fits tightly OVER THE SERVICE PORTS and wait a while! - YOU WILL FIND YOUR LEAK because 9 of 10 times it is loosing pressure all the time is because of bad schrader valves! - because some moron put a dirty, dusty service tool on it, or did not bother to clean the valves before connecting to them.

* resetting it when it acts up by installing a reset switch like mentioned in this video...
https://youtu.be/flXkmAzsV7E

* LASTLY,.. AND VERY MUCH OVER-LOOKED!!!! --- IS THE FACT THAT PROSTAR IN PARTICULAR --> THE EXHAUST IS VERY CLOSE TO THE UNDERSIDE OF THE CAB--- AND NO PROSTAR COMES FACTORY WITH A FULL EXHAUST WRAP!!!! ---<<<< WRAP THE EXHAUST PIPING ALL THE DOWN ITS LENGTH AND IT WILL BE 10 -20+ DEGREES COOLER IN THE CAB ALL THE TIME!
I have made several mentions of this over the years on here. hers is one of those that came up in a search: http://rawze.com/forums/showthread.php?t...6#pid20496


-------------

Things you cannot do on your own to force it to work...

* You cannot just jumper the compressor. It will make so much pressure, it will blow the guts out of the relief valve or blow apart the compressor. - This will make problems much worse.

* You cannot just jumper the engine fan to have it run non-stop to try to make it cooler,.. this will kill your fuel mileage so badly that you can't make a profit. Keeping the engine fan on at idle to help the A/C along a bit is not a problem though.

* You can't just jumper out the thermistors on the passenger side. The cab controller checks them at intervals to ensure they are changing in value AND that they are within a certain range compared to outside temps. Jumping them out usually makes the system fault out at exactly 10 minutes after the first time the compressor kicks in. I know this because I tried several ways to fool it. - I even resorted to putting resistor bank on a small 12v relay that activates same time as the compressor clutch, so that the resistance changes, .. this fools it some,.. but after a while it figures this out too and faults it anyways.

* you can't just have the compressor clutch tied directly to the high pressure sensor through some control means, based on pressure regulation alone. - Tried this too. - The thing makes cold air, but the damn evap core freezes up all the damn time, and if you bleed the system so that it does not, then as the weather changes, it freezes up any ways. I even tried resorting to modifying the expansion valve to get this to work,.. still a no-go,.. still problems with having to shut it off all the time to let if thaw out after its blowing hot-arsse air out the vents.

* There is however one advantage to controlling the A/C compressor yourself,.. and that is the fact that the blend door and blower motor system IS NOT TIED TO THE CAB CONTROLLER.. it is a completely separate system, located on the circuit board right behind the control knobs. - This means that no matter what you do to the compressor side of things,.. it will not effect the operation of these systems. This also means that if the blower(s) are not working properly,. or the blend doors are not working properly,.. it is NOT a problem in the cab controller.


* What I resorted to, through much experimentation on mine any ways,.. is to ..
-- put a relay on the clutch circuit and control the compressor on my own based on 2 things. They are BOTH the high pressure sensor -- AND-- a separate temp sensor I installed in the evap core to tell me when the system wants to freeze up. I also resorted to manually controlling the engine fan, makng it come on when the pressure gets to above 250-psi or so. This works well to improve its efficiency without too much loss in fuel mileage in engine, as it will rarely ever see that high of pressure when going down the roads above 30 mph or so due to better cooling.

That is what i know about this system,.. and what ? I have done. i resorted to the arduino idea, because I got so sick of mine not working, just like everyone else I have met that owns a prostar. mentioned here:
http://rawze.com/forums/showthread.php?t...2#pid15312

Making an arduino project to bypass the cab controller on the A/C is not recommended unless someone has some programming and electronics background themselves. You have to be willing to chase your own issues with it. No one else will ever be able to work on the A/C system for the truck if you resort to doing something like this ... so it is NOT recommended for the average truck owner/driver.

[Chamberpains]

I don't own a prostar, but is it possible to gut the entire system and put the simple a\c system they used on every truck prior to the prostar?

A simple 12v system with high and low pressure cutout switches and thermostatic control in the evaporator to control freeze ups? It works flawlessly on the predecessors to the prostars.

[Daytripper]

Well one of my thermistors must have been on it's way out(1 month old). Are their any "better" thermistors or should I buy the cheap Chinese ones again? We