i have a 99 extended cab sb 4x4 superduty 7.3l automatic trans that i am having problems with the air conditioning on it. the symptoms are most of the time it works but some times when i am driving normal it shuts off and starts blowing hot air. if i floor it for a sec and get the rpm's above 2500 it will turn back on and work fine for a few minutes then start all over again. if i stop the truck and it is not working i can rev it up and it will turn back on. it will stay on all day if i dont drive it and let it idle, but as soon as i start to drive it acts up again. i have replaced the pressure senser on the high side and i have had it charged and checked for leaks and there are none. the geniouses at midas muffler shop cant seem to tell me any thing after i spent 300 dollars for a "pros" to tell me what is going on. any help would be apreaciated. thanks josh
99 powerstroke air conditioning problems
- Thread starter pineman69
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oi8228oi
another 99
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im not an ac guy and wont pretend to be but it sounds like it might be your compresson is going out.
also when you get time you should give us a signature and let us know about your truck and mods... also is it a 99 or a 99.5 (if ya got a door badge instead of a fender badge its probably a 99.5)
CHPMustang
Senior Member
Welcome aboard there Josh
If the pressure is up and there's no leaks located I'd have to assume with some certainty that the Fixed Orifice Tube might be clogged but not 100% sure until it gets removed for inspection.
An alternative to the stock orifice tube is the Variable Orofice Valve which I'm yet to do on our truck
here's a LINKY
If the pressure is up and there's no leaks located I'd have to assume with some certainty that the Fixed Orifice Tube might be clogged but not 100% sure until it gets removed for inspection.
An alternative to the stock orifice tube is the Variable Orofice Valve which I'm yet to do on our truck
here's a LINKY
Big K
SDD.com Hacker/Admin
Also, more on that Smart VOV Tube,
I just picked one up the other day and hoping to put it in this weekend.
I found a cross reference # for O'Reilly's Autoparts.
it is #38902, List is $19.99.
I will let yall know how it goes once I get everything in.
Just fyi
I just picked one up the other day and hoping to put it in this weekend.
I found a cross reference # for O'Reilly's Autoparts.
it is #38902, List is $19.99.
I will let yall know how it goes once I get everything in.
Just fyi
powerboatr
living well in Texas
I would third the orifice tube, sounds like its stuck up with debris.
however, if you paid em 300 to diagnose and fix it, take it back and have em throw the gauges on it, watch the low and high pressures, if its jumping all around then you got a restriction acting like a check valve of sorts.
thats the easiest and fastes way to check.
The Suction pressure (Low side)is a reflection of how well the evaporator portion is picking up heat and how well the compressor is removing it . The Head pressure is a reflection of how well the condensing coil is getting rid of the heat and how much load the system is putting on it (higher). idealy a high or low pressure is a good thing depending on what is causing it. In general you want the suction pressure to be as high as possible without it being caused by an over charged condition and the head pressure to be as low as possible but high enough to change gas back to a liquid..
if i remeber right ford says a low side of 44-35 is good. last run on mine was 37,
sorry about the typos its a bad hand day for arthritis -mad
if some on ehas the cd they may be able to post the ford rec. pressure vs temps.
however, if you paid em 300 to diagnose and fix it, take it back and have em throw the gauges on it, watch the low and high pressures, if its jumping all around then you got a restriction acting like a check valve of sorts.
thats the easiest and fastes way to check.
The Suction pressure (Low side)is a reflection of how well the evaporator portion is picking up heat and how well the compressor is removing it . The Head pressure is a reflection of how well the condensing coil is getting rid of the heat and how much load the system is putting on it (higher). idealy a high or low pressure is a good thing depending on what is causing it. In general you want the suction pressure to be as high as possible without it being caused by an over charged condition and the head pressure to be as low as possible but high enough to change gas back to a liquid..
if i remeber right ford says a low side of 44-35 is good. last run on mine was 37,
sorry about the typos its a bad hand day for arthritis -mad
if some on ehas the cd they may be able to post the ford rec. pressure vs temps.
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bartman
Full Access Member
I'm subscribing because I have the same issue. I put gauges on it and both sides were low, indicating a low charge from what I understand. I added a can and didn't notice much difference in behavior. I believe that I have enough refrigerant, and it will freeze you out most of the time, but then there are those occasions that it will blow hot and i have to do the gas trick above to get it going again. In order to see spikes and whatnot while the problem is occuring, I'd have to drive around with the gauges in place, and that is not possible. I just want reliable A/C.
powerboatr
living well in Texas
BARTMAN
if thats the case and you added a can...
i would follow the line of "for the age of your truck i would spend the $$ to have it evaced and refilled." if you have low high sides say less than 120 your in need of professional servicing equipment , and change teh orifice while your at it.
if thats the case and you added a can...
i would follow the line of "for the age of your truck i would spend the $$ to have it evaced and refilled." if you have low high sides say less than 120 your in need of professional servicing equipment , and change teh orifice while your at it.
bartman
Full Access Member
my low side was 29-35 and the high's were at 175 (IIRC) and that was at 90* F ambient. Low from the documentation that I have seen.
powerboatr
living well in Texas
bartman said:
yep you got issues,
i got my psd to 37 once on the low, 45 is optimal IIRC
but your 175 high is a bit low,
i am not sure what $$ are there for an evac but i bet its about 150 buckaroos for time and equip. a bit steep but,.....
bartman
Full Access Member
Steep, but if $150 and the smart VOV get me 
then I am willing to pay.
then I am willing to pay.