How do we know if the exp. valv. is bad, or not working rt. on our a/c units??? Mine acts like it gets to the exp-valv block !!! but know cool air, Do es the exp-valv have a by-pass in it, there are bubbles in the glass, but low side hose don't get cold, hi-side don't get hot to touch, am i blocked???

 

bubbles in the glass means low on refrigerant

that is your problem

and not positive but it likely doesn't have a tx valve
most likely a mtering oriffice

 

Lucas, thanks for come back. I for got this is a 91.5 d250, po put in new comp., ( had someone put it in) I'm using a retro kit to add freon 134-and even w/ 1-1/2 cans still no cool air just thought i might be blocked some where. Don't think they pulled a vac. It was wired direct to comp when i bought it i did the the by pass to the therm., sw, can't see name on comp ( o' reily i think???) followed ins in kit gauge read 45-55 lb, good to 85+ out side temp ---- still no cool air????? That's why i wondered if it was just circulating at the expasion valve???

 

Unless it was changed, it probably had r-12 in it. Also, usually, The filter-dryer and sometimes the expansion valve needs to be replaced when the compressor is replaced. Did it ever blow cold after the comp was replaced? New compressors come with labels to indicate whether it is r-12 or r-134A, because the compressor is the same. The oil and the seals are incompatible between R-12 and R-134A. If the filter-dryer or expansion valver is not replaced, it voids the warranty (usually). Also, if the other compressor failed catastophically, it can contaminate the entire system, which then needs to be flushed and cleaned real well...

 

Hey, maybe, the air has never blown cold, since i bought the trk., the whole rig only has 2650 miles since it was rebuilt from frt., to back.!!!The low pressure line would turn white w/ frost ,but no cold air has ever came out, like i said they wired the comp., direct. I unhooked the wireing, until i knew i would have time to work on it-----well ---it's time, sounds like a rebuild, but it does have a new dryer ,and tomorrow i'll get a new evap., valve& start from there, thanks again.

 

I would just get a new Expansion valve and receiver drier, there cheap, Might want to see if the evap core is plugged up too.

 

Great, don't forget to flush it out and pump it down before you try to charge it. It sounds like there maybe a blockage somewhere in the system. They really aren't that complicated. Here is a cheapy from Harbor freight...Mark

 

dont start throwing money at it




first get a real set of guages and tell us what kind of pressures you have
what the system is (converted) or not
what the compressor name plate says



it would be cheaper and less time consuming to take it to someone with the right equipment


are you going to reclaim the gas you have in there?
evacuate the system?
purge and leak check with nitrogen?



i dont usually see bad expansion valves

 

Well, guys i pulled the unit apart blowed through condsen., all the lines through the evaparator, put in new expan-valve,pulled 40 min vac., 29., let sit another 40 min., did'nt loose 1 lb, also sprayed soap / water on all fittings no leaks !!!! Pulled blue gauge to 55 lb. rede to 225-250(head pressure) so after running 45min-1hr it's hot enough in the cab to bake cookies#@##@#%%%& no cold air???? Used almost 3 cans of 134(aprox., 32-36oz) man do wonders never cease.

 

Did you check the evaporator under the dash? It could be full of crud in the fins or plugged internally, but more likely the fins...Mark

 

I think I mentioned that once already, Could be a door problem too.

 

Yea, guys i did do the both, washed the evap/ again gust to make sure it's very clean(i did the sq., cut-out back when i 1st., got trk.,) and "pull" i did need to adjust the temp/slide as it wasn't opening fully, what cooling it does do it seems to work better w/ the fan on low/med.