Going to be vacuuming down my ac system soon ... And then recharge ... Any hints ?? Have the gear but not done before ,... ;)

Not 40 as it cycles, but a CONSTANT 40psi when running. At an idle it should not be cycling much if at all. Far as things going boom, look down by the compressor and you will see a pressure switch. That pressure switch is there just in case the pressure goes over about 250psi and shuts the compressor down. The high side can very easily handle 300+psi.

Cool guys ...... I really want to get this fixed ....... mainly cause I live in PHX and also cause I already paid $1100 and still have warm air - so don't want to take to anyone now.

thx for help

The relief will pop before anything goes boom. The entire system is designed to handle more pressure than whatever the relief valve is set at which I would guess to be 250-300 psi. The low side should and will go down as the compressor runs as the high side rises, when it sits turned off they will be near equal. when it cycles the low side pressure switch is what cycles it as the high side pressure switch is designed for a safety kick out. What will cause a boom is putting liquid freon in the high pressure side of the manifold with the ac running. When charging only charge thru the low side manifold "Blue" with freon can uprite.

thanksWe should add some of that stuff to the AC link mike wrote when he did his system.Like safe pressures (low and high). And SOAP trick and fan etc and as long as you fill via low side the pressures should be ok. Whatever wording is best Definately wanna get this one to bed. So I will get her loaded again and clean around all suspect places .... then I am going to try and drive and keep the AC running full tilt for 2 hours - instead of the 10 minutes to/from work ..... see where I am at with UV first followed by SOAP/water keep ya posted ....

Here is another site that has good info for you that explains a lot: http://www.aircondition.com/tech/questions/82/

With regards to the high pressure switch, quote from the 2001 FSM A/C Specifications:High psi Control switch - opens > 450- 490 psi, resets <270 - 330 psiAt 80 deg I saw pressures going north of 350 psi on the high side until I put a fan (furnace blower) in front of the condenser. Also noticed as the high side got way up there the low side came up some too. Also, don't think you want to add liquid to the low side (can up side down).Joe in St Louis

Thanks for the specs. I didn't have a book so I was just guessing at the high side pressure switch specs. :duh:Yeah you are right I typed it out wrong and corrected it. To much high and low side typing got mixed up. Great catch.

Thanks guys will post shortly ....

--- Update to the previous post...

Thanks guys will post shortly ....

ok - refilled and it settled around 30 psi and 190 psi.

off to pick up some more r134a

Curious about the SOAP idea - I added some soap bubbles to each Low valve High Valve port - to see if leaking - but problem is with engine vibrating and FAN ..... it doesn't last long and hard to determine if there's a leak or bubbles just getting destroyed by vibration/air from fan ??

The soap method is for an empty system that pumped up with air or nitrogen pressure and not running. Just like putting a tire in a tub looking for an air leak.

The soap method is for an empty system that pumped up with air or nitrogen pressure and not running. Just like putting a tire in a tub looking for an air leak.

doh so you mean even with engine and AC not running - as it balances and holds say 70psi each side ..... still enough pressure to find leak ......

doh so you mean even with engine and AC not running - as it balances and holds say 70psi each side ..... still enough pressure to find leak ......

Its possible but doubtful, if the leak was bad enough to find in the static form you would have found it a long time ago with a black light and it would have been low within a couple days rather than a week. You need to get the low side pressured up into the range of the high side when running as this is the area you most likely will find the leak and static pressure of 70 psi isn't enough to detect it on that slow of a leak. The only way to do it is to empty the freon and pressurize the entire system to a set pressure with air or nitrogen.

Its possible but doubtful, if the leak was bad enough to find in the static form you would have found it a long time ago with a black light and it would have been low within a couple days rather than a week. You need to get the low side pressured up into the range of the high side when running as this is the area you most likely will find the leak and static pressure of 70 psi isn't enough to detect it on that slow of a leak. The only way to do it is to empty the freon and pressurize the entire system to a set pressure with air or nitrogen.

ok got ya man this sucks ........... where is it leaking ....:banghead:

ok got ya man this sucks ........... where is it leaking ....:banghead:

well ---- have blacklighted it 3 nights in row - trying to find leak ...... and definately losing freon as the compressor is cylcing more and the temps aren;t as cold. Really don't want to add fixaleak ..... so here's what I am thinking Have new evap/heater core and high pressure line So leak should be in Low line condensor or compressor Can't see anything on condensor/dryer See a little out of LOW schraeder valve ..... but hard to tell if thats from guage coupling .... Don't see anything out of compressor - but thats where there was supposedly a leak before ISX looked at it ... So thinking of replacing the LOW side line ........ its the only place I can see UV dye (althugh I am 60% sure its not leaking and its from the coupling of putting guages on/off). What you think and where's a good place to get LOW pressure side line .... ?? thx

Well a few weeks ago I noticed my a/c wasn't working so I shot some freon in her! I let it set for a lil while, while I was letting it set I left! My brother called me and said that the low side line was leaking! So I ordered a new manifold line set! Got them in and was getting ready to start installing, an I noticed that the low pressure switch was a little loose! I tightened it up and pulled a vacuum! It wasn't leaking any more! Just a thought!!!

Like what I did was added a dye pack to it. Then using compressed air charged the system to about 80 PSI which is enough to cycle the compressor. Run it for a short time 1-2 minutes to cycle the dye through and shut off. Then get out a black light and look. In both cases now no dye is visable in the engine area. So this means the evaporator is the cause of the leak... Thank goodness NAPA has a lifetime warranty on the evaporator...

Like what I did was added a dye pack to it. Then using compressed air charged the system to about 80 PSI which is enough to cycle the compressor. Run it for a short time 1-2 minutes to cycle the dye through and shut off. Then get out a black light and look.

In both cases now no dye is visable in the engine area. So this means the evaporator is the cause of the leak... Thank goodness NAPA has a lifetime warranty on the evaporator...

Is there a fitting you can make to attach an air compressor to the system ? Assume you charge it on low side same as adding freon ?

Hoping/assuming its not the evaporator - its new - but system has been leaking since it was installed.

--- Update to the previous post...

Well a few weeks ago I noticed my a/c wasn't working so I shot some freon in her! I let it set for a lil while, while I was letting it set I left! My brother called me and said that the low side line was leaking! So I ordered a new manifold line set! Got them in and was getting ready to start installing, an I noticed that the low pressure switch was a little loose! I tightened it up and pulled a vacuum! It wasn't leaking any more! Just a thought!!!

so do u think it was the switch or the new lines ? And where did u get you lines from ? and cost ?

thx

Sounds to me like either the evap leaks or the connections to it are leaking since you said it started leaking when the new evap went in.l

Sounds to me like either the evap leaks or the connections to it are leaking since you said it started leaking when the new evap went in.l

Yeah no its a new EVAP/Heater Core ........it was already broken/warm air => that was the last thing I was charged $1100 for and when it blowed hot air after 3 days I said enough is enough and decided to do all my own work from that point - or to find a local cummins guy/forum friend or shop that I trusted - no more dealers or generic mechanics. So I vaccumed it back down as we had a trip to vegas. So I figured 2 new cans full and 5 hours each way with the A.C on would help - as when I drive to and from work its only 15-20 mins - so hard for compressor and system to get fully worked. So for the 1st time I have noticed some dye comming out of the low pressure line. I had not seen it before as there was always a little dye on both HIGH and LOW valves as you disconnect the coupling from filling with freon - just a small amount. Anyway I will get some pics uploaded soon. The way I know its new DYE is I CLEANED all the terminals and caps after filling to ensure NO/LITTLE dye - and now I have a good ring on the valve. So couple questions. 1) Where's a good place to pick up a LOW side line only. Price ? 2) I was wanting to vacuum down ...... and refill - and then plug the low side VALVE with something that would form a seal, but could be removed cleanly if I needed. This way I can test if this is truly leaking prior to changing the line. Any ideas of what I could use ?? I was thinking something like a waterproof "cauking" or whatever .... so a) Vacuum down b) Refill till holds 30+PSI c) Fill will caulk d) monitor/evaluate. If I determine this wasn't the issue - I can carefully remove the caulking from the valve ..... thoughts on both (1)+(2) ?? thx guys will post pics soon:thumb1:

On my truck it was the the switch on the low pressure line that was leaking! I tightened the fitting and don't have the issue any more with the leak! I have the lines that come off the back of the compressor for high and low side part number 4811770, I gave $ 75.00 for them. All the part stores can get them varying in price from $139.99 to over $250 at the dealer! If you need or want these lines I'll take my $75 plus shipping costs for them! I'm always looking for good deals myself!

On my truck it was the the switch on the low pressure line that was leaking! I tightened the fitting and don't have the issue any more with the leak! I have the lines that come off the back of the compressor for high and low side part number 4811770, I gave $ 75.00 for them. All the part stores can get them varying in price from $139.99 to over $250 at the dealer! If you need or want these lines I'll take my $75 plus shipping costs for them! I'm always looking for good deals myself!

The low side switch is down near the compressor right ? Only part I don't get is if it was leaking shouldn't you pick up some dye ?? Will check it tho - so thanks for tip. Let me get back to you on the line - don't suppose you wan to sell just the low side - as I have a NEW high side - but thanks for the lead - I wanna see if I can plug it first and see what happens to my vacuum and AC. Couldn't find that part number on the couple sites I checked ....... hoping this is it .......

The low side switch is down near the compressor right ? Only part I don't get is if it was leaking shouldn't you pick up some dye ?? Will check it tho - so thanks for tip. Let me get back to you on the line - don't suppose you wan to sell just the low side - as I have a NEW high side - but thanks for the lead - I wanna see if I can plug it first and see what happens to my vacuum and AC. Couldn't find that part number on the couple sites I checked ....... hoping this is it .......

Yes sir the switch is on the line near the compressor. The lines that I are the ones that come off the back of the compressor! Which line are you thinking that you might need?