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Old 05-28-2011, 07:41 AM   #16
j cAT
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Re: 98 Suburban a/c pressure -30 low-155 high

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What is the proper way to check an evaporator or condenser for partial blockage after removing them?
Thanks!
as mt2500 stated measuring the temperature across the condenser surface for a sudden change in temp,,, this would be where the clog IF ANY is............


since your vehicle did have much higher pressures on the high side when / prior to your recent work the 155psi is not good with the temps you now have at your reported location..

how much R-134 did you install into this system ?
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Old 05-29-2011, 03:08 PM   #17
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Re: 98 Suburban a/c pressure -30 low-155 high

Right now it's 94 degrees outside and I'm getting:
idle 55/175
1500 rpm 43/200
200 rpm 40/225 ( this might look fairly good but not for this vehicle)

vent temp at high is 65 degrees. It's alway 30 degree less than outside temp. I drove 300 miles yesterday on the highway without variation.


I have a great electric fan as well as the factory equipment. This truck cools very well under tough conditions.

static pressure is 80, up from cooler temps a couple weeks ago.

This truck would pull 28/325 in 100 degrees with vent temps in the low 30's on low volume, with rear ac off. Rear ac would pull it up 5 degrees or so.


I have a laser thermometer that doesnt reveal any restriction in the condenser. I had it out and blew air thru it, it seemed fine but I imagine thats not a real test.

I have four 1/4 pounds of r-134. Thats a 1/4 over I added to see if it would help, of course it did not.

No leaks, I havent looked at the evaporator, its tough to access. I wonder if something built a nest in there, but there is no outside evidence and the blower volume seems fine.


Thanks again, I dont have a recovery unit or I would go through it again. I'm looking to get a slightly used one today.
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Old 05-29-2011, 03:44 PM   #18
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Re: 98 Suburban a/c pressure -30 low-155 high

Quote:
Originally Posted by cris2004 View Post
Right now it's 94 degrees outside and I'm getting:
idle 55/175
1500 rpm 43/200
200 rpm 40/225 ( this might look fairly good but not for this vehicle)

vent temp at high is 65 degrees. It's alway 30 degree less than outside temp. I drove 300 miles yesterday on the highway without variation.


I have a great electric fan as well as the factory equipment. This truck cools very well under tough conditions.

static pressure is 80, up from cooler temps a couple weeks ago.

This truck would pull 28/325 in 100 degrees with vent temps in the low 30's on low volume, with rear ac off. Rear ac would pull it up 5 degrees or so.


I have a laser thermometer that doesnt reveal any restriction in the condenser. I had it out and blew air thru it, it seemed fine but I imagine thats not a real test.

I have four 1/4 pounds of r-134. Thats a 1/4 over I added to see if it would help, of course it did not.

No leaks, I havent looked at the evaporator, its tough to access. I wonder if something built a nest in there, but there is no outside evidence and the blower volume seems fine.


Thanks again, I dont have a recovery unit or I would go through it again. I'm looking to get a slightly used one today.
Thanks!
Could be low charge or weak compressor or orfice tube/expansion valve bypass.
I would pump it out and vacumn it deown and add the set charge and see what it does.
Let us know how it goes.
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Old 05-29-2011, 03:47 PM   #19
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Re: 98 Suburban a/c pressure -30 low-155 high

How much R-134a are you putting in it for a set charge.
Are you using a vacumn pump to pump it down?
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Old 05-29-2011, 05:02 PM   #20
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Re: 98 Suburban a/c pressure -30 low-155 high

I pulled -28 overnight before re-charging. Twice lol.
I don't know what you mean by a 'set' charge, please explain the phrase.
I first changed the compressor to a four seasons, didnt fix it of course, and then replaced with another new delco unit, tube and dryer while having the same problem.

Additionally, I had a leak in the high side port shortly after, so I checked the condensor while it was empty of freon again, vaaced it and recharged onlt to have the same problem.
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Old 05-29-2011, 05:50 PM   #21
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Re: 98 Suburban a/c pressure -30 low-155 high

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I pulled -28 overnight before re-charging. Twice lol.
I don't know what you mean by a 'set' charge, please explain the phrase.
I first changed the compressor to a four seasons, didnt fix it of course, and then replaced with another new delco unit, tube and dryer while having the same problem.

Additionally, I had a leak in the high side port shortly after, so I checked the condensor while it was empty of freon again, vaaced it and recharged onlt to have the same problem.
Set charge is the amount of R-134a the system calls for.
Like on the ac information sticker on dryer.

How much did you put in it when you recharged it?
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Old 05-29-2011, 07:02 PM   #22
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Re: 98 Suburban a/c pressure -30 low-155 high

It calls for 4 pounds, I have 4.25 in it now. I worked up slowly, added the quarter more thinking I may be off, didnt get any better of course
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Old 05-29-2011, 07:37 PM   #23
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Re: 98 Suburban a/c pressure -30 low-155 high

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It calls for 4 pounds, I have 4.25 in it now. I worked up slowly, added the quarter more thinking I may be off, didnt get any better of course
your evap could very well be dirty...a rodent nest etc...

with replacing the compressor and having the correct charge you should have much higher pressures IF the evap can absorb the heat.....

since the compressor change did not change anything this should be investigated..

when I would check out much larger ac units with multivalves I would get the interior vehicle temp up to 100 degf , then block off the condenser cooling by using some cardboard...

I could determine if it was low on refrigerent or a valve problem...

the pressures needed to be high and if so I knew the compressor had all cylinders working..

if the pressure rise was too slow then I knew the charge was low, also I had a glass to indicate this but still this confirmed low charge condition..
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Old 05-29-2011, 09:08 PM   #24
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Re: 98 Suburban a/c pressure -30 low-155 high

I seem to get slightly better cooling temps with rear only on. If it was the evap in in the front I'd expect rear performance to be better. None the less, I have no where else to look!
I've been trying to locate the drain for the forward evap condensation, seems there was a plastic tube before. I'm not getting any drainage at all, though its is 10-15 percent humidity now. It appears the dash has to come out to get at the evaporter, so I'll take a few things apart to see if I can get a look.

I guess if it's not expanding properly in the evap, it cant be compressed later.
This has been very frustrating to say the least.

I appreciate the help.
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Old 04-21-2016, 04:08 PM   #25
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Re: 98 Suburban a/c pressure -30 low-155 high

Any final answer to this puzzle?
My guess orifice tube in backwards.
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Old 04-22-2016, 12:59 PM   #26
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Re: 98 Suburban a/c pressure -30 low-155 high

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Any final answer to this puzzle?
My guess orifice tube in backwards.
Post is 5 year old!!!!!
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Old 04-22-2016, 03:55 PM   #27
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Re: 98 Suburban a/c pressure -30 low-155 high

So 5 years later I read the thread and get to the end and find no cause of the problem and wonder what could the final answer to the question be?
And you tell me the thread is 5 years old. Well that wasn't my question and I do see " 05-28-2011, 06:41 AM"
So what's your point? How to engage in wasting time responding to useless comments about legitimate questions.
Denying the question doesn't make it go away.
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Old 04-22-2016, 06:42 PM   #28
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Re: 98 Suburban a/c pressure -30 low-155 high

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So 5 years later I read the thread and get to the end and find no cause of the problem and wonder what could the final answer to the question be?
And you tell me the thread is 5 years old. Well that wasn't my question and I do see " 05-28-2011, 06:41 AM"
So what's your point? How to engage in wasting time responding to useless comments about legitimate questions.
Denying the question doesn't make it go away.
YOU being new to the forum , many people use this to get ideas to their vehicle failures then they disappear most times forever . very typical of members that just join to get the answer or ideas to find a fix or even to investigate if some dealership most time that F'ed them.

asking about what happened on a posting 5 yrs old is st...d......
sorry if your offended but , it is what it is..

you got some vehicle problem make your own post and give vehicle details and what troubleshooting you did so far .

good luck .
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Old 09-19-2017, 02:15 PM   #29
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Unhappy Re: 98 Suburban a/c pressure -30 low-155 high

Hey j Cat,

I am ashamed to say I did disappear after all the great help I got here!
I lost the transmission, had a multitude of problems catch up the vehicle, got busy with life and work and parked the truck until a few months ago.

I have gone through and refreshed everything else, but the AC is still not fixed!
After sitting a years the ac is exactly the same after adding a half pound of Freon.
Cooling is so-so in the back, not at all in the front, pulling 40/200 at 95 degrees.

I am about to pull it all apart and flush it out, starting over. I'll start at the orifice tube since the expansion valve in back works. If it is backwards I will confess to it!

Thanks to all
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