greamie

A/C Charge on '02 Freightliner

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greamie   

Cockpit air wasn't real cool. Local tech hooked it up, ran the check, but didn't have info on what the refrigerant charge should be. Someone had printed "2.5" on the unit, under the hood. We assumed that was the charge level. However, while better, air still isn't cold. Any experience out there?

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Is there a sight glass? On our system the tech filled till the bubbles stopped.

Did the tech use a leak detector to check for leaks? These a/c systems are closed systems, so if you're low on refrigerant there's likely a leak. Sometimes they are so small or hidden that it's impossible to find them till things get really bad.

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bm02tj   

With R134 you are over charged if the bubbles are gone 

It needs to be charged with pressure and temperature

or  evac system and recharge  by weight 

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12 hours ago, greamie said:

Cockpit air wasn't real cool. Local tech hooked it up, ran the check, but didn't have info on what the refrigerant charge should be. Someone had printed "2.5" on the unit, under the hood. We assumed that was the charge level. However, while better, air still isn't cold. Any experience out there?

      Sanden equipment is used on allot of the Freightliner chassis.

This is a copy of the Sanden Dash AC diagnostics flow chart  that should help in diagnosing the system. Good diagnostics can save one some major expenses.

  The expansion valve and freeze sensor on this system is located inside the Heater box assembly.  Dirt in the expansion valve area has a detrimental affect on the systems overall performance. 

This repair requires a major disassembly and IS Not something most owners should try. This job requires the proper equipment and supplies. some of it on the pricey side and many areas require the tech to be certified.

Rich.

Note, This information offers some insight into nominal loss of Freon in automotive systems.              

Based on 1000 A/C units opened and recorded by 9 garages in 2000 (three different German car makes), the rate of normal loss is assessed at 6.3 % per year (25% tolerance band) over the first seven years of ex work A/C systems' use phase. Normal loss is considered any refrigerant deficiency of about 40 % compared to the first fill. The losses below 40 % as recorded by the garages are taken as an unintentional sample survey of the normal emissions. The basic assumption is that a 40 % refrigerant loss still allows the A/C system to work just properly. 

Irregular losses are all the losses over 40 %. They are mostly caused by external events like accidents, stone hits and suchlike. Therefore the most defective single circuit component to replace is by far the condenser. The rate of irregular emissions amounts to almost 2 % per year (347 kg from all the 21,300 once a year inspected cars equipped with an R-134a ex-work A/C system).

Future disposal emissions are estimated at 2 %. This is why the assumed 25 % one-off disposal emissions are split into 12-13 usage years of the A/C system.

Thus, the overall emissions range around 10 %/yr. This rate is equivalent to a loss of roughly 88 grams per year and car (average first fill of 0.850 kg). 

 

SANDEN_AC_SYSTEM_DIAGNOSIS_CHART.pdf

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jleamont   

A good mechanic will only use the charge amount as a reference and fill it by the gauge readings on the manifold. I forget what ours calls for but the dealer charged it to that amount, it didn't blow as cold as it should have, I added to it via my gauges, now the pressures are correct and it will freeze you out of the seat.

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I was going to comment last night but didn't. What ever happened to techs that uses gauges to determine head pressure and low side readings to determine the charge?

Richard, I bet yours uses R-22 still, been a long time since seeing the old sight glass on a system. That's right R-22 on most older busses, not R-12, mine was upgraded to 134A before I bought it.

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5 minutes ago, kaypsmith said:

I was going to comment last night but didn't. What ever happened to techs that uses gauges to determine head pressure and low side readings to determine the charge?

Richard, I bet yours uses R-22 still, been a long time since seeing the old sight glass on a system. That's right R-22 on most older busses, not R-12, mine was upgraded to 134A before I bought it.

Correct - OTR (dash) a/c is an r22 system. It was recently upgraded to one of the modern r22 replacements. Both of our basement a/c systems use r12. All three have sight glasses. Oh - the joys of older coaches...

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35 minutes ago, manholt said:

Riichard.

Ditto that.  Way too much high tech today! :P

Circuit boards? We don't need no stinkin' circuit boards!

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If you think things are complicated with r-134a, wait until you have the deal with 1234yf.   

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8 minutes ago, huffypuff said:

If you think things are complicated with r-134a, wait until you have the deal with 1234yf.   

Think you are right. Things are going nuts as the industry looks for the best Freon Mix.

R 410, R 32, R 55 and the list go's on and on . The issue that makes servicing the  system and Freon differences is the operating pressures and temperatures an how they interact with the different ester's. Please give the cooling industry a brake and choose. LOL

Rich.

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1 hour ago, rsbilledwards said:

I am cleaning house, I have a large container of R 12 if any of you with a 12 system needs it.

Were I you Richard, I would send Bill a PM ASAP!

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Both are correct. Our bus a/c is r22, but it's been switched to a modern replacement refrigerant. The two basement units are r12. One has already been switched to a modern refrigerant. The other is still running r12. I will probably need to purge/refill it at the end of this season, so I'll send a PM about the r12.

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9 hours ago, rfsod48 said:

What type of shop works on this system? I have a 2005 FL XC chassis and dash air works poorly.

We've got an Interstate dealer in Milwaukee with a great a/c tech. They work on all makes/models of trucks, buses, and RVs. Best best is to find a shop in your area that services the a/c for one of the local charter bus company's coaches. Next best is a truck repair center with an a/c tech. There should be at least one such place in every major city. I suspect in Michigan you'll find many.

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On 7/13/2018 at 7:28 AM, DickandLois said:

Think you are right. Things are going nuts as the industry looks for the best Freon Mix.

R 410, R 32, R 55 and the list go's on and on . The issue that makes servicing the  system and Freon differences is the operating pressures and temperatures an how they interact with the different ester's. Please give the cooling industry a brake and choose. LOL

Rich.

It's what ever the clean air act 609 wants for the giving time.  In 1995 I had to be certified 609 r-12 and r-134a.  Now I just had to be certified for r-1234yf.  We are not allowed to say freon anymore since 1995, it's refrigerant.  

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