Typos in A/C Service section of Factory Repair Manual?
The factory service manual describes the dual pressure switch (connected to the low side,
I presume?) and the high pressure switch (connected to the high side). If the switches
are not both on, the A/C clutch disengages. In addition, the factory repair manul
describes the normal operating pressures that should be read on a manifold gauge
with the engine running.
Both switches have narrow bands of operation--they turn on at pressure > P1, but turn
off if the pressure > P2 (where P2 > P1). For the high pressure swtich, P1 = 178 and P2 = 220,
and the manual says the manifold high gauge should normally read between 206-213 PSI;
this makes sense since that's in the operating range of the high pressure switch.
However, the low pressure (dual pressure) switch on the low side has P1 = 30 and P2 =33 PSI.
Paradoxically, the manual says the manifold reading should be between 21-28 PSI with
the system running. This doesn't make sense; that entire range is in a range where the
dual pressure switch would shut down the compressor. I checked the other units
(the pressures were also given in SI units) but they were consistent so I couldn't
detect any typo. What's going on here? Someone seems to be smoking crack.
Why are you concerned about pressures? Just add refrigerant until the bubbles in the sight glass dissappear and you're done.
Or, if the system ever became totally empty of refrigerant you need to first replace the receiver-drier, then use a vacuum pump to get rid of system moisture before adding the refrigerant.
This is a '88-'92 forum and all those cars used R12 and have a sight glass built into the receiver-drier to monitor the refrigerant charge via watching the bubbles.
If R134a is used in these cars then the factory manual pressure figures can't be used. Also, R134a will ruin these R12 systems in the long run so it's a downgrade, not an upgrade.
If R134a is used in these cars then the factory manual pressure figures can't be used. Also, R134a will ruin these R12 systems in the long run so it's a downgrade, not an upgrade.
I beg to differ that R134a ruins the A/C system.
If you clean out the oil and flush the system correctly and switch to R134a with a new drier/filter, and (maybe the hoses..) and put in the proper oil for the R134a refrigerant, the system should be fine. Put in any new O-rings that need replacing. Also put the new connectors on on the high and low pressure ports for service.
I am no a/c expert. I am only passing on what is said and known from those that do know what they are doing and the Pros.
Yes, my 1989 Corolla uses R134a.
Last edited by retiredat44; 05-03-2009 at 09:57 AM.
The "Pros" are the snakes that fooled the public into believing R12 would be unavailable and extremely expensive. WRONG!
The "Pros" are the snakes who neglected to tell public "upgrading" to R134a would:
- make the sight glass in the receiver-drier useless so do-it-yourselfers so they could no longer monitor the refrigerant charge unless using gauges.
- make AC outlet temperatures about 5 degrees wamer and make compressor head pressures soar through the roof, deminishing compressor longevity
- make the AC system prone to refrigerant leaks unless special barrier hoses and R134a compatible 0-ring seals
were installed throughout the system - a huge chore and some 0-rings are inaccessible as they are buried underneath the dashboard.
Bottom line: The Pros make big money on R134a conversions and then big money again 1-4 years later fixing
all the problems the R134a causes when it's used in a system originally designed for R12
Kathyricks is right. For anyone who isn't familiar with auto AC refrigerants, R12 is better than R134a in every way except environmental-friendliness. Several years ago, the EPA decided that R12 couldn't be used in new cars in the USA. Retro-fitting is stupidly expensive to do correctly and if you don't do it correctly your AC will probably fail in a few years.
R12 is still available at reasonable prices and a home DIYer should be able to refill a R12 system without much difficulty. If you are worried about the environmental impacts of R12, look into some of the alternatives like OZ-12.
For all the idiots that voted in the loony left envirnmentalist nutjobs, thank you, R12 removal is one of the dumbass thing they do. And as for the last election thanx again, they are going to do things 1,000,000,000 times worse. So thanx for voting in the loony left! Morons!
Back to R134a. And R12. I was not going to to pay $40 a can for R12. R134a is doing a good job keeping my car cool. The a/c system pooped out at 200,000 miles. When it came time to put new parts in, R134a was the best choice. They car now has 350,000 miles. A/C works great.
btw,, those that claim they can get R12 cans in 12 oz can, here in California, and for less than $35.00 per can, please do, report back with where in California, and how much they cost..
Can someone please also report back an a/c service and repiar shop made you pay for R12, and how many oz you got for that price.
Thanx..
Last edited by retiredat44; 05-05-2009 at 04:51 PM.
retiredat44, R12 in 12 oz or 14 oz cans is always available in abundance on ebay for $15-20 a can in the winter and $25 a can in the summer. It ships ordinary first class mail or parcel post so the shipping is cheap too and you pay no sales tax if you buy from someone out of state.
Only Wisconsin prohibits buyers from importing it into that state.
retiredat44, R12 in 12 oz or 14 oz cans is always available in abundance on ebay for $15-20 a can in the winter and $25 a can in the summer. It ships ordinary first class mail or parcel post so the shipping is cheap too and you pay no sales tax if you buy from someone out of state.
Only Wisconsin prohibits buyers from importing it into that state.
a vague answer, and not in California,,
I did look on eBay, and it is like I said, even if you get a can for $25, you pay shipping, and it still ends up being about $40.00 per 12 oz. can for R12.
Period!
I bought a case of R134a @ 12 oz cans at Sams club for $36.00 ! The whole case is less than 1 12 oz can of R12 !
The R12 is cheap arguement (conversation) is not right ... and there are some people who will not let go of it... now imagine if you have small leak and you go through several cans of R12 at $40 a pop!
__________________
1989 Toyota Corolla SR5, Carb.
1993 Camry LE
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