93 toyota pickup, low side good, high side climbing

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Djea3
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93 toyota pickup, low side good, high side climbing

Postby Djea3 » Wed Jul 25, 2018 10:02 am

Had a leak in my compressor. Replaced compressor, txv, dryer and condenser all new orings, flushed all lines, cleaned evaporator, oil charged etc.

After reassembly vacuumed and charged. Low pressure good, high pressure continually climbing. No issue with leaks.

Assessed blockage according to available information. Changed TXV, vacuumed and recharged. Now low side a little low, high side climbs to over 325 in a few minutes. No issue with leaks. Am at the end of available expenditures for this old beast and unemployed right now. Help me out a little?

Ambient at 80 to 85 degrees. I just checked the system and the (rental manifold) gages show 110 psi both sides (seems too high a pressure for temp). Can anyone help me with what is wrong here? I do have a manufacturing and some automotive background but this is my first ac system work.

I have a feeling that someone will know what this is.

Unfortunately my wife ac is going out now as well...damn....life sure throws curves.
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bohica2xo
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Re: 93 toyota pickup, low side good, high side climbing

Postby bohica2xo » Wed Jul 25, 2018 8:17 pm

The valves on the manifold need to be CLOSED to evaluate a system.

Run the system with the gauges attached, valves closed. Run it at idle, then at 2000 engine rpm. Record the pressures at both speeds, as well as the vent temperatures and ambient temperature. Post the results.
Djea3
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Re: 93 toyota pickup, low side good, high side climbing

Postby Djea3 » Thu Jul 26, 2018 7:04 am

Ambient 85
low pressure 40
high -starts at 225ish and climbs steadily> I shut down at 350ish
The vent temps are 50ish but.....this rise in pressure is so quick that I shut down.

Valves are closed when testing.

What is max pressure before I should shut down the system when testing? I do not want to harm the new components and system.

This morning I tried again. 80 degrees ambient, static pressures matched temp. It did the same thing. The climb in pressure on high side is steady, it starts a few seconds after stabilization at start and takes only a minute or two.
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bohica2xo
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Re: 93 toyota pickup, low side good, high side climbing

Postby bohica2xo » Thu Jul 26, 2018 7:54 am

The 110 psi static is probably just the refrigerant picking up engine bay heat.

You have a condensing problem. The OEM condenser is a Serpentine. A good design, but difficult to flush properly, and nearly impossible to tell is one or more channels are blocked.

Try using a garden hose on the condenser to see if you can control the high side pressure. Start with a light mist of water, and if that has no effect, soak it.

375 psi is not going to cause big problems instantly. I see those pressures here in Las Vegas on systems that are ok when the temp hits 115f like it will today. Anything over 400 psi I will shut down immediately.

1993 was a changeover year. Is this a 134a system, an R12 system - or a converted R12 system running 134a?
Djea3
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Re: 93 toyota pickup, low side good, high side climbing

Postby Djea3 » Thu Jul 26, 2018 12:03 pm

First this was a functioning system before the part replacement. The only issue was a VERY slow leak, as in a week or longer before any decrease in cooling.

Yes, when I cool with water on the condenser the high side pressure drops significantly. This is a new UAC condenser, should I consider it suspect?

OR....I have been thinking of alternative theories.....

1. too much oil (how much over spec is too much?) used supposedly 7 oz of pag 46 distributed through system per someone's online instructions. Compressor, dryer, evaporated and condenser. However, I was not able to get any oil to drain from the new compressor...so I am considering that there might have been some in there unaccounted for in the measure. Unfortunately in talking with UAC they have NO standard regarding the amount in a given compressor...and state that the amount should be on a tag...yeah..right.

2. air in system? (doubtful as this is the second time this has shown and I have been very careful in purging lines).
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bohica2xo
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Re: 93 toyota pickup, low side good, high side climbing

Postby bohica2xo » Thu Jul 26, 2018 1:18 pm

How significant was the drop with a wet condenser?

Generally this points to an airflow issue on the condenser.
Djea3
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Re: 93 toyota pickup, low side good, high side climbing

Postby Djea3 » Thu Jul 26, 2018 5:16 pm

it was significant, brought it down QUICKLY and with enough brought water splashed liberally and literally brought it to about spec. I used a laser across the condenser and down it. There were no obvious cold spots heat seemed to dissipate evenly top to bottom/ left to right etc

That is exactly what was wrong with wife's car. However this is an old truck and all was working perfectly before the change out of the condenser.....so....does this mean that the condenser is a problem in design and ability or that the fan clutch has a problem?

I did notice one thing in looking at the old condenser. It had foam gasket between it and the frame. The new one does not so there is a 1/2 inch gap around the sides so to speak. I am perplexed at this point. I sealed with 3/8 inch gasket material and it did not seem to help, but I did not seal it 100%.
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bohica2xo
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Re: 93 toyota pickup, low side good, high side climbing

Postby bohica2xo » Thu Jul 26, 2018 7:18 pm

Yes, a gap at the edge of the condenser can kill cooling. Get it sealed up completely.

Air bypassing the condenser and a weak fan clutch will do it every time. The water test says the condenser is ok, just needs OEM airflow.
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Tim
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Re: 93 toyota pickup, low side good, high side climbing

Postby Tim » Fri Jul 27, 2018 8:02 am

If you don't mind a little noise. You can lock up the fan clutch on the Toyota. Take the assembly off. remove the fan clutch from the blade. Take out the 4 screws holding the fan clutch assembly together. Open it up and drop 3 (triangle) 5/16 lock washers inside the clutch. Tighten it all down and the clutch assembly will be locked and more air flow.
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Djea3
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Re: 93 toyota pickup, low side good, high side climbing

Postby Djea3 » Fri Jul 27, 2018 10:43 am

Please remember that this was a functioning ac system except for a very slow compressor leak.
Ok, I checked the fan clutch, the fan will not spin more than 2 blades by hand cold or hot. There is no wobble in the clutch. The fan spins at about 640 at idle (laser tach) of 750 (laser tach with two reflectors reading 1500).

The idle up rpm seems to be correct and the engine runs nicely with ac on. The engine temp is in the low normal range as usual. As Stated I replaced with a full kit less evap, evap was cleaned and flushed. I can see light through both the radiator and the condenser so there does NOT seem to be any blockage there.

86 deg ambient temperature. engine warm. I blocked off all possible air bypasses except below the grille as that is design (allows air under the condenser to the radiator). I can feel airflow from in front of the condenser, but it does not seem to be very fast....just a fair flow. I checked with all areas of bypass closed off...2 rolls of paper towels on top between condenser and radiator (as if hood was closed).

Idle: low side 45-55 (varied a little) / high side rose to 360 +/- then slowly climbing to 390 before shut down. temp at top of condenser lasered at 180ish matching the expected temp for pressure. At idle the vent temp is 74 degrees.

1800 rpm 35/climbed to 400 before shut down. fan rpm 1050. vent temp is 72.

2000 RPM Starts at 50 ash/250ish....then changed....25/325 held then climbed slowly to 400. 74 deg vent

Notice that the vent temps may not be absolute lowest as shut down was only a moment or two. I was on full cold with car doors open to ambient.

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