Rear air in Suburban not cold

[drewkeen]

The rear air in my Suburban is not blowing cold at all. The air comes out like it should but feels the same as ambient air. The front air blows cold when I am moving but when I sit still for more than one or two minutes it slowly starts to get warmer and approach ambient. Where should I look first?

Thanks!

[sidehackbob]

Front and rear air are really just 2 ends of one hose, so to speak.

your marginal performance up front will magnify losses to the rear. R134 systems really have to be "up" to work well. R12 could tranfer heat faster so a marginal charge would still cool. It is also possible for a R134 system to be ok and not work in the driveway, you need air moving over the condenser out front to get the thermodynamic cycle working. Check the condenser for any folding of fins and make sure the space between the radiator and condenser is clean.

[Robyn]

You really need to stick a set of gauges on the system and see what the pressures are.

High side needs to be up about 175 or so and the low side should be down in the mid 30's when the system is running.

The high side will run higher when the weather is warm too.

when the system is working right it should cycle the clutch every so often as the system draws down into very low pressure.

The front is an orifice tube and the rear is controlled by an expansion valve.

Try using some 134 cans and add some refrigerant with the system running. (Add to the low side fitting)
Once you get good cold air you are probably close enough.

Look the system over and see if there are any visible oil stains on the fittings indicating a leak.

If you find a leaky area fix the leak then recharge the system.

[drewkeen]

I'll go put some gauges on it tomorrow. Do I need to let it run for a few minutes before checking the pressures?

My suburban is a 1995, is it r134? I think I saw a sticker under the hood that said it was but I am not positive.

[Robyn]

Yes R134A

Let it run for a couple minutes to get the pressures stable.

[cshade]

odd factoid: my rear ac blew ultra cold and my front ac was just above ambient. Added some 134 and it improved the front quite a bit, but rear is still ten degrees colder

[cshade]

the above problem was due to a weak compressor. Problem solved, I'm hanging meat right now.