Saab 9000 poor cooling

[cbraxton]

1996 Saab 9000 4-cylinder turbo, factory R134a system with Sanden SD7H15 compressor. This system uses a block-style expansion valve that does not have an external bulb. Several years ago the compressor, condenser, pusher fan, hoses, drier, pressure sensors, and expansion valve were replaced. It's an ACC setup with the heater core always in the loop, outlet temperature controlled by a mixer flap.

What's happening this summer is that cooling performance is poor, air is cool rather than cold under most conditions. On a hot sunny day at idle the outlet air will turn warm. Cooling is adequate only when outside temperature is below about 80 degrees and there is little or no sun. This is all with the compressor clutch engaged. Pressures at idle are about 30 psi low, 250 psi high at an ambient temperature of about 85 degrees. The condenser looks clean and the pusher fan and radiator fan work OK. Temperature mixing flap appears to be working.

Any suggestions of further diagnostics or the likely cause of the problem?

[cornbinder89]

Your high side pressure indicates a liquid line temp of between 145-150 deg F. That's too hot. You are not sheading heat at the condenser. Either air can't get though or the heat isn't being transferred to the fins.

[cbraxton]

Thanks, I'll examine the condenser more closely but it did look OK as far as being unobstructed and the fins being in decent shape. I'll also have to check temperature across it to see if it's partially clogged.

[cornbinder89]

You can spray water on the condenser and see what happens, if the high side pressure drops rapidly and the cooling increases, than you pretty much have nailed it down to the condenser.
The closer you can get the outlet of the condenser to ambient temp, the better it will cool.

[cbraxton]

Thanks for the tip! I should have time to try the water spray test later in the week, though I have no doubt you are correct given the symptoms.

I'm not looking forward to the prospect of replacing that condenser again, it's a bear to get to. The radiator, turbo intercooler, and oil cooler all have to come out and there is little clearance to work. If that's really what it needs I may not bother this summer since I have another car that has working AC for the hot weather.

[cornbinder89]

I know what you mean, I have a turbo 900 Saab. I am really impressed with these generic multi-path parallel flow condensers. I find I can fit a large capacity unit in the same space as the OEM and get very good results. I haven't done my 900 yet as I need to pull the engine/trans assemble for some other work, and that would be the time to replace/upgrade the condenser.
The down side to them is you need to make up new hoses, because nothing is in the exact same spot. Also, if a compressor goes bad, they will clog and you can't flush them. But with the price not to bad, you can look at them as saveing the downstream components.

[cbraxton]

The factory condenser on this car is parallel-flow since it came with R134a from the factory. The replacement I installed was a Nissens-branded unit that dropped right in and even had the built-in mount for the pusher fan. A larger condenser might be nice but really an OEM-style replacement should work OK on this car and I'd rather not get too involved in custom fabrication. (I've been in other Saab 9000s and their AC worked fine with factory parts.)

Since the compressor is working OK and not making any noises there shouldn't be any debris in the system unless maybe the desiccant bag in the drier broke open.

[cbraxton]

Just to follow up, I believe I've found the problem. Due to deterioration of the aftermarket condenser fan's electrical connector the fan was spinning way too slowly. It finally got to the point where it sometimes would not turn at all. I spliced in a direct connection and now the fan runs at full speed, which makes a noticeable difference in cooling. Just goes to show that you need to consider all possibilities when troubleshooting!

[Tom Greenleaf]

Good find, thanks for the follow- up.

Totally credible as lowering the amount of wire touching at least was the way to dim dash lighting and lower fan speeds.

A long term remedy for electrical connections and other things too that require lube and or totally water proof yet do not conduct electricity is Silicone grease also sold as "Dietetic" grease in a tube like tooth paste.

Sold more in brake specialty places than for automotive items/parts. It's totally rubber friendly.

The one nasty is if it's on something you plan to paint it's near impossible to remove it.

Again - thanks for the follow-up fix,

T

[cbraxton]

I figure someone else having similar symptoms can add this to their arsenal of trouble-shooting steps. When I first started looking into this problem I saw the fan was running so thought it was OK. It was not evident that it had been running too slow until it got worse. (That fan practically puts out a hurricane now compared to what it was doing before.)

Actually I was using dielectric grease, but that aftermarket connector basically disintegrated and the wiring was pulling out of it. With a solid, hardwired connection it shouldn't give any more trouble. It'll just be a little more work down the road if the fan needs to be replaced.

[Tom Greenleaf]

Again, glad you nailed it down without a total hunt.

While this and whole site is archived even if gone nice to follow up with what fixed what.

It makes sense anytime on plug connectors, light bulbs - assorted things to grease stuff that you may need to unplug later and it's still good for ages.

A warning on electric motors: Most are NOT meant for lowered power or voltage and would ruin the motors if that happened! Some are made like a starter motor for full power and short time of use and others continuous use - fans of any sort. Power locks, windows starter and the other motors however small are NOT meant for continuous use or burn right out.

This is why all starter motors I know of sense proper power or a solenoid chatters not turning the engine which actually saves the starter.

That grease (try this if you wish) is not water soluble even with salted road spray. Put a dab of that and regular grease in plain water. May take two weeks but regular greases usually turn whitish and more soap like and finally give out. They make everything for Marine use to be water proof as things are permanently under water so a place to find rust/corrosion tolerant items of many sorts for wiring as well.

One more: Stainless steel isn't always good! Check for quality if seeking stainless clamps or things with a magnet. Good stainless will lift stainless - cheap stuff won't. Try assorted silverware for a test just to see it if assorted types.

It all matters for the long run,

Tom

[cornbinder89]

Your high side pressure indicates a liquid line temp of between 145-150 deg F. That's too hot. You are not sheading heat at the condenser. Either air can't get though or the heat isn't being transferred to the fins.

When you see high liquid line temps, its time to look to why you are not sheading heat at the condenser, it doesn't always mean the condenser is at fault, it can be air flow, like in your case.