First Post!! Help

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brcorp
Posts: 3
Joined: Fri May 22, 2020 2:03 pm

First Post!! Help

Postby brcorp » Fri May 22, 2020 2:36 pm

Hi! This my first post and I need help so Thanks in advance!!

I have a 2005 BMW X5 4.8iS. It has 95000 miles and is well maintained. The problem I'm having is my AC does not immediately cool after the car has sat overnight. I live in AZ so instantaneous AC is a must!!

In general what happens is the car is started cold the AC will not blow cold until the engine is to temp and has been revved to over 3500 rpms. Then the air blows great and will continue to blow great for the rest of the day even if its stopped, left to cool off and then restarted.

Here the typical scenario:

Outside temp 82 degF

Gauges hooked up Low 105 psi and High 105 psi

Start cold engine, let run/idle for a few seconds, flip on AC
Compressor is engaged
No change in pressures L 105 psi and High 105 psi
Interior fan running at 1/2 speed, vent temp 90degF
Electric radiator fan not running

Let car continue to run/idle, monitoring pressures, compressor engagement and radiator fan

Engine temp at 1/4 on the dash gauge
Compressor is engaged
No change in pressures
Interior fan running at 1/2 speed, vent temp 90degF
Electric radiator fan not running

Engine temp at 1/2 on the dash gauge (typical running temp)
Compressor is engaged
No change in pressures Low 105 psi and High 105 psi
Interior fan running at 1/2 speed, vent temp 90degF
Electric radiator not running

Quik rev engine to just over 3500 rpm then return to idle
Compressor is engaged
Pressures change Low 40 psi and High 250 psi
Interior fan running at 1/2 speed, vent temp 45degF
Electric radiator running

Engine idles for about 5 min and everything stays constant

Rev and hold engine to just over 2500 rpm
Compressor is engaged
Pressures change Low 30 psi and High 300 psi
Interior fan running at 1/2 speed, vent temp 40degF
Electric radiator running

Return engine to idles for about 5 min and everything stays constant
Compressor is engaged
Pressures change Low 40 psi and High 250 psi
Interior fan running at 1/2 speed, vent temp 45degF
Electric radiator running

If the quik rev to 3500rpms is done the engine temp is greater than 1/4 it typically wont have an effect. Engine temp needs to be at 1/2 position.

So once it kicks in it works great, it's the delay in startup that has me stumped!!

Any help would be greatly appreciated!!

Thanks,
Bill
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Cusser
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Joined: Sun Apr 24, 2016 6:29 am

Re: First Post!! Help

Postby Cusser » Fri May 22, 2020 2:50 pm

Bill - if your comfort is OK, then everything is OK.
Al9
Posts: 63
Joined: Tue Mar 10, 2020 3:26 am

Re: First Post!! Help

Postby Al9 » Fri May 22, 2020 3:19 pm

It's a Calsonic CSV717 variable compressor on your car. Sounds like your compressor bleeds pressure away from the crankcase (allowing the pistons to get into stroke and therefore start pumping refrigerant around; the compressor always starts operating with the swashplate in a near right angle relative to the shaft, and when the condenser fan is linked to a trinary switch or pressure transducer, the moment in which cooling begins and the condenser fan turns on is the very moment the swashplate suddenly tilts and the pistons get into full stroke in hot weather) only once it's heated up enough for some reason, and then it still needs some help to "unstick" something within and let the displacement control mechanism operate correctly. Could be a control valve (mechanical on your car) issue but not really sure about that. I have the early 2000s Delphi version of the smaller Calsonic CSV613 on my car and it does the opposite thing, i.e. for some reason it has a harder time bleeding pressure away from the crankcase when hot (though it's only a short term startup noise issue in my case and not a cooling one). Already changed the mechanical control valve on mine (for another reason though) and it's still doing the same thing so that's why i'm not sure it's just a control valve issue. These compressors are a real nightmare to diagnose. Also, they need the refrigerant charge to be as perfect as possible or they'll start acting weird.
brcorp
Posts: 3
Joined: Fri May 22, 2020 2:03 pm

Re: First Post!! Help

Postby brcorp » Fri May 22, 2020 5:02 pm

Cusser - I wish it was that simple but it's my wife's car so everything needs to work without issue.

Al9 - that is most info I've gotten after a year of digging!! Where did you find the displacement control mechanism??

Thanks for the replies!!
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JohnHere
Posts: 201
Joined: Sun May 13, 2018 10:20 am
Location: South Carolina Upstate - USA

Re: First Post!! Help

Postby JohnHere » Fri May 22, 2020 5:58 pm

Equal pressure on both the low and high sides also suggest to me that the compressor clutch might not be engaging and that you're seeing only static pressures. Are you sure the clutch is energizing, pulling in, and turning the compressor shaft when you turn on the system?
Al9
Posts: 63
Joined: Tue Mar 10, 2020 3:26 am

Re: First Post!! Help

Postby Al9 » Sat May 23, 2020 12:08 am

The displacement control mechanism is a complicated thing and can go wrong in different ways- it's actually the compressor's swashplate, the compressor's internal refrigerant passages, a small crankcase-suction bleed passage located on the reed valve plate, the control valve and the TXV.

Anything gets either somewhat "sticky" or clogged, compressor stays destroked and cooling gets poor or plain stops until it respectively "unsticks" or unclogs.

Examples of mechanical control valves stated as compatible with your compressor are Santech's MT2280 and UAC's EX 10349C. For some reason, mechanical control valves intended for Calsonic compressors don't seem to have different pressure ratings, unlike with Delphi/Harrison compressors.

I've used the blue rated UAC EX 10458C mechanical control valve (not compatible with neither CSV613 nor CSV717) to repair my compressor and though it's intended for Harrison V5/V7 compressors it's performing satisfactorily in my Delphi CVC-125 compressor.

If you're choosing to replace the mechanical control valve, keep in mind that any refrigerant left in the AC system must be recovered before attempting to pull out the old mechanical control valve from the compressor.

But, again, something could well be wrong with your compressor's internals rather than your mechanical control valve (or your TXV). Provided that the clutch is even engaging as JohnHere is saying, and provided that you have the correct refrigerant charge and no leaks at all.
Last edited by Al9 on Sat May 23, 2020 8:43 am, edited 1 time in total.
brcorp
Posts: 3
Joined: Fri May 22, 2020 2:03 pm

Re: First Post!! Help

Postby brcorp » Sat May 23, 2020 6:53 am

Yes, I've verified the clutch is engaged and the compressor is turning. I also verified when the AC is off the clutch is disengaged.

AI9 - you mentioned that this type of compressor is sensitive to pressure, do my pressures at idle and rpm look ok. I'm wondering if they're a bit high.
Outside temp ~85degF, engine at idle, Low 40 psi and High 250 psi, Interior fan running at 1/2 speed, vent temp 45degF

Engine at 2500 rpm, Low 30 psi and High 300 psi, Interior fan running at 1/2 speed, vent temp 40degF

Thanks!!
Al9
Posts: 63
Joined: Tue Mar 10, 2020 3:26 am

Re: First Post!! Help

Postby Al9 » Sat May 23, 2020 7:09 am

I'm afraid i'm not really expert about pressures so i'll leave them to other members.
User avatar
Cusser
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Joined: Sun Apr 24, 2016 6:29 am

Re: First Post!! Help

Postby Cusser » Sat May 23, 2020 4:11 pm

brcorp wrote:AI9 - you mentioned that this type of compressor is sensitive to pressure, do my pressures at idle and rpm look ok. I'm wondering if they're a bit high.
Outside temp ~85degF, engine at idle, Low 40 psi and High 250 psi, Interior fan running at 1/2 speed, vent temp 45degF

Engine at 2500 rpm, Low 30 psi and High 300 psi, Interior fan running at 1/2 speed, vent temp 40degF


Those pressures and vent temperatures sound pretty good to me. When your vehicles is moving through traffic you'll also get a ram effect of air through the condenser, and the high pressures will be lower than what you see with just the fan(s) moving the air.

I'm in Arizona too, and my '98 and 2005 Frontiers cool better and faster than my 2005 Yukon (all factory R134) which all do better than my 1988 Mazda truck (R-12). I like your vent temperatures. Next Thursday-Saturday will be 110F or over; but that's measured in the shade !
Al9
Posts: 63
Joined: Tue Mar 10, 2020 3:26 am

Re: First Post!! Help

Postby Al9 » Sun May 24, 2020 3:55 am

To me, vent temperatures look fairly ok for a Euro car intended for Euro weather. These are the same vent temperatures i'm getting from my AC system.
Might end up disappointing someone expecting vent temperatures always in the lower 30s though.

Fun fact is, with these compressors vent temperatures will get actually lower as high side pressure increases. The discharge pressure exerts a force that actually keeps the bellows from expanding (due to the decreasing suction pressure) and opening a passage which connects the crankcase with the discharge side. That is, as weather gets progressively hotter, the evaporator temperature at which the compressor will start destroking will progressively decrease.

With my system, which has a 42 psi suction pressure rated control valve, i noticed that vent temperatures got somewhat warmer once i got my 16 y old condenser replaced. Still comfortably cold, but no longer "hang meat" cold. AC engine load decreased accordingly. Similar behaviour has been noted in the past by other forum members running Harrison V5 compressors.

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