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chamilka

Solved !!A/C issue: works when ignition is On but not when running

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Car 2003 996 C4S.

Problem:

Today, during a short drive my A/C stopped working.  When the engine is running there is no air coming through as if the fans are not working. However, when the ignition is turned on without starting the cars then cold air comes through.

What could be the problem?

 

Edited by chamilka

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A/C fuse or relay could be the problem.

Do the radiator fans come on?  Should be always on if A/C is operating.

Doesn't sound like an A/C dash control issue, but I wonder about that too.

Good luck.

 

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Thanks

Both left and right radiator fans do not come on when the engine is running while the A/C is on (full). 

I checked the two fuses C8 & C10 and they both are good.

the relays typical don't go bad right?

I can try to jump relays an see if that do anything but I tend to think the cooling fans are shot?

 

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Update:

1. Fuse - OK

2. Jumped all four Relays - Left & Right cooling Fans came up for both stage 1 and 2 - This confirms that the Fans (motors) themselves are good right?

So I assume either relays or the Resistors bad? 

Is there a way to test the resistor? or does my step #2 confirms the resistors are the problem?

Thanks

 

 

 

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5 hours ago, Loren said:

If you can get both stage 1 and stage 2 fans speeds then the resistors are likely okay.

 

so you think the Relays are bad, I wonder why all four went bad?

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Hi Chamilka! Do you have a Durametric? Would be a lot easier to diagnose if you have one.

Your problem sounds very strange. when you said no air coming through, did you really mean the a/c blower under the dash is not running?

With engine ON, can you turn on the a/c blower fan with the a/c OFF? Do you have air coming through that way?

 

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I was able to activate both fans to run in stage 1 and 2 using both durametric and by jumping the relays. this confirms the fans are working.

I also bough new et of relays and swap them but no results, which confirms the relays not the issues.

The problem is that the two Radiator Cooling fans do not come on, these fans supposed to come on when either A/C is on (full) or when the temp is high. When I start the engine and turn the A/C to max none of the fans start.

In addition to that the A/C also does not blow air, I confirmed that that the  A/C Blower motor (under the dash) is not the issue. While ignition is on without turning the engine A/C bower motors comes on  blows air.

Edited by chamilka

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perhaps something in defective in the dash heater-a/c control, or something is shorting out or overloading when engine is started.

I think the a/c head is a drop in unit.  probably fairly expensive.

Never heard of this issue happening before.  continued good luck hunting for an answer.

Edited by judgejon

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I also posted another thread regarding  Series resistor clarification, it looks different form what I expected to see.

 

Edited by chamilka

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15 minutes ago, chamilka said:

 

I was able to activate both fans to run in stage 1 and 2 using both durametric and by jumping the relays. this confirms the fans are working.

I also bough new et of relays and swap them but no results, which confirms the relays not the issues.

The problem is that the two Radiator Cooling fans do not come on, these fans supposed to come on when either A/C is on (full) or when the temp is high. When I start the engine and turn the A/C to max none of the fans start.

In addition to that the A/C also does not blow air, I confirmed that that the  A/C Blower motor (under the dash) is not the issue. While ignition is on without turning the engine A/C bower motors comes on  blows air.

 

Indeed very weird. Did you scan the climate control module using Durametric? Any error codes?

Can you also check if the compressor engages at all?

 

I think Judgejon maybe onto something with the control unit being faulty. I wonder if it's as simple as a sensor issue e.g., a faulty sensor things the temp is way low so that prevents the a/c from operation all together.

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BTW, I agree the problem is not in the cooling fans, resistors, and relays because of the Durametric test results.

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1 hour ago, Ahsai said:

BTW, I agree the problem is not in the cooling fans, resistors, and relays because of the Durametric test results.

crap!!

I will have to return the Resistors then, in wane I removed the fan!! that was a pain. let me run some more diagnostics and post results.

 

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So I ran the diagnostic against the A/C unit.

only error I got was 38: PCM CAN timeout fault which I had for a long time. this is due to installing after market head unit.

 

 

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Just to be clear, I get cold air when the ignition is turned on, why would it get cut when the engine is running :)???  

Edited by chamilka

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With key ON engine off, use Duratmetric Activation under a/c or dme (I forgot) to activate the compressor clutch, air blower fan, and servo motors on the air blower box.

 

With key OFF, remove both fuses E5 and A7 and leave them uninstalled. Check them and then reinstall them. See if that makes a difference.

Edited by Ahsai

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Under A/C Activation, there are six options and two of which include:

  • A/C request signal and

  • Fresh air Fan

When activating A/C request signal the Snow flake symbol appears on the climate control display.

Activating Fresh Air fan will blow air, since the A/C was on air was cold.

Capture.GIF

Edited by chamilka

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you might check out the cost of a new control panel unit.  

I know from numerous forum topics that the each dash unit can be taken out and dash positions rearranged.

So maybe there is a way to test your control, and if faulty maybe swap it out for a replacement.

Or, if everything else fails, change it just to see if a new one might solve the problem.

good luck with all this...  the answer will be no doubt be interesting.

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$850 for the remanufactured unit at Suncost . :) 

thats bunch of cash !! 

Do these units tend to fail - not sending signal to blower and compressor? 

If the freon is low could that shut the Ac compressor from coming on? 

By the way the radiator fans came on after a long drive so at least that's good news :) 

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9 minutes ago, chamilka said:

$850 for the remanufactured unit at Suncost . :) 

thats bunch of cash !! 

Do these units tend to fail - not sending signal to blower and compressor? 

If the freon is low could that shut the Ac compressor from coming on? 

By the way the radiator fans came on after a long drive so at least that's good news :) 

Hence my comment on modulemaster.com but you need to make sure that's your problem first.

If the refrigerant is low, the a/c compressor will NOT come on. There's a pressure switch to detect that. You can hook up an a/c pressure gauge on the low pressure side to check for pressure.

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On ‎9‎/‎12‎/‎2017 at 12:19 PM, Ahsai said:

Hence my comment on modulemaster.com but you need to make sure that's your problem first.

If the refrigerant is low, the a/c compressor will NOT come on. There's a pressure switch to detect that. You can hook up an a/c pressure gauge on the low pressure side to check for pressure.

Thanks man, I plan to check the low pressure side today. I have a question: I have heard that the A/C has to be running full blast in order to check the pressure, would I get an accurate reading without the compressor running? Supposed I have low refrigerant, would I be able to fill it while the compressor is off. I have filled refrigerant in the past for other Porsches while the compressor had to be running hence the question.

 

Edited by chamilka

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John  is right. However, you can still check the static pressure when the engine is off. It should be ~70-80PSIG on either low/high side (temperature dependent).  If you have some very low numbers, your pressure switch will prevent the compressor from being activated.

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