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mday
Nürburgring


Joined: 20 Mar 2008
Posts: 433
Location: Deepest Darkest West Sussex

1996 Porsche 993 Carrera 4S

PostPosted: Thu Apr 29, 2010 4:17 pm    Post subject: Reply with quote

Yes: I ran both fans on slow speed for about 5 minutes; the resistor bodies get quite hot to touch but the heat sinks were doing a good job & I could touch the sinks easily after this time. I got the impression that they wouldn't get any hotter; in any case the thermal cut-out would switch the current off at 70 deg C if it did.

Now the difficult one: I assume because there is a big vent hole just above the resistors, & there is a nice channel in the front part of the wheel arch liner, that there is an air flow over the resistor once the car is on the move: the question is of course where does this airflow go to/come from?
 
  
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samba-lee
Suzuka


Joined: 19 Aug 2008
Posts: 1050
Location: Manchester

1974 Lamborghini urraco

PostPosted: Wed Jul 07, 2010 8:44 pm    Post subject: Reply with quote

Hi all,

I spent most of last night going through the details of the resistor replacement mainly to understand how all the fans should operate. So this afternoon I decided to test them and to my disappointment Smile they both worked at slow speed. I was quite surprised as I though they would be toast by now - maybe they are nearly toast so I'll need to do them at some point, or maybe they have been done. Disappointment as I was fired up to fix something on the car Smile

I've only heard the oil cooler fan come on once, on high speed and my temp rarely gets beyond the first significant mark on the guage. It came on with the temperature at about 9 o'clock - is this normal ? and when should the slow speed cut in ?

I assume that the A/C fan simply won't work until I get my A/C working, but that's a different story.

Lee
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Drew
Nürburgring


Joined: 28 May 2004
Posts: 433



PostPosted: Thu Jul 08, 2010 7:08 am    Post subject: Reply with quote

samba-lee wrote:
Hi all,

....and to my disappointment Smile they both worked at slow speed.


Floor very good
 
  
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johndonne
Newbie


Joined: 24 Jan 2009
Posts: 14



PostPosted: Thu Jul 08, 2010 8:02 am    Post subject: Reply with quote

My A/C has been blowing warm recently so I jumped the A/C fan and oil cooler fan resistors, and found that the A/C fan resistor needs replacing - it only runs on high speed. I checked the fuses and switched the R04 and R14 relays. Over the weekend I tried running it for ~20mins at high speed whilst on the motorway, but the A/C still isn't cold. Should that happen, or does that mean there's another problem too? The compressor seems to engage OK, and it's been two years since the system was re-gassed. Last summer the A/C was really cold, just perfect. The oil temperature has been quite high too, but I assume that's because of the heatwave here.

I've just received the replacement resistors and will fit them this week, and will clean in front of the condenser whilst I'm at it...

I've spent a lot of time researching this topic in the forum archive, but would appreciate if you have any ideas.

Thanks.
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samba-lee
Suzuka


Joined: 19 Aug 2008
Posts: 1050
Location: Manchester

1974 Lamborghini urraco

PostPosted: Thu Jul 08, 2010 9:25 am    Post subject: Reply with quote

johndonne wrote:
My A/C has been blowing warm recently so I jumped the A/C fan and oil cooler fan resistors, and found that the A/C fan resistor needs replacing - it only runs on high speed. I checked the fuses and switched the R04 and R14 relays. Over the weekend I tried running it for ~20mins at high speed whilst on the motorway, but the A/C still isn't cold. Should that happen, or does that mean there's another problem too? The compressor seems to engage OK, and it's been two years since the system was re-gassed. Last summer the A/C was really cold, just perfect. The oil temperature has been quite high too, but I assume that's because of the heatwave here.

I've just received the replacement resistors and will fit them this week, and will clean in front of the condenser whilst I'm at it...

I've spent a lot of time researching this topic in the forum archive, but would appreciate if you have any ideas.

Thanks.


There's talk of the A/C fan contributing to the overall cold air output, but I guess if you've run it on the motorway then that doesn't matter. Of the compressor engages then you must still have some gas - maybe you've not got enough and it needs topping up - Kwikfit would be your friend here. If it's low then the gas has obviously escaped and I think you know what that means.

Lee
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Zingari
Brands Hatch
Brands Hatch


Joined: 25 Oct 2009
Posts: 13154
Location: Cheshire

1993 Porsche 964 Anniversary

PostPosted: Thu Jul 08, 2010 9:31 am    Post subject: Reply with quote

John

I doubt replacing the AC ballast resistor will assist with chilling the air. It sounds to me that if you are not getting chilled air you have a problem with your AC - condensor, evaporator or expansion valve (sits above the evaporator). The first is easy to fix, the second a nightmare and the third is easy.

If your compressor clutch is kicking in and out then it might be that your gas is low from a slow leak.

I would take it to Kwik-Fit for a £49 regas. If they diagnose a leak or cant get the air chilled then you dont pay Thumb Once this is done work from there.

Lee - I seem to recall that my AC condensor fan would still kick in and out when I pressed the snowflake on the HVAC even thouth the compressor was not not cycling. Doing the test by shorting across the relay pins will confirm if the fan works at both speeds.
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samba-lee
Suzuka


Joined: 19 Aug 2008
Posts: 1050
Location: Manchester

1974 Lamborghini urraco

PostPosted: Thu Jul 08, 2010 9:39 am    Post subject: Reply with quote

"The first is easy to fix, the second a nightmare and the third is easy. "

I thought the expansion valve was as difficult to get to as the evaporator - how do you change it then ?

Right off to see if my A/C fan comes in with the big snow flake... (even though I know the compressor doesn't and I have no gas)

Lee
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Jack Frost
Hockenheim


Joined: 28 Jul 2009
Posts: 628
Location: Hampshire


PostPosted: Thu Jul 08, 2010 9:41 am    Post subject: Reply with quote

My fresh air flap was why I was getting cool air and not cold air through.
When you press the recirc button you should be able to see that the arm has moved on the fresh air flap (in the middle under the cover under the bonnet - it's a white arm connected to a metal rod). Check this with the ignition on obviously.

If this is not working then you are dragging warm air from inside the car through the air con.

At the end of the day it's a quick check that won't cost anything.
 
  
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samba-lee
Suzuka


Joined: 19 Aug 2008
Posts: 1050
Location: Manchester

1974 Lamborghini urraco

PostPosted: Thu Jul 08, 2010 9:57 am    Post subject: Reply with quote

Jack Frost wrote:


If this is not working then you are dragging warm air from inside the car through the air con.

At the end of the day it's a quick check that won't cost anything.


Good point but don't you mean dragging warm air from outside the car through the aircon... ? it's supposed to recirculate to get colder.

My fresh air flap servo was bust, but I only knew because it showed up on the OBD (Durametric) diagnostic. It's a poor design is some ways as it's always moving - it adjusts itself with road speed apparently so bound to have a limited life as compared to the other servos in the system.


Lee
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samba-lee
Suzuka


Joined: 19 Aug 2008
Posts: 1050
Location: Manchester

1974 Lamborghini urraco

PostPosted: Thu Jul 08, 2010 10:14 am    Post subject: Reply with quote

Yeah A/C fan comes on slow speed when the blower is turned on and the small snowflake button pressed (and obviously when the big snow flake button is pressed as well)

Lee
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Zingari
Brands Hatch
Brands Hatch


Joined: 25 Oct 2009
Posts: 13154
Location: Cheshire

1993 Porsche 964 Anniversary

PostPosted: Fri Jul 09, 2010 3:52 pm    Post subject: Reply with quote

Expansion valve sits on top of the evaporator and under the flap servos. Led to believe that it is popssible to remove without too much difficulty - but obviously a few bits have to come off to get to it.

From reading the US Forums it is likely that UK owners will have other issues as the expansion fault is when it ices up the evaporator (over chilling) in hot climates and thsi decreases cooling after it has been on for some time.

Lee - That place in Salford can inspect for leaks but suggest if you take it there you take out the inner wheel liner etc beforehand as they will not be familiar with our cars.
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johndonne
Newbie


Joined: 24 Jan 2009
Posts: 14



PostPosted: Sat Jul 10, 2010 7:05 pm    Post subject: Reply with quote

Thanks for your input. I'll check next week for other issues, including regassing, and let you know what happens.

~JD
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johndonne
Newbie


Joined: 24 Jan 2009
Posts: 14



PostPosted: Thu Jul 15, 2010 9:01 pm    Post subject: Reply with quote

Quick update: I haven't got around to replacing the dead A/C resistor yet, but based on the advice received here I went ahead and got the A/C system re-gassed by a specialist recommended by my indie, who confirmed right away that this was the main issue. Per my earlier post, the A/C condensor will only work on high speed right now, but it's blowing nice and cold again Smile

Thanks again for the input, and I hope this feedback also helps someone here.

Btw, they reminded me that it's best to run the A/C occasionally during the winter months, even just for a few minutes every few weeks.

Having now received the replacement parts (identical part numbers), I will replace both the A/C and oil cooler resistors ASAP.

~JD
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samba-lee
Suzuka


Joined: 19 Aug 2008
Posts: 1050
Location: Manchester

1974 Lamborghini urraco

PostPosted: Mon Jul 19, 2010 9:20 pm    Post subject: Reply with quote

Had some time this afternoon so called into Kwikfit on the way home for a "free" re-gas. I've never seen my A/C work and I know there was no gas in it - thus it was a bit of an experiment.

Interesting to watch the process with their automated machine. First vacs the system out, does a leak test and if it passes it re-gasses the system. I was suprised to see mine actually pass the leak test and so it was a pleasant suprise to finally see the A/C compressor work for the first time since I bought it. Still working 7 hours later Smile lets see how it goes over the next few days, I don't expect it to last - either way I'm chuffed to get this far and Kwikfit were very informative with their process.

Earlier on in the year I replaced a very rusty filling valve so I'm hoping that the leak was because of that...

Lee
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Zingari
Brands Hatch
Brands Hatch


Joined: 25 Oct 2009
Posts: 13154
Location: Cheshire

1993 Porsche 964 Anniversary

PostPosted: Tue Jul 20, 2010 12:33 pm    Post subject: Reply with quote

Lee - if the gas drops out over the next few days take it back (not the gas) you should get a refund from Kwik-Fit as they should have found the leak but sometimes they dont show up.

I'd also give it a good long run on high AC to get the oil circulating in the pipes
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samba-lee
Suzuka


Joined: 19 Aug 2008
Posts: 1050
Location: Manchester

1974 Lamborghini urraco

PostPosted: Tue Jul 20, 2010 6:51 pm    Post subject: Reply with quote

Zingari wrote:
Lee - if the gas drops out over the next few days take it back (not the gas) you should get a refund from Kwik-Fit as they should have found the leak but sometimes they dont show up.

I'd also give it a good long run on high AC to get the oil circulating in the pipes


Sure, I do expect it to drop but I'm still happy that it all seems to work at least (or did, not tried it today yet). Thus if there are leaks then they are worth investigating now as there should be a positive outcome - just fingers crossed.

Incidentally, I noticed that the fresh air flap had stopped working (again). Replaced the servo last year with a used one (£5) - you can hear it just after you turn the ignition off as it opens/closes for a few seconds - a little whirring noise. Also it came up on the OBD software.

Servo feedback contact surface on the circuit board inside was toast, but I still had the old servo where the motor had blown but the circuit board was good, so I swapped them over and it was all good. There are expensive little suckers too (~£140) so better to fix.

oh yeah, I knew there was a point Smile the expansion valve is right below the fresh air servo. This and one of the other servos take about 5 minutes to get out and that's about as much access as you will get, but I guess that must be enough to get to the expansion valve.

I wonder why the evaporators actually get to leak ...? I mean you can understand it with the condenser rad given its position.

Lee
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ToreB
Approved Trader


Joined: 13 May 2010
Posts: 617
Location: Oslo, Norway


PostPosted: Sun Jun 12, 2011 2:57 pm    Post subject: Reply with quote

I've heard that the Porsche evaporators are not good enough and does not stand up to the corrosion possibilities due to the condensed water and dirt around the pipe joints.

Cheers,
Tore
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