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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old April 12th, 2009, 11:48   #31
DanG144
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Quote:
Originally Posted by ta79pr
are the low and high wires two sets of brushes within the fan? NEVERMIND, i see the internal pics now - I guess it is just a resistor(s). I have high speed operation but no low speed. is there a common reason the low doesnt work, wiring\module, etc.?
When do they come on in high speed? Look for a PM and call me, if you wish.

What kind of test were you doing to see high speed operation? Or was it just during normal operation?

The UK forum said they see a lot of failed resistor connections. I have only seen bad brushes and holders.

I did have one fan that would run in fast but not slow, and it was the brushes not the resistor. Apparently it was only making partial contact, and the lower voltage in slow was not providing enough torque to get it to move, but fast speed full voltage was. At least that was my conjecture, because the only problem was with the brushes.

Last edited by DanG144; April 12th, 2009 at 11:55.
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Old April 12th, 2009, 23:02   #32
LurkerMike
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Originally Posted by DanG144
I think you should have used 800 grit emory cloth instead of sandpaper, otherwise a good job.
I could have used 80 grit and it would have made it smoother than it was... I wasn't able to sand all of deep scored rings and grooves out, mainly I was just trying to polish the burnt carbon off of the copper.

I also sanded the ends of the brushes to remove most of the ridges there too so they could get a fresh start at reseating.

I must not have done the low speed test correctly the first time when I thought both fans had failed.

I hooked my gauges to the lines and found about 30psi static... All I had was one small can of R134 on hand so I shot it to it... it is still low on the pressure as the coldest point reads around 36* F and I like to charge them to around 40*... but the compressor clutch appears to be cycling now as evidenced by cold air from the vents now.

I usually convert all my cars to R416A no matter what they came with. R416A is an R134 blend that is a drop-in replacement for R12... it makes a lower head pressure than R12 and is like 98% as efficient in an R12 system. I like it because if the ceramic compressor seal is seeping, like all will do someday, the lower head pressure reduces the rate of loss.

And in theory, because R416A runs at a lower head pressure, less parasitic loss of horsepower is consumed to make the cold air... and idiots like me that crank out high rpms with the A/C on, are not damaging the compressor as badly... I am a believer that the higher the rpms an A/C compressor is forced to turn, the shorter its life.
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Old April 12th, 2009, 23:03   #33
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Quote:
Originally Posted by DanG144
I think you should have used 800 grit emory cloth instead of sandpaper, otherwise a good job.
I could have used 80 grit and it would have made it smoother than it was... I wasn't able to sand all of deep scored rings and grooves out, mainly I was just trying to polish the burnt carbon off of the copper.

I also sanded the ends of the brushes to remove most of the ridges there too so they could get a fresh start at reseating.

I must not have done the low speed test correctly the first time when I thought both fans had failed.

I hooked my gauges to the lines and found about 30psi static... All I had was one small can of R134 on hand so I shot it to it... it is still low on the pressure as the coldest point reads around 36* F and I like to charge them to around 40*... but the compressor clutch appears to be cycling now as evidenced by cold air from the vents now.

I usually convert all my cars to R416A no matter what they came with. R416A is an R134 blend that is a drop-in replacement for R12... it makes a lower head pressure than R12 and is like 98% as efficient in an R12 system. I like it because if the ceramic compressor seal is seeping, like all will do someday, the lower head pressure reduces the rate of loss. As you probably know, R134A runs at head pressures much higher than R12.

And in theory, because R416A runs at a lower head pressure, less parasitic loss of horsepower is consumed to make the cold air... and idiots like me that crank out high rpms with the A/C on, are not damaging the compressor as badly... I am a believer that the higher the rpms an A/C compressor is forced to turn, the shorter its life.

Last edited by LurkerMike; April 12th, 2009 at 23:06.
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Old April 15th, 2009, 21:55   #34
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I read the thread this weekend, realized the mk4 jetta was dead on low speed. I did all the tests and finally confirmed it was the fan(s) by direct wiring them to the battery. They both worked great in high, but neither worked in low.
Finally took the driver side (larger) one out tonight. I hacked it open, the brushes were in great shape and moved freely. However there was a broken wire to the big resistor. I resoldered it the best i could and slapped it all back together.
Here is the strange part. Now both fans work in low. I am positive that I checked both and even direct wired both. I am thinking they are in series when in low. But the schematic may prove me wrong...
Anyway, great thread, thanks Dan!
I didnt take any pics of the resistor repair because the ones in the euro forum are well taken and it is easier to just link.

pics 11-17 here at the euro forum (except ours only have two brushes as Dan's pics show).
http://uk-mkivs.net/forums/p/2088/17772.aspx#17772
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Old April 16th, 2009, 03:23   #35
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The fans are not in series in low speed; they are in parallel.

It is good to know about the resistor.

Keep an eye on the fan that mysteriously started working. I have seen that happen several times. I would still suspect that it has a problem with the brushes or resistor, and is working only intermittently.

Which is why I check mine about once per month, usually when refueling, since I am under the hood checking the oil anyway.
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Old April 16th, 2009, 05:40   #36
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"The fans are not in series in low speed; they are in parallel."

yeah, that is what i thought when I read the schematic. I am going to buy a soldering gun (my little iron took too long) and just address the smaller fan now for piece of mind. These cars are plagued with bad solder joints (relay 109, door switch circuit board, antenna, etc.).
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Old April 16th, 2009, 09:53   #37
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Would you be willing to come by and do it at my place this weekend?

I would like to meet you. Would you want a VCDS checklist done on your car? The cost is right - free.

Dan
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Old April 16th, 2009, 11:12   #38
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I had a fan that had an intermittant short, sometimes it would run and sometimes not. When I finally realized it was bad, I replaced it right away, but guess what? Three months later my aircon conked out, and another 3 months after that, my alternator went. I'm pretty sure it was all related.
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Old April 16th, 2009, 12:53   #39
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Is everything ok now?
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Old April 16th, 2009, 14:31   #40
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i cracked the ceramic case around the resistor, i figured no problem, add some epoxy putty to the ceramic holder and all would be well.
however, the wife complains that the car smells like, well - burning epoxy. so i guess the epoxy putty cant handle that kind of current/heat.

i will have to get a hold of the guts of a dead fan for the resistor, or buy a replacement. I think it is just a heavy duty 1 ohm.

I noticed the 3 of us chiming in, us Columbia area folks should get together at some point when the schedules permit. Besides I still have a transmission control module Hagar might want...
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Old April 16th, 2009, 14:54   #41
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Someone is working on a TDI at my place at least two weekends a month. You are both welcome, almost any weekend. Just PM me first.

I have a fan that (I am pretty sure) has a good resistor. The Fan holder is ruined on it. We should be able to get one of them running, don't you think?

I also have one repaired fan, just sitting around for a spare. I will have to go see which side it fits, if you want?

I am off now, so you could try to fix it this evening or tomorrow (off again), this weekend, or some other time.

Dan
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Old April 16th, 2009, 16:27   #42
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Quote:
Originally Posted by DanG144
Someone is working on a TDI at my place at least two weekends a month. You are both welcome, almost any weekend. Just PM me first.
Dan
Dan,

You're like a gift that keeps on giving.

I'm certain you've woke up a huge population of the MKIV board to check their aux fans. I, for one did, and I thank you for it. What drew you to researching this issue so thoroughly?

Again, thank you for this thread.
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Old April 16th, 2009, 16:57   #43
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A young lady came to my first GTG, just 4 or 5 months after I bought the car. She was married to a serviceman, and needed some help on her car. We were able to help a good bit, but she was having AC and fan issues, and no one there could help. A quick search on the forum provided little help.

So learning about AC and fans seemed a worthwhile service to the TDI community...something to pay back all the other folks who helped me and taught me a lot about these cars.

Dan
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Old April 19th, 2009, 11:44   #44
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Just checked mine.. both fans work. They do cycle though, they will run for several seconds then stop then run etc.
Is this the normal ?
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Old April 19th, 2009, 12:37   #45
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Quote:
Originally Posted by cwarner
Just checked mine.. both fans work. They do cycle though, they will run for several seconds then stop then run etc.
Is this the normal ?
No, this is not normal.

When the AC is on they should immediately start in slow, and run continuosly in slow. If it is too hot outside, then they will periodically shift to fast, with period of slow in between.

It sounds as if your fans are not running in slow speed, just fast speed. They do this when the compressor discharge pressure gets too high.

This type of cycing operation overheats the circuitry for your fans. Usually the 30 amp fuse above the battery, but sometimes another electrical junction, or even the contacts in your fan control module.

I would troubleshoot further as soon as time allowed.
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