Check your radiator/condenser fan operation NOW

[DanG144]

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.

 

[LurkerMike]

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.

 

[LurkerMike]

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.

 

[ta79pr]

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

 

[DanG144]

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.

 

[ta79pr]

"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.).

 

[DanG144]

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

 

[hagar]

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.

 

[DanG144]

Is everything ok now?

 

[ta79pr]

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...

 

[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.

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

 

[BrianCT]

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.

 

[DanG144]

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

 

[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 ?

 

[DanG144]

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.

 

[cwarner]

the speed of the fans looks slow.. Oh and it's about 58 degree's outside. I don't know if that makes a difference.

If there is something wrong, where to I even start to trouble shoot ? I can here a solinoid /relay sound when they are starting/stopping. Could that be bad ? Both fans rotate easily by hand.

 

[DanG144]

I really did not figure that it was very warm in Michigan, yet.

Take a look at the AC clutch. What is it doing? See if it is engaging when the fans turn on, or when they turn off, or not at all. Look at the center of the AC compressor pulley, it is engaged when the center (and thus compressor) turns with the outside of the pulley. This may help us figure out what is going on.

I would start with the link in Post #1 that says
A4 fan troubleshooting

And depending upon what I find out go to this document,

Fan Repair

or whichever document below applies to your year car.


Sept 98 - May 99 Build date A4 Manual Air Conditioner Troubleshooting

May 99 - end of A4 Manual Air conditioner Troubleshooting

 

[cwarner]

I really did not figure that it was very warm in Michigan, yet.

Take a look at the AC clutch. What is it doing? See if it is engaging when the fans turn on, or when they turn off, or not at all. Look at the center of the AC compressor pulley, it is engaged when the center (and thus compressor) turns with the outside of the pulley. This may help us figure out what is going on.

I would start with the link in Post #1 that says
A4 fan troubleshooting

And depending upon what I find out go to this document,

Fan Repair

or whichever document below applies to your year car.


Sept 98 - May 99 Build date A4 Manual Air Conditioner Troubleshooting

May 99 - end of A4 Manual Air conditioner Troubleshooting

Cool,
Thanks for the links. Looks like I've got some work to do.

 

[DanG144]

I tried to upload a new rev of the AC troubleshooting PDF, and something is not working. It ruined the old document, and did not replace it.

I am not sure what is wrong. I have done this before, so I suspect I know how. The site just does not seem to be working. It is past my bedtime now, so I am signing off.

If anyone needs the May 99 and later A4 AC troubleshooting guide, send me a PM with an email address, and I will send you the document.

Dan

 

[DanG144]

Here is a new link to troubleshooting A4 air conditioners for cars built after May 99.

http://pics.tdiclub.com/data/517/A4_Air_Conditioning_Troubleshooting_Rev_41.pdf

 

[Jarmstrong]

Am i correct in understanding that these fans only run when the AC is on? so if i only have one working at idle, i can not use the AC until I find the time to fix it?

 

[DanG144]

The fans will run from radiator thermoswitch signals, from AC signals, and from ECU signals.

If only one fan is running from your AC signal, then it is likely only one fan will run from all of your slow speed signals. You may have two fast speed fans running, when you get a FAST speed requested, or you may not.

Your AC will work a bit harder, at higher temperatures and pressures with only one fan running. The AC compressor will age a little faster, but it will cause no short term problems.

 

[michTDI]

Dan-thanks for all the pdf's-and the fact that they contain pictures-they always help a LOT!!!

The AC on my A4 is working fine-at the moment-but the AC on BOTH of my B4's is not. One may just need a recharge-but the other one I have already tried that.

I realize the AC systems are probably different on the A4 versus B4-but I assume a lot of the troubleshooting/basic concepts would be similar-correct???

In my experience there are a quite a few people that know quite a lot about TDI's........but even a lot of the "TDI gurus" often know very little about the AC........and usually if you take a non-working AC to a local AC place or a dealer for that matter the bill will be HUGE........and I'd suspect that often that is because they "replace parts"-instead of just getting it to work/really troubleshooting the problem.........

So this is especially needed-and yeah this should definitely be a "sticky" or put in the "how-to" area permanently-thanks again!!!

 

[Jarmstrong]

any idea what the resitance should be on the plug for the driver side fan?

how about for the wires on either side of the resistor inside the fan motor.

thanks

 

[DanG144]

Look at the photos and captions near the end of the fan troubleshooting guide in post #1 of this thread. It covers the fan resistances.

Here is a copy of a photo caption:
"This is a shot of the drivers side fan connector. Note the spade connections. In this shot pin 1 is bottom, pin 2 middle, pin 3 top. These are 1/4" spades. The resistance on my good fan was 1-3 0.6 ohms, 1-2 0.8 ohms, 2-3 1.2 ohms."

You will have to be more specific on what you are asking for about the resistances on the internals. (And I would have to go and measure one.) The important internal resistances should be the same as those measured from the plug. You are essentially measuring:
pins 1-2 across the resistor.
pins 1-3 across the fan winding.
pins 2-3 across both the fan winding and resistor in series. (I know they do not quite add up, but that is life; not perfect but good enough.)


The resistances across the brushes should be on the order of 0.1 or 0.2 ohms.

Does that help?

 

[Jarmstrong]

thank you. my resistances read alot more than that but it works so i'll call it good. and i couldn't even get a good reading from one end of the resistor to the other.

thanks

 

[dmorrell]

I am having an issue with my A/C were it works first thing in the morning, but when the car has been sitting outside all day in the sun (I live in Florida, so the outside temp is between 88F to 100F deg) the A/C will not come on for about 10 minutes or so. I did some investigating. Both fans come on just as described in the above posting. I noticed that the compressor was not running. After about 10 minutes sure enough the compressor started and the A/C was working. I went out and bought a Freon re-charge kit to see if the Freon was low. It was not the case. The pressure measured around 48 PSI on the low side. According to the directions on the side of the Freon can the PSI should be between 45 and 55 PSI when the ambient temperature is around 95F.
I am not sure why the compressor is not turning on right away and waiting 10 minutes before turning on. It only seems to happen when the car has been sitting out in the sun for long periods of time. Any help would be greatly appreciated.

Thanks,
Daryl

_________________________
2005.5 Jetta TDI

 

[DanG144]

Freon?

Our air conditioners should not be using Freon, but R134A, and I am pretty sure the pressure should be about 110 psi for 95F. This is in equilibrium, if it is 95 out, but the refrigerant is boiling out of your can, then the pressure would drop, and the can cool off.

some people have published that some pressure gauge fittings will not open the schrader valve on the A4 VW - that they can be problematic.

The low pressure cutout should actuate at about 14.5 psig, and reset about 70 psig (as sensed on the high pressure side of our systems). So even with 45 psig you would be above the low pressure cut off.

All that being said, it sounds as if the most likely problem is a faulty ambient temperature sensor. This is located in the plenum under the windshield for most A4 cars with manual AC, on the left side. I do not have a tech manual, or any experience with the A5 cars, or for climatronic AC.

Do you have climatronic AC?

The only way to tell for sure what is going on is to do some troubleshooting. The A4 troubleshooting would probably work fairly well if you have manual AC, but not if you have climatronic.

Let me know what type of AC you have. I may be able to look into it.

 

[dmorrell]

Thanks for the correction, It would be R134A and not Freon. I assumed that R134A was just another form of Freon.

I do have the climatronic AC.

The system was reading about 100PSI (that was about as high as the gauge would go) with the compressor off and 48 PSI with the compressor on.

 

[DanG144]

Thanks for the update. That all sounds normal.

If you can get someone with a CAN bus VCDS, the diagnostics and trouble codes for a Climatronic read pretty good. (I have never done it, just read about it.) So a VCDS inspection may show what is holding out your clutch.

Dan