radiator/ac fan wiring question

i cant get ahead this week. pulled wifes car around to check oil and noticed radiator fan was not running with ac on, just pulsing.
got around to it today after cautioning her to watch temp religiously and found it not running at all.

followed the advice in the really excellent troubleshooting guide and this is what i found.

fuses all good.

fans are good. they run beautifully together high and low speed with power straight to them.

12v is present on pin 2 of the thermocouple on radiator. you can jump the pins either way and nothing.

according to this ...bad wiring if i am reading the guide correctly

my bentley was borrowed and ruined by a friend (former) who left it in the rain on the hood of his car. been meaning to replace it but have not done it yet.

can anyone post the diagram. the guide in the sticky has a link to click but looks like the picture is dead.

any advice obviously appreciated, i am working 6 straight this week and if anyone finds it in their heart to give advice i greatly appreciate it.

i am going to be driving her car so i can watch temps. so far it is great in motion at 195 or so but does roll up to about 205 at stops.havent stayed long to test whether it will get hotter.

ac works great in motion even passably at brief stops but i have been shutting it off so i dont stress it till fan is fixed.

no fan with ac on key on/ or ac on engine on

thanks for any tips. if any one has the wiring diagram for the step described that failed i will greatly appreciate it.

i ordered a fan control module since i tried to swap it to quickly eliminate the problem and realized it was a bastard to all my other ones... damn 98 beetle constantly showing me that it has to be unique.
may not fix it but i got one real cheap off the bay so i thought even if it is not the problem be nice to have a spare for the rare one and the one on the car rattled a bit when i removed it to reseat the connectors thinking at the time it was swappable with my 01 parts car.

maybe it is the problem but the walkthrough seemed to imply it would be wiring if it would not run low speed fan with 12v present at thermocouple and jumped with a fused connector which i did.

i have plenty of parts for 00-04 ones never any for the 98

i will let you guys know if it fixes that problem. not optimistic but if it is not that it is some wiring which on the new beetle is an extra joy to track.

again no fan with key on ac on. no fan with engine on ac on. seems to get warm at idle so thinking no fan period but havent sat and let it warm enough up to see if it kicks on at prolonged stop as i dont want to stress the engine.

has 12v at thermocouple, fans run great when you hook them directly to power, high and low speed. all fuses are fine. ac is ice cold when car is moving.

any thoughts from anyone who has seen this ?

and if FCM fixes it i will post it or whatever it is i find when i find it. currently kind of baffled. it was running fine as of a few weeks ago seemed to happen out of the blue.

still messing with it in my few spare minutes. never overheats but fans still not blowing with ac on.
one thing i did notice on my drives to and from work is that at idle the car seems to suddenly drop to 12.3v for like the briefest interval, the engine slightly stumbles and then it reads 13.8-14 again. this is idling with ac on fans of course not working.
wasnt sure if that was high pressure in ac system causing some hiccup as hi pressure sensor trips off and did not want to destroy my new beautiful ac compressor so i did not mess with watching for more than a few minutes and otherwise have kept car in motion when ac is on.
not sure what that is about. stays perfect in motion, and does not do it with ac off at idle. was kind of waiting on FCM to arrive so i could try that since i cant see anything wrong with the wiring at least obvious.
if that is not it i guess i have to wait for my new bentley since no one has chimed in with any ideas or diagrams. the wiring is simple but there are a few i realize i dont know where they go to.
i will post my fix when i find it. wish my wife would like a golf instead of a new beetle it is so inconvenient to work on comparatively and at 20 years old is having all the old age symptoms you would expect from a 300k mile car of that age

From DanG144 sticky:
A very kind anonymous user has generated a set of schematics for the MK IV (May99 to MY2005.) The first is one piece for easy viewing, the second is two pieces for easy printing. Thank you Anonymous.
http://pics.tdiclub.com/showphoto.ph...ematic&cat=517

http://pics.tdiclub.com/showphoto.ph...-mk-iv&cat=517

This is on the '98 NB? The early (98 and 99) ALHs do NOT turn the fans on low automatically when the A/C is switched on... they require pressure to come on, so there is a slight delay.

Sounds to me like the pressure sensor is bad, and not telling the FCM to turn the fans on. That is also likely why your idle dips... the compressor is overloading.

If the A/C cools reasonably well driving down the road at 40+ MPH, I would think the system is OK as far as charge/condenser/flow/etc. So I would look at the pressure sensor near the expansion valve. You can R&R this without discharging the system, as there is a valve under it. It just unscrews, just remove the charge air tube assembly above the belt area and you'll see it back there.

oilhammer said:

This is on the '98 NB? The early (98 and 99) ALHs do NOT turn the fans on low automatically when the A/C is switched on... they require pressure to come on, so there is a slight delay.

Click to expand...

Guess that's a difference with my late 99.5, mine runs the fans even though the AC system is currently empty

-J