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gomi_otaku
gomi_otaku, VW Technician
Category: VW
Satisfied Customers: 3378
Experience:  VW FastTrack '00-'01, VW Academy Chicago and Seattle '00-present, VW Certified
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We have a 98 vw new beetle. the red light flashes- the fuses

Customer Question

we have a 98 vw new beetle. the red light flashes- the fuses look good and no melting of fuse compartment we replaced the fans- both certified working.. we replaced the temp module- jumped it and fans came on. we replaced the thermal sensor on bottom of radiator. The fans still do not run. Any suggestions
Submitted: 1 year ago.
Category: VW
Expert:  AZTechBrian replied 1 year ago.

Hello. I am sorry to see nobody has answered your question for so long. I just logged on and noticed your question and thought I would reply since earlier this year we had the same exact issue on a 98 VW new beetle and the problem was the cooling fan control module. It is not an uncommon part to fail on these cars. It is however important to replace it with an original VW part. There are aftermarket modules but when we had this issue we used an aftermarket and it lasted only a couple weeks and came back with the fans now refusing to turn off and killing the battery. We replaced that one with an original VW module and it is still working great. I have attached a picture of the module that I am referring to. Is this the part that you have replaced?

Customer: replied 1 year ago.
This is the part we replaced. When we jump it, the fans come on. The top and bottom radiator hoses are hot so we don't think it is the water pump. We did get an aftermarket, but is there any way to make sure that is the issue?Can voltage be tested?
Thank you for getting back to us
Customer: replied 1 year ago.
Sorry, just checked with my husband...we jumped the thermo switch..located on the bottom driver side of radiator...sorry if that was not clear.
Expert:  AZTechBrian replied 1 year ago.

I don't think the problem is the water pump either. Do you have a diesel or gas engine? I apologize if you provided that information earlier, but it's not showing up for me.

Customer: replied 1 year ago.
Its a 2 liter gas engine stick shift...if that makes a difference...
Expert:  AZTechBrian replied 1 year ago.

Ok. It only matters for checking TSBs. You have replaced the thermo switch and the module that I have pictured? What exactly have you replaced? I just want to make sure I know all the details. If you have not replaced the thermo switch then I would like to walk you through testing it to see if it's bad or not. If you have replaced it, then I wont put you through that. Although I suspect the fan control module is at fault, it could be the thermo switch and unfortunately the fan control module has no direct testing, so we need to rule out other possibilities to be sure it's the fan control module.

Customer: replied 1 year ago.
This began with the car flashing red temp...we looked and fans were not running..car was hot so when it cooled down we added fluid and started it. no fans..red light came on within 5 min of engine idling. We checked fuses on battery and #16 in car... all look fine... We tested fans and only one seemed to be good...so we went to parts place(used) and got two replacements. They are verified working.... the fans did not help the original light...we then suspected fan temp module...so we ordered that and when it came, we switched it out. Still no farms... w jumped the temp sensor on the radiator and the fans worked.... so then we suspected that thermal sensor in radiator....so we then changed the thermal sensor on the bottom of the radiator... still no fans...what a bite! we saw there are other sensor type things..a thermal switch ( white something with ac) We heard about the issues with fuses and water pump...... We are just trying to get this little guy going again because he is a great car to drive to work! I love it!!Thanks again for trying to help..in Michigan it is now 11:47pm..I will check this again in the morning..
Expert:  AZTechBrian replied 1 year ago.

I understand.. We will do what we can to get the little bug back in order.

Alright, so you have verified that the cooling fans are in fact functional by directly applying power to the fans and saw them run..

You have replaced the thermo switch located in the bottom left of the radiator, so we can rule out a bad thermo switch, so testing it at this point really isn't indicated.

There should be a red wire at the thermo switch, check to see if that has power. It should.

If it does have power then I am going to put my bets on the fan control module, but just to be sure, when you say you replaced teh fan temp module, are you talking about the module that I sent you in that picture?

When ever you get back to me is perfectly fine.. no rush.

Customer: replied 1 year ago.
I should have said..yes that is the module we are referencing..it receives the two pigtails one from the battery and the other going to the fans. The difference is ours was after market but the number...that #919506K is the same.I just made sure with my husband..that is the red wire he was checking when he jumpered it to make the fans come on. He works with DC power so electrical is his baby..He did go on line to see if a VW dealership has the VW module in stock..everything was closed last night but he will be looking to get one today. Just for conversation....and future repairs.. (we have three bugs..mine and both our daughters drive them.) do you know what the difference could be?(aftermarket vs dealer) we have used after market pieces quite successfully in the past on other vehicles. Why are these bugs so sensitive?
Expert:  AZTechBrian replied 1 year ago.

I think the issue with aftermarket is more of a quality issue. I have installed the aftermarket module only to have it go bad after a short time. I would think if you installed an aftermarket part, it probably would have worked at least for a little bit. If the behavior of the fans is exactly the same with the new module as it was with the old module, then it looks like the module is not the problem. I am going to opt out. hopefully one of the other techs knows what is going on and can get your fans working again. With everything you have tried, I am at a loss at the moment.

Expert:  gomi_otaku replied 1 year ago.

Have you actually tested the water pump to make sure you have flow? Just disconnect the small line at the coolant overflow reservoir, point it into the top of the reservoir, and have someone rev the engine to about 2000rpm. You should have steady flow with no excessive ai or spitting, and it should increase with rpm. The water pump on these is notoriously bad, it will break into pieces, or it will simply crack and may flow a little but will mostly spin on the shaft. You could have hot hoses just because the engine is getting overheated.

Also, the strip fuse block on the battery- did you pull out and check all the green 30 fuses there? They will often melt down without blowing. Check the thick wire from the positive terminal to this fuse block to see if it is discolored due to heat.

Customer: replied 1 year ago.
We did not visually check the pump but we can do that tomorrow. My husband is at work and I am at work. Tonight he will be at school so we will not be able to work on this bug until Tuesday. He did order the module from a dealer and it should be in Tuesday as well.Would the water pump cause the fans not to run? This is what is happening. Our fans are not going on at any point-- even if the AC button is pushed- we do not have fans. We forced them on by jumping the thermo sensor--We did check the 3 fuses on the battery and the #16 fuse in the car compartment. They do not show any melting or discoloration. That was one of our first checks. They don't have corrosion--- they look ok. I will recheck them tonight when I get home. (I can do that on my own.) We do have power because when the thermo sensor on the bottom of the radiator (drivers side) was jumped the fans came on. My husband also checked one of the pins in the fan module and had power.should we still check the water pump?
Expert:  gomi_otaku replied 1 year ago.

OK- if you can turn on the A/C switch and the fans will still not come on, then you have an issue for just the fans. And you said jumping the temp switch at the radiator you were able to get the fans to kick on. I would suspect the fan control module under the frame rail then. Check for battery positive on the red power wires, check and clean up your grounds since you are under the battery area.

Customer: replied 1 year ago.
ok.. will do when I get home. I will let you know if there is a change. I leave work about 4:45- it is 3:13 now.
Expert:  gomi_otaku replied 1 year ago.

Ok, no hurry

Customer: replied 1 year ago.
Last night I did inspect the wires from the fuses. There was no discoloration of wires, connectors, and no corrosion on the top where they hook to wires. I did take them apart and cleaned the connectors and nuts. No difference in fans. I also unhooked and rebooked the battery and cleaned those posts too. My husband will be picking up the new VW fan module today. This is really a bummer... Any other suggestions?
Expert:  gomi_otaku replied 1 year ago.

I would make sure to check the coolant flow, just to make sure it is OK. But it sounds like your issue is with the fan control module under the frame rail (under the battery area)

Customer: replied 1 year ago.
Last night my husband came home with the VW fan module...the picture is attached.. he put it in and..... no fan...this is really beginning to suck! I will check flow tonight with my son... any other things I could try? thank you... I really do appreciate you trying to help!!
Customer: replied 1 year ago.
Ok.. we did test the water pump, as you asked, and it is not circulating... we will order one today. Can you tell me how that effects the fans? is it the sensor in the radiator? That is a sensor that tells the fan to start?? correct?
Expert:  gomi_otaku replied 1 year ago.

Yes- so if the pump is not circulating coolant, those hoses will get hot just because the whole system is getting hot. But the thermostat will not open, and the fans will not kick on.

Customer: replied 1 year ago.
Thank you..we will be putting that in Friday after work...if it's ok, I will let you know how this goes. Thank you again!
Expert:  gomi_otaku replied 1 year ago.

OK- the pump is driven by the timing belt, but I have been able to replace it without having to completely remove the timing belt (though it is tricky. So I would make sure to set the engine up at Top Dead Center in case you lose your timing references with regards ***** ***** belt.

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