Sensor is my guess

 

I'd guess the sensor, especially if you have a B5 with the old, bad senor unit. However, it is tough to be sure. Since the sensor is easy and cheap to replace, you might was well try it, and then go from there.

SirWired

 

I recall reading other posts that state there are actually two temperature sensors. One sensor is for the gauge, and the other is for the engine. So it just may be the gauge sensor. And if not, just make sure to check/change both.

 

I recall reading other posts that state there are actually two temperature sensors. One sensor is for the gauge, and the other is for the engine. So it just may be the gauge sensor. And if not, just make sure to check/change both.

There is only one sending unit that houses the two independent coolant temp sensors.

 

It is the sensor.
even if it isn't the sensor, the sensor is an easy and cheap fix so do that first. The thermostat takes quite a bit of time.

 

Could be either. Do you have climatronic? If so, as long as coolant stays at 120*F, the climatronic will regulate the flap to provide enough heat so you probably won't notice loss of heat in the cabin. If you have manual a/c then turn temp dial all the way to max. temp and see if you notice any change in air temp out the heater ducts when the temp drops to 120*F or so vs. the 190*F. Usually, when the sensor begins to fail the gauge will fluctuate between 0 and 190*F or some other values in between regardless of engine load and coolant temp.

 

Thanks for the response-- I'm going to try out the sensor first.
Just fyi its a 1999 AEB engine- turbo-four tip/ manual HVAC. 176k..ultimately- nothing has gone wrong with cooling/heating/gauges until now.. there's always first for everything i suppose.

Here's another thing that i noticed- i went back to my car for my lunch hour turned the engine on-- set the heat to high (set it at idle for a couple of minutes, drove around the lot (mall, say a mile)- the heat was up in the cabin- but the temp gauge was barely at 2nd bar. I then shut it the engine off, then turn the accesories only- and the needle shot up to 190* (just below) .

i'll put the order in for a sensor today and take it from there then.

 

Speaking of the temperature sensor:

It's my understanding that the temp. sensor with the BLACK connector is faulty by design, but my car has the temp. sensor with the BLUE connector. Do I still need to replace it with a new sensor with a GREEN connector, or am I exempt from that particular problem?

I also have a 1999 AEB.

 

^ funny, I was just wondering the same thing, the blue / green sensor depends on your VIN. Pre 3B-X-491580 have the 078 919 501 B (blue) and post 3B-X-491581 have the 059 919 501 A (green) sensor.

My VIN is 3B-X-424190 and I have the blue one, this will be fine since it's not the faulty black sensor.

 

My VIN is 3B0XE181841. I guess that means I'm supposed to have the blue sensor.

 

it is my understanding that green replaces black and that blue replaces blue. The connectors are different so if you did a blue instead of a green or visa versa you would also have to splice the harness. ECS has some picture up so you can take a look.

 

Vag-Com it to see if you get any error messages regarding
the temp. sensor. Or just replace it anyway. Those things go bad
so often it should become part of scheduled maintenance.

I would probably just replace the temp. sensor at this point.
Besides, my A4 exhibted the exact same problems and it
did indeed turn out to be the sensor. If it's not the sensor
then.. it's your thermostat going and you'll need to replace it.

 

They go bad that often, eh? Even the non-black ones?

 

Not to hijack, but is normal operating temperature always 190-degrees? This is my first VW... if I'm driving around town, my 1998 AEB stick shows 190* but on the highway it falls back to the first mark to the left of 190 and stays there...

My previous car (GM) would get to its mid-point of 220* and stay there regardless. I thought an engine not running "at temp" usually meant lower gas mileage. Should I replace my blue sensor? Or is 180* (or whatever the mark below 190 is) okay?

THANKS ... learn something new on here every day =)

 

The temp gauge is basically a cool looking idiot light. If after the intial warmup, the needle moves at all away from 190, you got something wrong.

 

THANKS AGAIN ALL FOR THE RESPONSE... i'm just waiting to get the Sensor and i'll let you all know how it goes.


e

 

***********update****************
Got the sensor today - I went ahead and purchased it from VW (along with a new left wheelwell liner, and new W8 belly shield) Igave the sales person my last 8 Vin number and he gave me the Green Sensor. After i got the car to cool down after getting home, i removed the sensor (beleive it or not, i wasnt sure where it was located, but i was able to figure it out (behind the engine , near the firewall) Took the ''blue'' connector (which was a perfect fit to the new sensor) and removed the retaining clip and popped the old one out. OOPS!! i should have placed a towel underneath because a good amount of coolant spilled out. The old sensor was Blue, and the whole metal nipple was tarnished badly to dullness. Popped the new one in, placed the retaining clip back and Turned the key to on, then shut down, then turn it on again (yah its a weird thing i do after working on my car disconnecting stuff, Its sorta like a manual reset) turned the engine on, and let her idle for a minute, then took off for a 4 mile drive. The temp gauge creaped up to 190* in a short time and stayed there through the duration of the drive. I also drove out 30minutes later to drive out to BestBuy (8 miles rt) and the temp gauge creaped to 190* like normal and no more fluctuation!!!
Thanks to all!!!

 

Good. When mine went out on my sedan, the temp would drop all the way to cold.

BTW, the thermostat is pretty easy to replace in the AEB/ATW.

 

pz,

COOL- thanks-- where exactly is the thermostat? the last two times they were change, i wasn't present (1st was via dealer- warranty, 2nd was independent vw specialist shop-preventative maintenance-ecs kit).
im sure it is fine at the moment (gauge working well today on a 31 mile ride to work at 52* this morning. Gauge stayed at 190*.

e

 

Tip,

Is the location of the sensor easy to find once you look in the rear of the engine area?

Thanks!

 

luvmypassat,

Yeah- right at the back of the engine- near the firewall there is a bunch of wiring wrapped in black vinyl-and at its end is a blue connector that is plugged in at the back of the engine block- You should be able to pull that plug (If you already have the spare sensor with you- you will see that the plug will fit over your new sensor.)
Upon removal of wiredplug- make sure to remove the retaining clip (it's like a lip that is potruding out along the rim where the sensor is sitting) i had to use the flat edge of a screwdriver to pry it off (dont break it! if you dont have a spare!) You may want to put some kind of a towel catch underneath (i had spillage of coolant when i pulled the sensor off).
the temp gauge has been performing as it should be today. thank goodness it is nothing too serious!

e

 

The Thermostat on the AEB/ATW is under the water pump. From under the car, (after removing the belly pan) follow the lower radiator hose up and you will see it connect to a flange with 2 bolts. The large bolt to the side is the coolant drain for the engine. There is a bracket in the way, remove that and then remove the 2 bolts holding the flange. I leave the hose connected, but it can be removed. Replace the thermostat and O ring. Sometimes the thermostat will fall out before you can replace the flange, so it may take a few tries.

 

Isn't there a recal of the temp sensor? I got a letter about it and now mine is doing exact what yours is doing. I was thinking of taking it to the dealer, but I don't want them to charge me a diagnosis fee. How much was the sensor?

Kevin

 

sensor is like under 10 bucks

 

Sensor costs more like $30 at the dealer nowadays. For a while the green sensor was selling for $5 at the dealer. Oddly, my $5 green sensor died after a few year.

There is no recall on the sensor. The warranty on the component has been extended to 100k miles. It only applies to the 1.8T, which is odd because the V6 has the same part and suffers from about the same failure rate.

 

Hi!
I´ve read a couple of threads about the G62sensor and I still haven´t found anoyone who has the same symptoms as me. My car runs great, no problems with starting the car when it´s warm. At first my temp gauge showed either 0 or 90 (degrees celcius, I´m from sweden). I read about this faulty temp sensor and replaced it. Now the temp gauge always work but still it acts strange. When I first start the car the temp gauge slowly raises, until it has reached 66C (the mid position of the gauge). There it stays for about 5minutes, and then suddenly it goes very quickly to normalposition (90C, 190fahren I think). Then after 1minute it suddenly drops to midposition again, and then after another minute it goes back to 90. Then it can drop again randomly. I have used vag-com to measure the value from the sensor to compare the gauge to computer value. The gauge and the value are equal until the gauge/computer value reaches 66C. When the gauge suddenly moves to 90C the value in the computer stays at 66C. After another 5minutes the value in the computer starts moving again. 20minutes after the computer value showed 66C it now shows 85C. So it moves veeery slowly! Is there anoyone who have had a similiar problem?

Sorry for all the text, it´s just my bad english.

Very thankful for answers!
/Linus

EDIT: My car is a passat 1.8t -99

 

Linus, you probably have a bad sensor. Looks like your replacement failed as well. The gauge and the ecu sensor are on different circuits within the same device, and can fail independently of each other. Your vehicle drives fine because the ECU part of the circuit is operating normally.

The two times my sensor failed, it was only the gauge circuit that failed. It would fail consistently at particular temperatures. The ECU circuit was fine, so driveability was unaffected.

As you can see here, I'd lose signal completely at specific temperature points. This was consistent:

 

Hm, okay. But the thing is, I replaced it again today (even though the first replacement was only a month ago). Still the same symptoms! :banghead: I find it hard to belive that the "gauge-part" of the sensor fails in both the new sensors!? I have also checked the cables and I think they look fine. I´m gonna replace the thermostat tomorrow, even if the symptoms aren´t general for faulty thermostats! I´ll give you the result tomorrow!