Temperature Light Blinks

saa004

Active member
Joined
Apr 10, 2007
Location
Virginia Beach VA
TDI
2004 Jetta TDI (old), 2006 Jetta TDI (current)
When I start my 2004 TDI Jetta GLS and its cold outside, the temp light blinks after the engine has run a few run minutes and remains blinking. The Manual says the fluid is either low or too high. The fluid level is within the requirements (between low and high). Don't understand whats going on there. I'll turn the ignition off and start the engine again and the temp light doesn't come on on again. Does anyone have any recommendations here?

thanks
Scott
 

lovemybug

Veteran Member
Joined
Mar 11, 2007
Location
SE Wisconsin
TDI
2002 Red Beetle
I had the coolant idiot light blinking on my car and it turned out to be the coolant temp sensor. I think it's a similar part on the PD's but don't quote me on that. IMO, that's where I'd look.
 

saa004

Active member
Joined
Apr 10, 2007
Location
Virginia Beach VA
TDI
2004 Jetta TDI (old), 2006 Jetta TDI (current)
Sorry, I'm not sure what you meant by IMO. And where is the temp sensor located. I don't have a maintenance manual.

thanks
 

myke_w

Vendor
Joined
Jan 30, 2003
Location
Cbus, Ohio
TDI
03 TDI Wagon
Fluid level sender is integrated into the bottle on your car.

Try filling it to the full mark and see what happens, if it still does the same thing, I'd guess the sender is bad.
 

JPDiesel

Veteran Member
Joined
Apr 25, 2006
Location
Baraboo WI
TDI
03 Jetta Wagon 5Spd
I recently had the same problem. I checked the coolant level in the reservoir, which was fine. Then I talked to JASONTDI and he suggested that it could be poor contact in the connector to the sensor in the coolant bottle. Cleaning the connections which looked fine, did not help.

Then still suspecting the coolant level sensor, I took a small piece of 3M nylon abrasive pad in a forceps and polished the sensor bars that are visible thru the filler of the coolant bottle.

This fixed the problem. I think there was some invisible surface film on these bars that did not allow the sensor to read the correct value.
 

lovemybug

Veteran Member
Joined
Mar 11, 2007
Location
SE Wisconsin
TDI
2002 Red Beetle
saa004 said:
Sorry, I'm not sure what you meant by IMO. And where is the temp sensor located. I don't have a maintenance manual.

thanks
IMO is shorthand for In My Opinion. The coolant temperature sensor is located, at least on my car, on the driver's side of the engine, facing back toward the firewall of the car. You'll see a junction of coolant hoses there, and then something toward the back with an electrical connection going to it. That should be the coolant temp sensor. If you do a search through here, I'm pretty sure there's a procedure somewhere on how to change it. Like I said, that's what I did, and it fixed my problem.
 

saa004

Active member
Joined
Apr 10, 2007
Location
Virginia Beach VA
TDI
2004 Jetta TDI (old), 2006 Jetta TDI (current)
Ok, I'm not entirely sure this took care of it but JPDiesel, I filled the reservoir (just a little, it was way above minimum) and took a very small piece of steel wool and needle nose pliers and removed the film from the bars on the coolant level sensor in the reservoir. I started the engine and NO blinking temperature light. But, I will say the temperature outside hasn't been as cold as it was so I should know if this really was the issue when it gets a bit colder. I'll let you know if the temp light blinks again...
 

Variant TDI

Veteran Member
Joined
Mar 8, 2002
Location
SS, MD.
TDI
2002 Golf Variant, Reflex Silver
Mine used to do it whenever the temp was below freezing, but has recently been doing it as high as 46 degrees (via scangauge).

I've been frustrated by the typical responses... There's plenty of coolant there. The contacts are strong. It's a good mixture. And my temp gauge is good (again, scangauge).

Re-cycling the ignition once the coolant is above 60 degrees is the easy fix for the light, but it confuses the hell out of the scangauge, so I've just been leaving it alone to blink recently.

I am excited to try the scouring pad... It would be nice to have a real solution to this little issue.
 

lovemybug

Veteran Member
Joined
Mar 11, 2007
Location
SE Wisconsin
TDI
2002 Red Beetle
The coolant temperature sensor actually sends out two signals. One to the ECM, which is what I believe your scanguage is reading, the other actually goes to the temp guage or temp light, depending on particular model. My dash light would blick also, yet the car would run fine. Since I replaced the coolant temperature sensor, the light has not blinked once since then. I would take a closer look at the coolant temp sensor. Just my opinion, take it for what it's worth.
 

Variant TDI

Veteran Member
Joined
Mar 8, 2002
Location
SS, MD.
TDI
2002 Golf Variant, Reflex Silver
I will (thanks for the extra info), provided scouring the coolant probes doesn't work.

We'll know in a few days...
 

JPDiesel

Veteran Member
Joined
Apr 25, 2006
Location
Baraboo WI
TDI
03 Jetta Wagon 5Spd
Did this work?

I am bringing this thread back to life because I am curious if my scouring fix worked for anyone else.

Has anyone tried this with success or failure?
 

rez311

Veteran Member
Joined
Aug 2, 2005
Location
Thousand Oaks, CA
TDI
A3 TDI White
Well, if your fluid was below the mininum mark, that would explain why the coolant light kicked off... If you get the coolant idiot light again with fluid levels at normal, it's the coolant sender.
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
rez311 said:
Well, if your fluid was below the mininum mark, that would explain why the coolant light kicked off... If you get the coolant idiot light again with fluid levels at normal, it's the coolant sender.
__. Every autumn for the past three, at about the first cold snap, I'd start my car in the morning and the light would flash. Same as OP, if I drove it a mile, switched it off, and then started it again, the light would be gone and would stay off until the next morning.

__. The level in the bottle would always be normal (actually, just closer to full). I'd add 4 oz. of distilled water and the light would go out ... until the next autumn. I tried the "cleaning the contacts thing" -- didn't work (but I was wussy about it because I didn't want to overstress the contact prongs so maybe I just needed to scour harder).

__. As a result of this, my bottle has "ratcheted" up to very close to the MAX full line. But it still did it last autumn. And 4 oz. of distilled water fixed it, again.
 

SuburbanTDI

Veteran Member
Joined
Apr 5, 2004
Location
Midwest
TDI
Beetle TDI, and two Jetta TDI
I have the same exact issue with two same year, make and model PD TDI's. One silver, one dk blue. One stick, one auto.

On a cold morning light goes on, and you can drive just a block or so - turn the car off then back on - and the light will go off and remain off.

The indicator is positively correlated to the temperature. Colder days cause an issue, warmer days do not. And it is perfectly consistent, on the coldest days you will always find the light goes on.

With one vehicle I added 1 cup of water even though it appeared that the coolant level was perfect. The light went out and never came back on. Problem solved.

With the other car I have done nothing yet and the light still comes on when cold out. It does seem the dividing line for triggering it is just below freezing, but low twenties and below will always find it triggered.

Interestingly on one of the vehicles the problem began the day after Jasontdi had installed an inline 1500w coolant heater. There were no leaks and the coolant was full, but I had initially thought it was related. This occurred at the start of it's third winter. The second vehicle did not have any issue until this year, its fourth winter (This is also just after Jas, did the 100k timing service on it. :) ) . Here is my original post on the issue: http://forums.tdiclub.com/showthread.php?t=195846&highlight=coolant

My guess is that adding even just a few drops of water to the reservoir finds just enough slightly less mucked up wire to complete the circuit and send the full signal out to the light. There's probably a better cleaning aid for the sensor strip than steel wool though ...
 
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Variant TDI

Veteran Member
Joined
Mar 8, 2002
Location
SS, MD.
TDI
2002 Golf Variant, Reflex Silver
SuburbanTDI said:
With one vehicle I added 1 cup of water even though it appeared that the coolant level was perfect. The light went out and never came back on. Problem solved.
Until that part of the probe gets mucked up. ;) Your guess is right, in that you've just put coolant where it had never been, so when the signal is sent... the car sees it.

I used one of those 4 fingered "pick-up tools" and a 1" x 0.5" cutting of new scouring pad from a sponge. I didn't press super hard, but I took some time and was very thourough in cleaning off both probes.

And FWIW... I've not replaced my coolant sensor. It sends good info to the scangauge, and I've seen nothing to lead me to believe that the other, digital part of the sensor (the part that sends the overheat signal) is malfunctioning.
 
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mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
Variant TDI said:
(snip) And FWIW... I've not replaced my coolant sensor. It sends good info to the scangauge, and I've seen nothing to lead me to believe that the other, digital part of the sensor (the part that sends the overheat signal) is malfunctioning.
__. Yupp, and so many of them are bad right out of the box, changing one that works is *asking* for a crap shoot. Leave it alone if it's OK.
 

raspa

Member
Joined
Jun 7, 2005
Location
Austin
TDI
2004 Jetta GLS PD
With one vehicle I added 1 cup of water even though it appeared that the coolant level was perfect. The light went out and never came back on. Problem solved.
I was having the same problem on my 2004 Jetta. I replaced the sensor but that didn't help. I then proceeded to clean the sensor probes on the reservoir tank and added some distilled water. problem solved.
Thanks for tip.
 

Dimitri16V

Top Post Dawg
Joined
Jan 30, 2005
Location
DE
TDI
01 Golf, 04 Golf
pull the connector from the coolant level sensor and short the contacts for few days. if the light never blinks again , clean the sensor tips.
don't go replacing the temperature sensor for no reason
 

jilted

Member
Joined
Oct 13, 2006
Location
Ponchatoula Louisiana
TDI
2004 VW Jetta GLS TDI
yesterday was our first below 50 degree morning (south louisiana)
just started having this issue yesterday morning. then again this morning. first crank, alert came on, after first stop, next crank, no alert. checked the reservoir, its a little below MIN. I have had the car for 4 years and never had to add any but have fixed a few other things (new glow plug and rail, new injector harness, timing belt at 90k, etc).

so my question is: What coolant should I use? I read something about VW requiring a specific coolant.

thanks!
 
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Variant TDI

Veteran Member
Joined
Mar 8, 2002
Location
SS, MD.
TDI
2002 Golf Variant, Reflex Silver
Stock coolant (IIRC) is G12, any of the reputable online places will know. (Although if you're just adding a trivial amount, I just put in distilled water.)

Option for cleaning the coolant probes: Toothbrush. Preferably new.

__. Yupp, and so many of them are bad right out of the box, changing one that works is *asking* for a crap shoot. Leave it alone if it's OK.
At 115k miles, my stock black coolant temp sensor started getting quirky. 2 mornings ago, it thought it was -40 degrees out, and kicked me into a high idle. Replaced it with a green one, and it's all good again.
 

anar.632

Member
Joined
Dec 19, 2010
Location
Azerbaijan
TDI
2002 Jetta 1.8T
When I start my 2004 TDI Jetta GLS and its cold outside, the temp light blinks after the engine has run a few run minutes and remains blinking. The Manual says the fluid is either low or too high. The fluid level is within the requirements (between low and high). Don't understand whats going on there. I'll turn the ignition off and start the engine again and the temp light doesn't come on on again. Does anyone have any recommendations here?

thanks
Scott
I have exactly the same problem in my 2002 Jetta 1.8T. U wrote this Thread a year ago. So i Hope ur problem had been solved since now. So what was the problem. how did u solve it?
 

tda2007

New member
Joined
Sep 3, 2011
Location
Fairfield, Iowa
TDI
2001 Beetle TDI, 1985 Golf
I actually prefer Howes myself. However, Stanadynes bottles are much more convenient so I actually refill them with 8 oz of Howes. Then I just dump the whole bottle in instead of having to mess with measuring it out at the pump. Frost heater makes a little homemade kit with 4 bottles plus gloves in a container. You could obviously do it yourself the same way but it's nice that he put it together. I just wish Howes sold 8 oz bottles...
 

airportex

New member
Joined
Dec 19, 2017
Location
ME
TDI
2014PassatTDISE
I thought I'd revive this because I was relieved to find others who had battled with this issue and were still alive and well. My 2007 Rabbit just now, 8:08 pm, 12/27/2017, 10 degrees F, responded with a blinking temp light when I started it. Despite a comfortably full reservoir and a temp gauge showing 120 degrees +or-, it is blinking. I will try the suggested tips and let you know how I made out.
 
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