Flashing Coolant Lamp/Chime, AC blows warm

Moonlight · Jun 10, 2013

2002 NB 5 spd with 80K miles. Car has been perfect until a few days ago. Started getting intermittent coolant lamp/chime and now it's progressed to the point where lamp flashes continously and chime every 15 seconds or so.

Coolant level is fine, no codes. As soon as I turn key on, engine not started ... I noticed the fans turn on and run. Fans continue to run once car is started and never go off when engine is running (this is with engine cold or hot). I have never noticed the fans running on the car, ever until now. Also just realized AC blows hot air ...was ice cold a few days ago before this happened.

Pretty sure coolant is circulating in res. bottle as I can see pink in the plastic fitting the hose attaches to ...and it goes clear if I pinch the hose.

Stumped.

Moonlight · Jun 11, 2013

Anyone? Bueller?

fierodough · Jun 11, 2013

Sounds like your temp sensor is kaput... Do you have vag-com?

Moonlight · Jun 11, 2013

I think there is more than one 'temp' sensor depending on which one you are talking about. I know FCU is fine since fans are running. Weird thing is the low coolant light/chime deal ...and now fans/no AC issues all occured around the same time frame. Everything worked fine last week and now blinking low coolant/chime ... and fans run on high with key on AC off ...and AC blows hot air.

Yes, I have a VagCom ... per my reference to 'No codes' set.

Thanks.

fierodough said:
Sounds like your temp sensor is kaput... Do you have vag-com?

gforce1108 · Jun 11, 2013

Use your VCDS to see what the ECU thinks the temp is. I assume your 02 doesn't have a gauge, correct? Just the Blue/Red coolant light? The flashing red light also means overheat on a beetle if I remember correctly, not just low level.

Moonlight · Jun 11, 2013

My 02 and 04 both have the lamp, no gauge. On the 04 it's always blue when cold ...acts normally. The 02 has always been out entirely ...no blue when cold. Not sure if there is a difference between years.

The coolant light on the 02 flashes when engine is bone cold so I know the engine is not overheated.

I'd gladly use the Vagcom to read temp if I knew where it's located. Sounds like ECu is being told engine is overheated and ECU is shutting down AC? Would like to have a general idea to what I should replace rather than easter-egging parts.

Already ordered a new coolant bottle just in case as that was cheap.

Moonlight · Jun 12, 2013

Doesn't look like anyone has any definitive ideas as to things to check. Guess I'll have to take to a shop to have diagnosed. I've checked the obvious things like fuses, since fans run FCU must be good. Will install a new coolant bottle today however I doubt that is the culprit. If not will take to stealership.

Vince Waldon · Jun 12, 2013

Moonlight said:
Doesn't look like anyone has any definitive ideas as to things to check.

This is an idea that's already been offered... it's a good one:

gforce1108 said:
Use your VCDS to see what the ECU thinks the temp is.

...and aligned with your thinking that the ECU will disable the A/C if it thinks the engine is overheating.

A quick visit to Ross-Tech's site (or a bit of searching here) should quickly tell you what measuring block(s) to check...and what you're looking for is a completely implausible temperature signal.

Or just shot-gun the coolant temp sensor.. they are a common fail item and pretty cheap.

Moonlight · Jun 12, 2013

I went thru all measuring blocks last night and any/all that displayed a temperature indicated 41 Celcuis shortly after engine was started cold. 105 F didn't seem out of the norm to me. Based on a lot of reading it seems the temp sensor sets a code most of the time ...and I have no codes. May try switching it out on a chance ... Would have thought someone, over the last 12 years would have had this precise problem. guess not.

DanG144 · Jun 12, 2013

Read the temperatures in the engine controller Measuring Value Block 007 after the car has sat overnight, before cranking. Do they all read about the same?

Now go to the instruments module, and read outside air temperature, ambient air temperature, (sorry I do not know the MVB) and the engine coolant temperature (which is a different sensor [though in the same housing] than the one in the engine controller. Do they read the same as the others?

Now run the engine until it is hot, and read the sensors. Do they all still make sense? Log the sensor output temperatures into a .csv log, and see if one or more is erratic.

You cannot take a snapshot, and say everything is fine, when you have clear indications of an intermittent problem.

AC and Fan troubleshooting.

Look for the pdfs in the first post for troubleshooting details.

Moonlight · Jun 12, 2013

That is precisely the group I was referring to primarily. I can tell you now before starting the car yesterday they all read right around 41 C.

I'll see if I can read the other stuff assuming I can find the correct blocks to read, etc.

The problem is not intermittent any longer. Fans on high as soon as key is turned on ... every time. Red coolant light/chime blink after about 15 seconds starting car cold ... and continue to flash/chime every 15 seconds or so until car is turned off. AC blows hot air.

I downloaded the .pdf's a few nights ago. Haven't had time to read all the way thru them but have checked the more obvious things (fuses, relays, etc.). And I know my fans work ...they just come on high instead of low and run continuously

DanG144 said:
Read the temperatures in the engine controller Measuring Value Block 007 after the car has sat overnight, before cranking. Do they all read about the same?

Now go to the instruments module, and read outside air temperature, ambient air temperature, (sorry I do not know the MVB) and the engine coolant temperature (which is a different sensor [though in the same housing] than the one in the engine controller. Do they read the same as the others?

Now run the engine until it is hot, and read the sensors. Do they all still make sense? Log the sensor output temperatures into a .csv log, and see if one or more is erratic.

You cannot take a snapshot, and say everything is fine, when you have clear indications of an intermittent problem.

AC and Fan troubleshooting.

Look for the pdfs in the first post for troubleshooting details.

DanG144 · Jun 12, 2013

Since you have a red coolant light and chime, the chances are VERY good that you can find the problem, or at least A problem with VCDS.

After looking for fault codes in the engine and Instrument controllers, do an AUTOSCAN.

Do you have an owners manual? What does it say that the red coolant light flashing and chime mean? If you don't have one, ask other beetle owners.

Moonlight · Jun 12, 2013

It means low coolant level. new coolant tank just showed up and I'll probably fill with water and plug it in to see if anything changes. Initially the coolant light/chime was the only thing wrong ...then noticed the fan issue a few days ago. Not entirely sure if fans went snake chit at same time as coolant light/chime and want to think I would have noticed fans running earlier but who knows at this point.

On wife's 04 NB PD ...with 230K miles everything works perfectly ...go figure. I guess I have a car to swap parts with if needed to a certain degree.

Vince Waldon · Jun 12, 2013

If the car thinks it's overheating it will:

- flash a red light on the dash
- disable the A/C
- run the fans on high, continuously

I count "strike three!" on your 15 buck coolant temperature sensor. Just sayin'.

It will *not* throw a code if it thinks the car is overheating... that's a "normal" condition for the sensor to see.

Having said that, I vaguely remember some Beetles have a separate coolant sensor for the A/C... but I'm pretty sure that was the 1999.5 model.

Moonlight · Jun 12, 2013

Does sound like the logic thing to try first. I'll order one or see if my cousin has one or can get one thru his Napa store.

Vince Waldon said:
If the car thinks it's overheating it will:

- flash a red light on the dash
- disable the A/C
- run the fans on high, continuously

I count "strike three!" on your 15 buck coolant temperature sensor. Just sayin'.

It will *not* throw a code if it thinks the car is overheating... that's a "normal" condition for the sensor to see.

Having said that, I vaguely remember some Beetles have a separate coolant sensor for the A/C... but I'm pretty sure that was the 1999.5 model.

BobnOH · Jun 12, 2013

You can try checking/cleaning the sensor in the coolant bottler, but I really don't see that kicking the fans on. Also look to see if the fuse on top of the battery are cruddy

vdubspeed · Jun 12, 2013

straight water will not make the connection as it should. Jump the two pins at the coolant tank to please the cluster. The wire is purple/black I believe

Also..suspect corrosion in FCM. Just clean the contacts.

Report back.

Moonlight · Jun 12, 2013

BobnOH said:
You can try checking/cleaning the sensor in the coolant bottler, but I really don't see that kicking the fans on. Also look to see if the fuse on top of the battery are cruddy

Already checked all fuses, etc. a few days ago. All good, clean, no corrosion.

Will know about coolant bottle here in a few minutes as soon as I can break a way from work for a few minutes. I doubt it's the problem though considering the fans are involved.

Moonlight · Jun 12, 2013

Just remembered seeing a receipt from original owner when I bought the car last year as it's was a one-owner car with all history. Found receipt for 12/2007 when car had 49K miles on it. 'Replace Engine Temp Sensor' due to codes P0128 P0118 to the tune of $144.87.

Looked and sensor has green around it ... so it's not original and has 30K miles on it.

gforce1108 · Jun 12, 2013

newbeetle.org is not the most technical forum, but there is some useful information for the oddities found on the beetle:

Blue coolant light = engine cold
Flashing blue coolant light = fault in the coolant monitoring system
Flashing red coolant light = low on coolant
Steady red coolant light = engine overheating,

As mentioned by someone earlier - the older beetles had a second sensor (switch) installed in one of the radiator hoses. I do know that it will interfere with the AC working but I don't know what years they were found on. I have only worked on two TDI beetles, both 98s.

Moonlight · Jun 12, 2013

Put paperclip in coolant res. plug ...no change.

Think I found a clue ... in VagCom after engine started/running for a few minutes.

In Instrument controller, group 3 ...block that says "Coolant Temp" reads 122 C and toggles between 122 C and 130 C. This is around 250 F ... That's the one that seems fubar.

Engine controller, group 001 block 4 temperature reads 58.5C

group 7:
block 1 (temperature): 24.3C
block 3 (temperature): 25.2C
block 4 (temperature): 59.4C

Moonlight · Jun 12, 2013

gforce1108 said:
newbeetle.org is not the most technical forum, but there is some useful information for the oddities found on the beetle:

Blue coolant light = engine cold
Flashing blue coolant light = fault in the coolant monitoring system
Flashing red coolant light = low on coolant
Steady red coolant light = engine overheating,

As mentioned by someone earlier - the older beetles had a second sensor (switch) installed in one of the radiator hoses. I do know that it will interfere with the AC working but I don't know what years they were found on. I have only worked on two TDI beetles, both 98s.

don't see any switches/sensors in any radiator hoses ...

BobnOH · Jun 12, 2013

Unless the car is really overheating, I think you found your problem

BobnOH · Jun 12, 2013

Moonlight said:
don't see any switches/sensors in any radiator hoses ...

I think those were'98-'99, mine has it

Moonlight · Jun 12, 2013

BobnOH said:
Unless the car is really overheating, I think you found your problem

At the risk of sounding like an idiot ...are you are implying coolant temp sensor? Was just replaced 30K ago ... and would also imply the other readings in vagcom in the engine controller are getting temps from another sensor?

Vince Waldon · Jun 12, 2013

He's saying you have a sensor that's reporting a temp of "boiling"... and unless your car is actually boiling you've found your problem.

Regardless of when it was last replaced.

BobnOH · Jun 12, 2013

I was just reading this-
In Instrument controller, group 3 ...block that says "Coolant Temp" reads 122 C and toggles between 122 C and 130 C. This is around 250 F ... That's the one that seems fubar.
Whichever sensor is reading 250 is malfunctioning (or the car is super hot).
Check the notes on Group 7 in this post

Moonlight · Jun 12, 2013

I understood the high temp indicates it's wrong but not necessarily clear the value comes from the coolant temp sensor.

The Engine controller Group 007 values seem correct, of which the last value is engine coolant temp.

Group 007 (Temperatures)

Fuel Temperature
Nothing
Air intake temperature
Engine coolant temperature (see my previous post - where it's reading 59.4C on my car after it's been running for a few minutes)

The reading I'm seeing of 122-130 C is not coming from the Engine controller, it's coming from the instrument controller, thus the question I had/have is what sensor is giving me the 122C reading in the instrument cluster since Engine Coolant temp in the engine controller appears to be correct?

If it's the coolant temp sensor that's already been replaced great, I'll replace it but it's not clear to me

Vince Waldon said:
He's saying you have a sensor that's reporting a temp of "boiling"... and unless your car is actually boiling you've found your problem.

Regardless of when it was last replaced.

DanG144 · Jun 12, 2013

The single housing for the coolant temperature sensor has two separate sensors in it. One for the ECU, one for the instrument cluster.
Any time they differ, replace the unit.

Moonlight · Jun 12, 2013

DanG144 said:
The single housing for the coolant temperature sensor has two separate sensors in it. One for the ECU, one for the instrument cluster.
Any time they differ, replace the unit.

Got it, thanks. Will replace tomorrow and go from there. Not really sure why the circuit that sends coolant temp to cluster would cause the fans/AC to go bat chit ...when the other 1/2 of the sensor seems to be reading fine. Time will tell.

Flashing Coolant Lamp/Chime, AC blows warm

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