Bad Temperature Sensor For Gauge??

[jdbs3]

1990 Vanagon GL

I just replaced my thermostat, thermostat housing, and the 2 sensors that fit into the housing - the black sensor for the temperature gauge, and the blue sensor for the fuel injection. The black sensor for the temperature gauge was a Meyle 87°C variant.

After the install, the needle on the temperature gauge was about 3/4 up the gauge, or 1/2 way between the LED and the max indicator. So I re-installed the old temperature sensor.

Now the needle on the gauge is on the upper side of the LED, where it should be.

So was the new black sensor to the temperature gauge bad, or ??

thanks

[kamzcab86]

[childofthewind]

It is not abnormal to have the temp gauge reading that high. Mine did that when I first purchased it. After years of work and replaced parts the needle is much closer to the led - a little below it and then the rad fan kicks on when it hits the very top of the led bulb which seems more misleading than the old reading.

http://www.gowesty.com/tech-article-details.php?id=74
_________________
1987.5 wolfsburg hardtop; 2.1

“As for me, I am tormented with an everlasting itch for things remote." - Melville

[Tom Powell]

I'm in the middle of this sensor project too. I had a bad sensor and no reading at the gauge. I replaced the sensor with a new one and got much higher than "normal operating temperature" indications at the gauge. Two needle widths above the led instead of half a needle width below and a blinking led twice. I ordered a "Made in USA" sensor from an advertiser on ebay, but it turned out to have an internal short and I put the high reading sensor back in. I now have a "normal operating temperature" at the gauge which is alarming. I'm tired of taking coolant showers under the vehicle and will live with the new gauge indications for now.

IMO The radiator cooling fan is a better indication of coolant temperatures than the sensor, gauge, or led. I have the lower temperature fan switch installed on my radiator and the fan has come on at expected times in bumper to bumper traffic. The gauge needle was nearly pegged and once the led started blinking before the fan came on. I attribute these indications to a new sensor which is "overly sensitive".

Vendors have noted on their websites that their new sensors may have higher than expected gauge readings.

I've done a similar reply in other recent posts regarding coolant temperature indications.
http://www.thesamba.com/vw/forum/viewtopic.php?t=654689
http://www.thesamba.com/vw/forum/viewtopic.php?t=627477

[jdbs3]

Thanks for all the input. Sounds like the new sensor is just more sensitive. After reading various GoWesty technical bulletins and the threads Tom Powell referenced, I've a few questions.

GoWesty noted "If you can keep oil and coolant in your waterboxer, you can’t kill it!". I'm interested in doing a road trip cross country within the next year or so, so want to understand as much as I can about the coolant system now. I've got Bentley, but it only goes so far.

So a few questions to help me along in my journey.

1. Can I confirm the sensor that read high is okay by measuring its resistance out of the van? If so, what should the resistance range be?

2. I believe my coolant system is working okay. Even with the bad thermostat (the needle would not even register with it), the coolant fan came on if sitting in stop-and-go traffic, etc.

In one of the posts, hdenter noted "They [the radiator] have a reputation for getting clogged and restricted."

How would one know if the radiator is clogged and restricted?

3. How would one know if there was an air pocket in the radiator? What would be the symptoms, and what might it result in if the coolant can not move that air pocket along?

Possibly some dumb questions, but the only way to learn.

Thanks

[dhaavers]

There is a thread here somewhere with typical resistor values for typical gauge readings...
Someone must have it bookmarked...???

Check for coolant flow through the radiator with your hand or a temp gun. Once at operating
temp, cooler areas indicate less coolant flow & that's where you are losing cooling capacity.
A new, clean rad will be pretty equal all across - top to bottom, side to side.

Air will of course tend to collect at high points...top of radiator & t'stat housing are common.
Either will prevent full flow and cause decreased cooling. Bleed carefully, watch your gauge
& keep things topped up...See you on the road!

- Dave
_________________
86 White Wolfsburg Westy Weekender
"The WonderVan"
<EDITED TO PROTECT INNOCENT PIXELS>

[Robw_z]

Just chiming in that I put in a new temp sensor as well, and it also reads high. Don't like it.

To get an air bubble out of the radiator you use the bleeder screw on top of it behind the grill. Tough to know if it's clogged without removing it. If you have overheating problems that can't be traced to anything in the rear, replacing it isn't a bad idea.

-Rob

[dhaavers]

FWIW, my new gauge sender only reads about halfway to (left of) the LED.

Whatever...

<shrug>
_________________
86 White Wolfsburg Westy Weekender
"The WonderVan"
<EDITED TO PROTECT INNOCENT PIXELS>

[Tom Powell]

[Tom Powell]

[chrisfreemanca]

[davideric9]

I bought a new Temp Gauge Sender for the 2.1 syncro part number 049919501.
Using a VOM, thermometer, pot of water ready to heat, and video camera I decided to see how the ohm resistance and temperature are related. Your results my vary (I only did this once so not completely scientific).

Here are my results

Here is my setup:

_________________
1987 Syncro Westfalia, stock (bought 1994)
1986 Syncro Westfalia SVX, 3 knob (bought 2008)
1987 Westfalia (bought 2010)
1988 Wolfsburg GL (bought 2012)

[bobbyblack]

Digging up this thread (and a variety of others, this one seems most like the title I would use to ask nearly the same question).

I recently put in a new front heater valve, a fancy version with a radiator self-bleeding function. I filled up the pressure tank and ran the engine a minute, filled more. Ran a few minutes to let it warm up. No heat coming through the heater lines, so I backed the rear up a bank and turned it off. The tank, being an aluminum version with a pressure relief lift tab on the cap was glad to let vapor out until the point I could open the cap. I put more coolant in and then started and ran the engine a bit, and the flow to the heater was restored, and also the radiator fan came on in another couple of minutes, seeming like plenty of coolant for all that.

The question I have is what failure modes have been noted with the temp 1 sensor: mine now shows a normal beginning to warm up on the gauge on the dash, it gets to the first fat white bar, then 'dies' and falls back down to the cold position. Anyone seen this kind of failure? I just wondered.

Anyway, seems there are a few Temp 1 sensors out there, Napa, Pelican, etc. but each have readings that indicate normal temp at different locations on the readout, with 'stock OE' being what I'd rather get. There seems to be a definite lack of OE sensors available.
_________________
'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[Ronkat81]

I'm with you.. my new one is giving ridiculous readings!!.

[DuncanS]

I'm having trouble finding a temp 1 sender. Everyone has 2s. A source for one which will be good?

Duncan

[kamzcab86]

[RBEmerson]

FWIW, I did the same "replace everything near the thermostat" procedure, using GW parts. Unfortunately, I have a ScanGauge, and can read T2 directly. The T2 readings are significantly higher than I recall from before I replaced the sensors. Grrr...

Using both the T1 (mostly uncalibrated needle - which stays at the bottom of the "normal" range, as it has for the 11+ years we've owned this rascal) and radiator fan behavior, I suspect T2 is lying like a rug. The challenge is to get a true reading of the coolant temp. Meanwhile, I assume all's well in the motor (hasn't seized yet!).

- - - - -

[ZsZ]

just an addon for the info above:
these senders give the variable resistor value referenced to ground - a bad ground either in the engine bay or at the gauge can mess up readings.
and the gauge runs on regulated voltage - if the voltage regulator in the dash give up the ghost it messes up readings too.
_________________
Zoltan
1.9 MTdi 2wd Multivan (ex Caravelle)
Van since 2006, engine since 2008

[RBEmerson]

A very good point!

Too often attention is paid to the "hot" or supply side of a circuit, and the return or ground is ignored. The full path, from battery to device to battery matters.
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

[SamboSamba22]

Alright guys, 20 plus threads about this issue, just happen to choose this one for my questions. 1991 Carat with 86k original miles.
Before any of my work: temp gauge always sat right on the led light or just below it at running temperature. Never any issues.

Work completed:
Stainless steel coolant pipes, new thermostat with aluminum Syncro housing, new aluminum distribution tower, GW expansion tank, new overfill tank, all new rubber hoses. Everything has been replaced for the cooling system aside from radiator (current one installed in 2021, have new one on order).

Temps at the radiator after 40 minutes idling 185° both sides, low speed radiator fan kicks on.

After 15 minutes idling, temp gauge light begins to flash. IR gun is telling nothing is getting too hot, all hoses, radiator are heating up in a normal manner. Temp gauge is sitting right on the 3/4 mark of the gauge, again light flashing the whole time. The led light does flash prior to start up and goes out.

I can’t reuse my old temp sensor for the thermostat as the original housing was plastic and the syncro unit is aluminum. I don’t recall the brand of the new temp sensor. All of the air is out of the system, expansion tank is completely full.

We leave in two days for our road trip, heading to BBB from Arkansas. The temp gauge with its flashing light is freaking me out, especially with the elevation and mountains through our trip.

Are these new sensors that sensitive/variable? Already tossed my original so no measure off of it for resistance. Of course i didn’t measure the new one prior to install.

Looking for some opinions and insight, rather new to the water cooled element of these things, any guidance or thoughts are appreciated.


Sam
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The Bus Barn Ltd. Co.

Oct. ’67 Double Cab (’68 Crew Cab)
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