VDO oil temp sender problems

[autokunst]

This is not an E9 or E3 topic, but the VW forum (The Samba) is harder to get good technical feedback whereas this group is amazing (thank you)!

We're trying to add an oil temp gauge to our 2,180cc powered 1967 Beetle. I bought a VDO temp sender with M18 x 1.5 threads to use in the oil relief port. Before installing, I bench tested it and it does not provide the correct resistance readings. It actually drops out (no resistance, or all resistance) at around 160 degrees Fahrenheit. It is supposed to read 120 degrees to 300 degrees. We bought a second one. The resistance readings seemed better, but it drops out at about 180 degrees. Boiling water will not read (the gauge just drops back to zero (or 120).

Has anyone else had issues with these VDO gauges? The two we bought (we're $100 into this affair) were made in the Czech Republic, and we bought them from two different sources. I can't believe that we were lucky enough to buy two defective units. Are we doing something wrong?

For the record, I've read that these senders should provide 323 ohms at 120 degrees and 18 ohms at 300 degrees Fahrenheit. It may not be far off at 120 degrees, but they go out completely well before 212 degrees (boiling water). The model is VDO 323-064.

 

[Stevehose]

You have the correct pairing of sender and gauge?

 

[autokunst]

You have the correct pairing of sender and gauge?

The best answer I can give is "probably". Both are intended to read/show 120 to 300 degrees F (actually 50 to 150 degrees C). And both are sold together by some sources. What gets me is not the chance of a mis-calibration (which I suspected could be the case and is why I'm testing the combination), but the fact that the sender has what appears to be a linear change in resistance all the way from about 1,000 ohms at room temperature, then a slow reduction as the sensor heats up: 900, 800, 700, 600... It gets down into the 300s as the water is starting to get pretty hot, then around 260 or 270 ohms, the meter screen reads OL (which is out of limit). I'm not sure if it drops into high resistance or low resistance, but this is only in the neighborhood of 200 to 212 degrees, and the sensor is advertised as reading up to 300 degrees (150 Celsius). It is curious.

Another thought is that my boiling water method is somehow ruining the sender due to the water/vapor. But I'm not sure about that. I mean, it is intended to live under a car that would be driven in the rain. So it should handle getting wet. Plus, the results are repeatable. If I let the sensor cool down, it will suddenly read correctly again when it reaches 180 F (or 160 F for the first sender). Then I can run it back up to OL...

 

[Arde]

OL should be infinite resistance.
I would check by heating oil instead of water...and make some french fries while at it .

 

[JFENG]

Long shot but try it with just then end of the sensor in the water (eg the spade connector etc above the water). Maybe the water is shorting out the resistance between the spade and the sender body.

 

[autokunst]

Long shot but try it with just then end of the sensor in the water (eg the spade connector etc above the water). Maybe the water is shorting out the resistance between the spade and the sender body.

Hi John,
Will do. While I don't think that is the issue, I do want to run that idea to ground (not literally "ground" - ha ha). It would be great to be able to more accurately replicate the actual installation condition.

 

[autokunst]

UPDATE:
I spoke with VDO tech support. His opinion was:
- there is no issue with my boiling water method. The sender should handle that just fine, and
- He thinks I have two bad senders. Evidently we bought these from two different sources, but neither one is an "authorized" VDO dealer that would have initiated a 2 year warranty.

I've ordered a 3rd sender from an authorized dealer, and will try to return the other two.

I also tested the first two in the oven versus in boiling water. This test scenario is dry, and also allows for higher temps than boiling water. Unfortunately, the senders failed again at some point before they reached 250 degrees F (remember, they are designed for 300 degrees). The heat developed slower with this method and I could really see the sender fail. After failure, it started to cool down. The meter bounced around between open circuit and very low impedance (.5 to 1 ohm) for about 20 or 30 seconds until it finally jumped up to about 120 ohms and started to climb in a linear fashion. Again, this was all well below the rated range of this sender.

I can't believe we ended up with two bad senders, but hopefully the third one from Summit Racing (an authorized VDO dealer) will be a winner. If not, I am told bad things happen in threes.

 

[Stevehose]

I can't believe we ended up with two bad senders

counterfeit?

 

[autokunst]

Interesting theory. I just hope the next one is legit.

 

[autokunst]

Writing with an update. The THIRD VDO oil temp sender arrived today. And to our surprise, IT WORKS! The test methods were the same as before - that was never the issue. Rather, we actually ended up with two bad senders. The VDO technical support person was right. This time we ordered it from an "authorized dealer". I will not mention the other unauthorized sources - one of them is quite popular with the bugs.

We're hoping to return the two bad ones for full refund. This will be installed in the car tomorrow. Glad to put this behind us. Thanks for all the comments and suggestions.

 

[lip277]

Makes me wonder if the non-authorized dealers were selling 'real' VDO parts or....????

 

[Arde]

How to deal with the unauthorized dealer that send the wrong senders? Are they in hot water?

 

[sfdon]

Simple question- does the sender state where manufactured?

Don’t buy Chinese junk…

 

[autokunst]

Simple question- does the sender state where manufactured?

Don’t buy Chinese junk…

All three were stamped Czech Republic.

I cannot speak to whether two were "counterfeit". But two were stamped 923 and the other (good) one was stamped 723. My current theory is that this stamping is a date code, maybe July was a better batch than September? Don't know. Just happy that we're getting good measurements on this hot, angry Beetle.

 

[Stevehose]

All three were stamped Czech Republic.

I cannot speak to whether two were "counterfeit". But two were stamped 923 and the other (good) one was stamped 723. My current theory is that this stamping is a date code, maybe July was a better batch than September? Don't know. Just happy that we're getting good measurements on this hot, angry Beetle.

923 means the china factory misread the 723 Glad it's working finally.

 

[JFENG]

FWIW, I once bought a German made carb synchronizer from a popular bug place. The website clearly said it was made in Germany. Upon receipt I could tell it was counterfeit and the flow reading it gave was clearly uncalibrated to the units displayed. When I called to complain of false advertising they said, “yes, it’s a copy from China but it is cheaper than the real thing.”

You can blame China but I’ll bet 10:1 it was some enterprising American business person that sent a real one to China, asking, “can you make a fake for 75% less?”

In my personal experience, China copies most often get to market because there is a demonstrated demand from retail sellers for fakes.

John

 

[Arde]

FWIW, I once bought a German made carb synchronizer from a popular bug place. The website clearly said it was made in Germany. Upon receipt I could tell it was counterfeit and the flow reading it gave was clearly uncalibrated to the units displayed. When I called to complain of false advertising they said, “yes, it’s a copy from China but it is cheaper than the real thing.”

You can blame China but I’ll bet 10:1 it was some enterprising American business person that sent a real one to China, asking, “can you make a fake for 75% less?”

In my personal experience, China copies most often get to market because there is a demonstrated demand from retail sellers for fakes.

John

I was offered fake Rolexes and Omegas in Shanghai, no American business person or retailer was involved.
I was offered a foot massage, and a happy ending.
I took none of the above, perhaps that is why I am so unhappy...

 

[JFENG]

I was offered fake Rolexes and Omegas in Shanghai, no American business person or retailer was involved.
I was offered a foot massage, and a happy ending.
I took none of the above, perhaps that is why I am so unhappy...

Just saying it’s not always China which initiates the mfg of this crap. And, if no American tourists bought fake Rolex watches …

 

[lip277]

Just saying it’s not always China which initiates the mfg of this crap. And, if no American tourists bought fake Rolex watches …

LOL
Funny story regarding fake watches.....
I was in the Grand Bazaar in Istanbul several years ago. Was there with some co-workers. (I had been to IST over a dozen times so I was the tour guide - so to speak).
Well, they wanted some 'authentic Turkish bath towles' - and wanted to go to the Grand Bazaar to get them. Sure - why not. I'm always up to poke around in IST.
So - we go in and find a place that has towels that are of interest to them. They enter that stall to do their shopping and such....
I wait outside. My friends are taking their time so I start looking at the booths nearby. One of them is a watch place. Selling knock offs of all your favorite Rolex, Omega and the rest. Some of them really look nice - but I know they are NOT real. TOO inexpensive to be so.
The young fella (maybe about 30 years old) comes out to see me... and try to sell me a watch. I politely decline and in so doing - he sees the watch I have on - a Breitling Aerospace....
He nods his head in approval and says - "We can't copy that one - the digital part is too hard....."
I got a good chuckle out of that.

 

[Arde]

Just saying it’s not always China which initiates the mfg of this crap. And, if no American tourists bought fake Rolex watches …

OK, I tour the labs of a large American Hyperscaler, machines out of a James Bond movie. One of them provides a thermal profile of the die of an integrated circuit, and is used to determine if anything extraneous happened in the supply chain... The thermal profile of one device is anomalous, they decap the part to see what happened. Instead of the original 8 dollar UK part, somebody placed a Chinese knockoff built out of programable logic. No American tourist involved.