VDO style combo gauge questions

Hi,

 I have a newly purchased used Fiberfab widebody speedster. It has VDO tach speedo and combo fuel and oil temp gauge. The oil temp gauge doesn't work at all. It has a sending unit that is tee'd off the oil pressure sender on the left front of the VW engine. Is there anything to look at  first to reasons why the gauge doesn't move at all? Thought I would ask here first before I started replacing the sending unit. My fuel gauge is wonky also. When the tank is full the needle is just a tick above reserve. Thanks in advance.

Original Post

914 or replica 356 gauges?  Photo? Are you sure the second sender is not for dash oil pressure idiot light?  (some solve both with a sender with dual connections.  Remember no teflon tape on senders - they must ground to engine block.  Temp sender is often in one of the oil pressure relief valves or the sump drain - at least they work better there. 

Looks like your multi-gauge is an Asian reproduction.  They are supposed to work with regular VDO senders.

The senders work by providing different resistance to ground, depending on fuel level or temperature, respectively.  

If you go to each sender, remove the wire from it and ground the wire to something either under the hood or on the engine, the respective gauge needle should go from zero (left side) to full scale.  When you remove the wire on the fuel sender or engine sender from ground, the needles should return to zero.  You will not break the gauge by doing this (it's how they are supposed to work) and it will tell you if the gauge is working properly.  I suspect it is, and you have a sender issues as Bill mentioned.

Once you know that, then we can probably help you with the right senders (in a confusing way, of course!)    

The temp range, resistance, on the sender will determine how much and where the needle moves in your Chinese gauge. 

If you look at your sender, there should be some #s engraved along the rim, that will tell you the model number, brand, and temp range.   See picture #1 bellow.  The numbers written in pencil were all taken from the engravings you can see on the sender.  The last line of numbers is the model number... which you can then use to find the " replacement part number on the VDO site. ( I attached at TH bottom of this post.)

 The attached information that may also be useful to you;

· For stock Type 1 VW engine cases/ and 356s, many engine builders are using OEM VW temperature senders because the are short, don't block oil flow, and will not trigger the pressure sender when installed in the same T fitting.

See picture #2 bellow - for reference to notes 1, 2, 3;


1- On the left is the VDO sender 323-427b, 300f, M10 x 1 thread, 22mm, long.


2- In the center is the OEM VW German made sender of the the same M10 x 1 thread, SHORT 10mm, 150c/300F. VW OEM part number #1H0 919 563 - oil temp sender, 0-150c range, used on for a bunch of 70s to late 90s VW cars. Also Audi cars.


They, both ( 1 and 2), have the same 10-180 Ohm range... The OEM VW short one can replace the M10 thread sender for the aftermarket VDO oil temp gauge with 150c/300f range. The short sender will not protrude into the oil passage like the longer VDO unit. The longer VDO unit can trigger the oil pressure sender.


3 - To the right is the more common and cheaper OEM VW sender part #049 919 501 - oil temp sender, short 10mm, 0-120c range also used for mid-70s to mid-90s VW stuff. And commonly used now for small aircooled engines.   I have the VDO version of this one installed in the car, part number 323-088.

4- not pictured, Then there's OEM VW #049 919 563A - oil temp sender, 0-180c range. Same M10 thread and looks just like the sender on the right but used in modern water cooled engines.

Picture #1

IMG_1214

picture #2

image001

Also,  you can find VDO senders at most local Autozones, NAPA, O'Reilleys, etc...  plus Amazon stores... but can also order them on line from many places at discounted prices.

Here is a useful store, witch includes great details- thread, resistance, temp range, and a picture...

-  http://www.egauges.com/VDO-Tem...-Senders-s/35438.htm

https://www.vdo-instruments.co...sensor-only.html?p=1

https://vdo-webshop.nl/en/34-t...ategory=34&n=125

 

Hope this helps...

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Photos (2)

I wish I could see up under the dash. I will need to move a lot of wiring which I will do. I just hate working on under dash issues. Not an easy area for my to get to. The speedo worked for 5 minutes and quit also. Is it usually an issue at the wheel or at the speedo?. I assume the cable isn't being spun or has come undone some how. The car is very very nice with a strong 2276 engine with dual 44 Webers.  Just need to address these detail issues. The car was built and parked with 110 miles on it  in a temp. controlled building in a plastic inflatable cocoon.

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Photos (2)

I pulled the oil temp sender out. Wish I would have taken a picture of it. It is very short with no markings. I placed my voltmeter across it set to resistance. ( not sure the scale)It shows 1.2 ohms resistance cold and drop to zero when I heat it. As it cools the resistance climbs back to 1.2. I assume the thing is working. Not sure why I don't get gauge movement as oil heats. Maybe it is so short it isn't getting to the oil? I will continue to work on this and let you all know.

I've not seen a case tapped like yours. Usually there is a brass T fitting in the side area. The T's generally aren't big enough to hold a temp sender.  The oil pressure sender (black one) looks melted?? Same for the wire where the tape is.  Could the oil pressure sender be blocking flow to temp sender? The wire from front to rear could be bad.  Gauge might not be adequately grounded too.  If you can get to wire on back of temp gauge - you could check it for open front to rear or run wire from sender to gauge outside the vehicle. 

Related image

If your only getting a 1.2 ohms the sender could be bad.,.. most vdo 120c (250C) temperature senders have a resistance of 287ohm to 22.7ohm.... but it's also imortant to check the wiring/ ground on the gauge to eliminate possible sources of problems.

refernece for testing senders.  One of the links I posted earlier had ohm ranges for the senders asreference;

How to Troubleshoot VDO Sending Units- by Quinten Plummer-


VDO produces a third-party line of automotive gauges, ranging from temperature gauges to pressure gauges. VDO sending units monitor your automobile's components and processes and then report this information to your automobile's gauges. If you start to notice odd readings on your gauges, your automobile's components may not be at fault -- there may be a problem with your VDO senders.


1 Test a VDO temperature sender using a multimeter. Switch the multimeter to "Ohms." Touch the temperature sender with the multimeter positive lead, or clamp the positive lead to the sender. Touch or clamp the multimeter black lead to a solid metal portion of your car. The temperature sender ( at room temperature) should register 700 Ohms - 287 Ohm ( spending on sender model) when cold, and 22 Ohms after the car has warmed up.

2 Test the Ohm output of a VDO pressure sender using a multimeter. -- Set the multimeter to "Ohms." Touch or clamp the multimeter black lead to a solid metal portion of the car. Touch the sender with the multimeter positive lead. The sender should register 10 Ohms with the engine off. Start the engine and test the pressure sender again. For engines with 40 psi oil pumps, the sender should register 105 Ohms. It should register 152 Ohms for engines with 60 psi oil pumps.

3 Test your VDO fuel sender with a multimeter. Disconnect the fuel sender positive wire from the fuel gauge; disconnect the negative wire. Touch the negative lead of the multimeter to the negative wire and the positive lead to the positive wire. The fuel sender should show between 10 and 180 Ohms, depending on how much fuel is in the tank. It should register 10 Ohms on a full tank and 180 Ohms on a full tank. If your fuel level falls between full and empty, the Ohm output should register between 10 and 180 Ohms.

 

Also,  it's much easier to work on the gauges if you push them out of their sockets... from behind just push gently... the rubber gasket will release wth the right amount of pushing.  They will dangle from the cables through the hole, but enough for you to see, work and test all connections...

if your car is a VS I can send you their wiring diagram they sent me when they built the car... but always best to make your own, as not all cars are consistent.  The files i have are PDF... I can email, but don't know how to post PDF files on the site.

From VDO tech sheets for testing senders: ( download data sheets from links I posted above)

Sender Testing:

Senders can be tested with an OHM meter that measures from 10 to 2,000 OHMs. Connect the positive lead from the tester to the sender terminal and the negative lead to a good ground. The following readings will occur if the sender is operating properly:

Temperature Sender: Room Temp (Sender Dependent) 300 – 1000 Ohms (•)

Pressure Sender: Engine off (Sender Dependent) 10 Ohms (•), 240 Ohms (•)

I am not sure what scale I had the tester on I will run the test again and get the correct reading. The gauge seems to be wired correctly. If I ground the sender wire the gauge goes full hot as someone earlier suggested checking. So the problem is in the sender itself, lack of good ground or mismatched sender. I will get to the bottom of it and report back.

Yes I love it. It is better than he described. Basically new with a newly built 2276 engine that runs super strong. It has a few things to be sorted but very nice. The price was right as well.  I have driven it over 300 miles in the last week.  I am going to figure out what gearing the trans. axle has I am always wanting to shift to a 5th gear. It cruises at 65mph at 3300rpm. But 65mph doesn't feel like 65 mph. It feels like 45 mph because the car is so solid.  Then engine has a ton of torque so I  might be able to get away with taller gearing. 1st gear is useless and I usually just start in 2nd.  It appears to have had just 110 miles on it when I picked it up. I bought it on the first phone call, he told me that someone was planning on coming to look at it the next day so I pulled the trigger. Glad I did. I hope you like your VS. Is it a the one shown on your avatar?

http://johnmaherracing.com/cal...ar-ratio-calculator/

Put in your rear tire size and 4.125 in the ring & pinion box and if 3300 in 4th is close to 65mph then you know what you have. A 3.88 (later beetle, still around and a popular choice in the Speedster world) would lengthen everything slightly and give nice (and still somewhat legal) cruising speeds. Since you did say "1st gear is useless and I usually just start in 2nd", you might be happier with an aftermarket 3.44 r&p, but 3000- 3500 rpm in 4th is now getting pretty long (what are the police and speeding tickets like where you live?) so plug .93 (later beetle) into 4th to bring those highway speeds a little more in line.

Gene Berg Ent. does do a 5 speed conversion of the type 1 trans-

http://www.geneberg.com/cat.php?cPath=13_387

http://www.geneberg.com/cat.ph...%20Kit&cPath=389

Close ratio gears in a beetle or Speedster with a bigger engine are absolutely fantastic to drive (they change the feel of the car completely), and of all the guys I know personally or online, not 1 who has gone this route would go back to a 4 speed. Yes, it is expensive (count on spending $5,000 or more by the time it's done, with gears and assembly. Superdiff, Quaife or ZF lsd are extra), and it will take a year (you have to send in your parts to be modified and Berg only does them in batches of 10, so "6 weeks" will turn into 6 or 8 months, and then your trans guy has to put it together), but if you endure there's nothing like ripping through the gears and then cruising down the highway in 5th! (think big evil laugh here!).

There are also custom 1st/2nd mainshafts to make 1st gear even longer (got a spare 1,000 or $1100 laying around?), but that's for another day... Al 

PS- I almost forgot (can't believe I did that!)- do you know the engine specs- camshaft? heads? compression? exhaust tubing size? How high does the engine rev with power in 3rd gear?

PS again- Mfactory gear calculator is still not back.

 

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