VDO EGT problems

[Greasecar]

I ordered a VDO Cockpit sieries EGT gauge kit from New South Performance, installed it but it does not seem to be working. Unfortunately, NewSouth does not offer a customer support contact number or email and it looks as though their products are drop shipped from various distributors around the country so I don't know who to ask.

I am using an ALH exhaust manifold and installed the thermocouple in a plate bolted onto the old EGR tube port.  The probe projects right into the exhaust stream, the wires are connected as instructed but the gauge will only read between 250F and 350F (250 is where the gauge starts).  This is even at WOT 90mph on the highway running 17-18 PSI boost

I used my multimeter and there is a strong 12V signal going into the gauge and a good ground.  I even jumped the ground to the battery and it made no difference.  The red and yellow thermocouple wires have good connection at the thermocouple screw terminals and at the gauge and were not trimmed at all.  According to the thermocouple diagram the red lead is supposed to be positive and yellow negative and I assume the thermo couple creates a resistance signal that the gauge reads.  According to my multi meter, the gauge does not seem to be providing 12v to the thermocouple.

I guess my questions are:
-Has anyone had issues with these gauges?
-Is my diagnostic procedure correct?
-Is it possible the gauge is working and my max EGT is actually 350F?

Any input will be greatly appriciated.

[giulianot]

With my experience, when using type k thermocouple wire the yellow is the positive lead and the red is the negative lead,  when the thermocouple probe is heated a millivoltage is produced. ie more temp higher mV lower temp less mV.

[rallydiesel]

I have heard the VDO thermocouples not being that great. I would say return it and get an Aircraft Spruce probe and an Isspro gauge. I just installed this combo and it has very fast response.

[Greasecar]

In terms of the yeloww/red= pos/neg, I was writing from memory but the wiring was done to the VDO schematic.  So if my unerstanding is correct the way it should work is that the gauge gives DC V down one lead and the probe regulates that voltge and sends a temp corresponding voltage signal up the other lead.  Any idea on how many milivolts = # degrees?


I was thinking about getting a probe from Spruce (only $23), anyone know if it is compatible with the VDO?

I'm also wondering if perhaps my probe just isn't in the right spot.  After a drive I took today the gighest I registered was 400. I took another peek under the hood and the EGR flange does sit an inch or more proud of the runners, but if so, I am suprised there would be a 1000 F or so temp discrepency.

What sort of temps are people seeing in average driving conditions?  This is my first time running with an EGT meter but I was expecting temps +/- 1000 F.

[Black Smokin' Diesel]

For best results the probe should be in the direct path of the exhaust gasses.

Any K-type probe is compatible with any K-type gauge and wiring and vice-versa.

[Greasecar]

Andrew-

The VDO unit has a power and ground for the light then 4 terminals on the gauge body: 12v, ground, yellow and red (yellow and ted are the +/- of the thermocouple leads).

Good idea on pulling the probe and throwing it in the path of a tourch at least that will verify as to whether it is working or not.  It sounds like my main issue may just be where I have it installed.

[Riverfurm]

I have the same setup and mine works great. I have the probe in the ex. manifold right in the center where all the runners cobine. Works fast when I floor it and have some black smoke coming out.

[Vincent Waldon]

The signal coming off the red and yellow leads of a K thermocouple is millivolts at best... very difficult to read without a sensitive multimeter.  You won't see 12V on either of those wires.

I second the advice of someone else.. pull the probe and see if it responds to a propane torch flame... Google should be able to tell you how hot that is.

[Greasecar]

RiverFurm-
What sort of temps have you been seeing on your car?

I saw Jake's thread on the Spruce thermocouple and it looks like he tapped his in the same spot.  I was trying to take the easy way out without having to pull the manifold.

[saurkraut]

The threads for the the adaptor for the Spruce thermocouple and VDO thermocouple are the same.  1/8'" pipe thread, I think.

Here's a Spruce thermocouple my 1.5TD set up:




Crap, how do you get a pic to show up on this board?

Link: http://i192.photobucket.com/albums/z236/dieselkraftstoff/SSPX0007.jpg?t=1194271543

[Mk2Fanatic]

delete this part  "?t=1194271543"  anything after the pic extension will not allow it to show up.

[saurkraut]

K

Thanks!

[Greasecar]

My problem has got to be the position of the thermocouple.  I pulled the probe, put a torch to it and was able to get a reading up near 1000F.  The sensitivity is probably not the best but it is working.  I was required to turn the ignition on to get a reading (must be the signal amplifier).

Due to the way I installed the probe I was able to adjuct it in order to get a bit more penetration which also lead to an exhaust leak at the sensor flange.  The combination of the deeper penetration and exhaust leak (causing more exhaust to travel past the thermocouple) did gause a rise in measured EGT.  Looks like I'll have to pull the turbo and manifold to drill and tap a new hole.  I'm using an integrated TDI turbo/manifold which does not make for easy and safe drilling and tapping.  I had also thought about pulling the head pipe and welding a bung to that which may be easier though the EGTs will register a bit lower.

The VDO sender adaptor is 1/4 or 3/8 NPT.

[saurkraut]

Don't to a post turbo measurement.

You get a temperature reading, but its virtually useless.