VDO Series one speedometer

Texasdoc · #1 (**permalink**) 12-01-2018, 02:57 PM

Does anyone have a VDO speedometer that they are willing to part with that I can use for parts? My Series 1 speedometer is freaking out and I need to see if I can fix it.

For the most part, it works ok. While decelerating, at almost a stop, the speed indicator needle hovers at 20 mph even as I continue to slow down. Then, as soon as I stop, the needle drops suddenly to zero. This happens almost every time. Then after driving for about 20 minutes, the whole gauge starts to freak out. The mileage LCD readout digits start blinking irregular characters (not even numbers or letters) and the speed indicator jumps to a random location. I was sitting at a stop light and looked down - it was pegged around 160! I reached behind the gauge and unplugged the power but the needle stayed there until the next restart.

It isn't the sender, the tko600 stock sender seems to be working fine, plus it did the slow down bouncy thing when I had the T5 with the mechanical send in the car. I replaced the sender to gauge wires as well.

I opened the gauge and looked around the circuit board but didn't see any obvious blown capacitors or resistors. I didn't see any cold solder joints.

None of the other gauges are acting up and the power is steady. They all share a common power source and ground.

Karl Bebout · #2 (**permalink**) 12-01-2018, 05:54 PM

Check with Speedhut. They make excellent meters, have excellent customer service, have a nice discount special going on for the holidays. They can match the size, face, pointers, and font from just about all makes.

Worth taking a look. My 2¢ worth.

Texasdoc · #3 (**permalink**) 12-01-2018, 06:32 PM

If I change out the gauge, the odometer will be wrong then I'll have to deal with that paperwork if I ever sell. Hoping to fix this one. If not I can get a new one.

Karl Bebout · #4 (**permalink**) 12-01-2018, 06:44 PM

AuContraire Doc, Depending on which Speedhut speedo, they can either set the odometer at what mileage you want it to show or you can set the GPS driven speedo to show what you want with a sequence of button pushing.

spdbrake · #5 (**permalink**) 12-01-2018, 07:04 PM

I had a similar issue on my VDO's odometer flaking out at low speed and at idle. Turned out to be a loose connection at the inductive pickup on the diff. (mine does not use a trans sender)
http://www.vdo-gauges.com/media/inst...ter%28c%29.pdf

If your sender is attached to the Trans gear its a Hall Effect unit and that IS a failure symptom of those.

There is a shop in Austin that can repair your Speedo if you don't have that issue.
Overseas Speedometer | Speedometer & Odometer Repairs

Ron61 · #6 (**permalink**) 12-02-2018, 03:30 AM

I had a similar problem with the one in my Cobra and the hall effect unit was good so I started tracing the leads. Turned out that the sending lead had a broken place in the insulation and that was touching a place that caused it. I just replaced the leads and never had another problem.

Ron

scott cooper · #7 (**permalink**) 12-02-2018, 05:37 AM

I had the exact issue, turned out to be a loose connection on the back of the unit, cleaned and tightened been working perfect

66AC · #8 (**permalink**) 12-02-2018, 08:44 AM

I would suggest you check your wiring first. Then if it all checks out you may want to call Bob's Speedometer Repair. He has done some great work for me on repair and also restoration of various gauges....

Here is his link...

https://www.bobsspeedometer.com/1/120/index.asp

Texasdoc · #9 (**permalink**) 12-02-2018, 06:14 PM

I'll check the wiring again but already did that. I don't know how the tko speed sensor works (Hall vs magnetic vs voltage) or how to check the sender itself. I will just have to check the wiring and connectors. Right now I have a shielded wire from the gauge to the trans, two signal wires to the sender and the shielding grounded at the gauge end. I'll check it all again.

Is the sender on the tko replaceable? I can see replacement connectors but not sensors. Thanks again.

spdbrake · #10 (**permalink**) 12-03-2018, 07:02 AM

If you have a TKO, TR3550,T56,T5 Ford sender it should look like this
https://www.summitracing.com/tx/part...0013/overview/

Speedo Sensor, 3 wire Digital, Ford gear drive with 10' Pigtail harness

They are made in a 90 deg offset for clearance as well.

Best if you can get a PN off yours to see if its a 16 PPR (pulse per rev) or an 8 PPR unit.

16 PPR is more common.

Texasdoc · #11 (**permalink**) 12-03-2018, 06:44 PM

Quote:

Originally Posted by spdbrake

If you have a TKO, TR3550,T56,T5 Ford sender it should look like this
https://www.summitracing.com/tx/part...0013/overview/

Speedo Sensor, 3 wire Digital, Ford gear drive with 10' Pigtail harness
.

That looks like the mechanical speed sensor I had on the T5. The TKO has an electronic sensor that only has two wires coming out of it. I think it is an inductive pickup (whatever that means). I'll get some new shielded wire and re-run the wire from the transmission to the gauge. I will also put it on its own power feed and ground circuit to avoid contamination from the other gauges.

I'll eventually return and report when I get it done. I may have just run out of driving season this year. It's supposed to be 29 tomorrow morning. It was almost 80 on Saturday.

spdbrake · #12 (**permalink**) 12-03-2018, 07:17 PM

Yes I see that in the repair manual. I've only seen those on OEM installations. They are pretty bullet proof. No moving parts its just a mag pickup. If you remove it and it rattles its toast though.

Supposed to be 31 here tonight (just south of Ft. Worth)

Schmidtal · #13 (**permalink**) 12-06-2018, 02:05 PM

I needed a VDO oil temp gauge and talked to the mfg. They were good to work with, you might call them and ask about your problem.