# Old Tacometer Connect to ECU **URL:** \ **Category:** GENERAL\ **Tags:** how-to\ **Created:** [March 5, 2026, 4:18pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329 "2026-03-05T16:18:53Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [March 5, 2026, 4:18pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/1 "2026-03-05T16:18:53Z")
New here. I am running a EMU Black in a 78 VW Rabbit. I decided to use the original gauge cluster instead of the display unit. The Rabbit came with a tachometer and I have the white wire from the ECU to tap into the tachometer. I was told i will need a type of signal multiplier . Not sure what that is. Any ideas? Thanks. Tony ---
**Author:** ![Knownworldwide](https://avatars.discourse-cdn.com/v4/letter/k/e19adc/32.png) [@Knownworldwide](https://community.ecumaster.com/u/Knownworldwide)\ **Post date:** [March 6, 2026, 6:15am UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/2 "2026-03-06T06:15:40Z")
You can use something like those to generate a traditional square type wave for your existing tachometer to work. [https://www.autometer.com/tach-adapter.html?srsltid=AfmBOopALy3D8kkTtRWpfLpjIszc9iprCLp7nXg5Vn1Ke0jh3Kd-NmrN](https://www.autometer.com/tach-adapter.html?srsltid=AfmBOopALy3D8kkTtRWpfLpjIszc9iprCLp7nXg5Vn1Ke0jh3Kd-NmrN) ---
**Author:** ![SteveDawson](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SteveDawson](https://community.ecumaster.com/u/SteveDawson)\ **Post date:** [March 7, 2026, 4:43pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/3 "2026-03-07T16:43:35Z")
I don’t know what tachometer the Rabbit used, but I can drive the stock VDO tachometer in my 911 directly from the ECU. The same basic tach was used in the 60s, 70s and 80s in various German vehicles. Normal operation is for the ignition system to ground the signal wire (mine is marked TD on the back of the tach). Connecting the tach to one of the ECU digital outputs provides the same functionality. Here’s my configuration: ![image](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/2/24822b8861591ae989bc044479333801a9b31305.png) The multiplier is a 3 because my 6 cylinder engine generates three ignition pulses per revolution. Hope this helps, Steve ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [March 8, 2026, 4:57pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/4 "2026-03-08T16:57:41Z")
Yes it helps. I had a friend help install the ECU and he is not sure how to incorporator the tachometer. It is a VDO and is similar to most German cars from that era. I will give it a try and post some results in the future. Thanks again for the input . ---
**Author:** ![SteveDawson](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SteveDawson](https://community.ecumaster.com/u/SteveDawson)\ **Post date:** [March 8, 2026, 5:35pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/5 "2026-03-08T17:35:16Z")
This is the back of a tachometer like mine. The output from the EMU Black should go to the terminal marked “TD”. ![image](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/9/96c6583a08b495686112a9828de6685c503539cb.jpeg) ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [March 9, 2026, 3:06pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/6 "2026-03-09T15:06:04Z")
Hi Steve. So you are saying that I can take the signal from the ECU Black after making adjustments to the ECU outputs for the tach, I’m using. I then do not need to buy a Autometer adapter? And where are you located? Thanks. Tony ---
**Author:** ![Knownworldwide](https://avatars.discourse-cdn.com/v4/letter/k/e19adc/32.png) [@Knownworldwide](https://community.ecumaster.com/u/Knownworldwide)\ **Post date:** [March 13, 2026, 5:14am UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/7 "2026-03-13T05:14:48Z")
so does your tachometer work or not at all? what year 911? ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [March 13, 2026, 4:10pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/8 "2026-03-13T16:10:26Z")
![Rabbit Tach](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/b/b71a151bf8dc21441cde7ae0545d8d241a7cda89.jpeg)I have the Tachometer from a 78 VW Rabbit. It works. It looks like i will have to purchase a RPM adapter to make it work. Thanks. Tony ---
**Author:** ![Knownworldwide](https://avatars.discourse-cdn.com/v4/letter/k/e19adc/32.png) [@Knownworldwide](https://community.ecumaster.com/u/Knownworldwide)\ **Post date:** [March 13, 2026, 5:27pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/9 "2026-03-13T17:27:34Z")
Sorry I meant to as Steve what year 911 he had and if his rabbit tach is working or not. As you have said, most of these things need tach adaptor. The 911 maybe newer and they can use a different computer system to drive it. ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [March 13, 2026, 6:07pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/10 "2026-03-13T18:07:01Z")
No problem I will post a update when I install the RPM Adapter. Tony ---
**Author:** ![ProperTuningOG](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/propertuningog/32/3481_2.png) [@ProperTuningOG](https://community.ecumaster.com/u/ProperTuningOG)\ **Post date:** [March 13, 2026, 6:47pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/11 "2026-03-13T18:47:59Z")
Why not just try a pullup resistor. 1k to 12v. You will be converting the 0v signal to 12v signal. ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [March 13, 2026, 8:54pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/12 "2026-03-13T20:54:13Z")
That sounds simple but not sure how to. Would need a sketch showing how to connect. ---
**Author:** ![ProperTuningOG](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/propertuningog/32/3481_2.png) [@ProperTuningOG](https://community.ecumaster.com/u/ProperTuningOG)\ **Post date:** [March 13, 2026, 9:10pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/13 "2026-03-13T21:10:46Z")
Wire normal then use a 1k resistor from the signal to 12v. ![image](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/8/810977ebd522fb8ea4b349be6ccbddb974baac72.png) ---
**Author:** ![FloorItGarage](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/flooritgarage/32/61_2.png) [@FloorItGarage](https://community.ecumaster.com/u/FloorItGarage)\ **Post date:** [March 14, 2026, 3:06am UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/14 "2026-03-14T03:06:25Z")
![image](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/d/debfff1a4811983593659c85d045f62097fab0e4.png) It should have this internally already, enabled when aux 4 is used as the tach output. I’ve found with older tachometers that are designed to pickup off the coil negative, Black and Classic need an adapter. I haven’t measured it personally but supposedly the negative of the coil field collapsing can push voltages well beyond 12 or 14v (I’ve read 60, not sure about that tho), some tach’s (Toyota’s for example) there’s an inline resistor you can bypass and then Aux 4 does the job. ---
**Author:** ![ProperTuningOG](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/propertuningog/32/3481_2.png) [@ProperTuningOG](https://community.ecumaster.com/u/ProperTuningOG)\ **Post date:** [March 14, 2026, 3:58pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/15 "2026-03-14T15:58:36Z")
Then he could pull to ground. Just try to get the signal in the right condition. ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [April 13, 2026, 4:47pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/16 "2026-04-13T16:47:39Z")
I finally got around to installing a Widgit Man controller to my 78 Rabbit. I connected the white output wire from the ECU to the signal in in the Widgit. Not working at the moment. Do I need to make a change in the ECU? This is new to me so it’s a challenge, Thanks Tony ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [April 18, 2026, 2:22pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/17 "2026-04-18T14:22:55Z")
![Oscope](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/a/a6c44c4a889ddbe9ff8ee69b2ef6f9d9b2a76ae7.jpeg)With a friend who has a small oscope, he was able to get the signal from the Black ECU. The signal fropm the Widget Man converter was a broken square wave and then it would go flat to around 12v. Should the signal from the converter be a claen square wave similar to the wave from the ECU? THanks ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [April 18, 2026, 2:23pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/18 "2026-04-18T14:23:41Z")
![Widget man](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/1/1a1344c8de4a80bf3b79a28c9508960c585a4609.jpeg)Here is the converter. ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [April 18, 2026, 2:51pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/19 "2026-04-18T14:51:05Z")
![After Relay](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/9/912ed177ded754b95826f7d3b2326b7be9c117e3.jpeg) This is the signal after the controller. Not sure what I’m seeing here. Doesn’t look right. Any thoughts? Tony ---
**Author:** ![tonysblackecu](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@tonysblackecu](https://community.ecumaster.com/u/tonysblackecu)\ **Post date:** [April 18, 2026, 2:54pm UTC](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329/20 "2026-04-18T14:54:09Z")
Looking for a 1K resistor to try. Thanks [Next page](https://community.ecumaster.com/t/old-tacometer-connect-to-ecu/5329.md?page=2)