944 Tachometer connector decoding.
01-29-2018, 01:55 AM
#1
1st Gear
Thread Starter
Join Date: Jan 2018
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
944 Tachometer connector decoding.
I have a 10/82 dated 944 tachometer/economy gauge with eight spade style pins on the rear and I'm trying to figure out the correct wiring procedure for proper function. My research has mostly turned up either a six pin tachometer instruction(meaning four numbered pins and two H designated pins) or a very in depth eight pin breakdown that to me is a bit finicky to understand. The detailed breakdown I found is as follows..
Tachs Pins:
1- {Black/Yellow Engine} Speed (ignition) switched +12V
2- {Green or Green/Yellow} Injection Signal (wave) (internal connection to HG)
3- {Gray/Blue} Speedo Hall sensor (wave signal)
4- {Blue/Yellow} Ground , Coolant Temp gauge is feed from this pin
5- {Black Switched} +12V (is internal connection to H+)
6- {Green} Ignition pulse (neg side of coil and typically Green DME Wire #1
Speedometer Connections to Tach:
HG {Green/Red} Hall sensor Pulse (Square wave 1-6 Volts generated by Hall effect on Front left wheel spinning)
H+ {Black Switched} 12V supplied jump on pin 5 and internal VDO connection to H+
I'm going to admit I'm not the best when it comes to wiring but I can usually read a wiring diagram and understand it. However some of these lead me to believe one or more pins can serve the same function. Going based off of the above description my best guess would be coil to pin six, ground to pin four and hot to either pin five, pin one or pin H+. Now I'm not a fan of the "I think that's the right way" routine of fixing things and I would prefer to know the exact pins to avoid further confusion and troubleshooting. I called a dealership in hopes to get an old timer or a connector diagram to help me out but the technician literally told me the ECU could be bad and to bring the car in so that didn't help at all.. I was hoping anyone with more Porsche expertise or better yet an actual automotive electrician would throw their opinions up here and give me a better idea. Any help or recomendations would be greatly appreciated and any further information can be proided upon request.
Thank you.
Tachs Pins:
1- {Black/Yellow Engine} Speed (ignition) switched +12V
2- {Green or Green/Yellow} Injection Signal (wave) (internal connection to HG)
3- {Gray/Blue} Speedo Hall sensor (wave signal)
4- {Blue/Yellow} Ground , Coolant Temp gauge is feed from this pin
5- {Black Switched} +12V (is internal connection to H+)
6- {Green} Ignition pulse (neg side of coil and typically Green DME Wire #1
Speedometer Connections to Tach:
HG {Green/Red} Hall sensor Pulse (Square wave 1-6 Volts generated by Hall effect on Front left wheel spinning)
H+ {Black Switched} 12V supplied jump on pin 5 and internal VDO connection to H+
I'm going to admit I'm not the best when it comes to wiring but I can usually read a wiring diagram and understand it. However some of these lead me to believe one or more pins can serve the same function. Going based off of the above description my best guess would be coil to pin six, ground to pin four and hot to either pin five, pin one or pin H+. Now I'm not a fan of the "I think that's the right way" routine of fixing things and I would prefer to know the exact pins to avoid further confusion and troubleshooting. I called a dealership in hopes to get an old timer or a connector diagram to help me out but the technician literally told me the ECU could be bad and to bring the car in so that didn't help at all.. I was hoping anyone with more Porsche expertise or better yet an actual automotive electrician would throw their opinions up here and give me a better idea. Any help or recomendations would be greatly appreciated and any further information can be proided upon request.
Thank you.
01-29-2018, 11:29 AM
#2
Check this out: https://www.pelicanparts.com/944/ele...l_diagrams.htm
This one specifically contains the tach, with the 8 pin connections: https://www.pelicanparts.com/944/ele...944_84_4_2.jpg
I used these recently to get my tach wired, but I was hooking up an early style tach to an S engine, so I did a bit of improvising. I'm not great with electrical diagrams, but if you take the time to sit down and trace where everything goes (the diagrams are all chopped up, you'll need to print them out and tape them together), you should be able to work out where all the wires come from. Alternatively, find someone better at wiring diagams than you and have them help you interpret the diagram.
This one specifically contains the tach, with the 8 pin connections: https://www.pelicanparts.com/944/ele...944_84_4_2.jpg
I used these recently to get my tach wired, but I was hooking up an early style tach to an S engine, so I did a bit of improvising. I'm not great with electrical diagrams, but if you take the time to sit down and trace where everything goes (the diagrams are all chopped up, you'll need to print them out and tape them together), you should be able to work out where all the wires come from. Alternatively, find someone better at wiring diagams than you and have them help you interpret the diagram.