Millennium Falcon
Veteran Member
I thought this info would fall under the "google it" catagory since it seems so basic.... I i didnt want to ask a question that has been asked a million times so I tried searching it and didnt come up with much. So here are my findings. I realize its elementary but maybe it will help someone.
Ive been using a tiny tach on my ALH swap but really wanted an analog tach. So I looked at my pinout and found that #27 pin of a 120 pin alh ECU is the tach signal. The book says Green/brown wire) It looks like the AHU, and 80 pin ALH have a wire in the harness for tach signal but the 120 pin ALH does not.
The 3rd hole in from the left in the row above the blue wire is #27. This is the larger of the two ECU plugs.
When I disassembled the plug I found the pin to be in place with a small piece of insulation (brown & Green) not sure if this is how all ALH's are or if someone cut mine... I have two harnesses and they both are like this.
Knife is pointing at #27
Here is the pin removed.
I stole a pin and a length of wire from a spare harness......
I put everything back together and hooked it up to the tach. This one has adjustable dip switches but I didnt have to mess with them at all. It was dead on right out of the box.
I compared the new tach with my old tach and VCDS. All is good! Dont worry this engine is in my 71 year old Jeep and will never see 4000 rpm. I chose this tach because its very easy to read from 1500-2550 which is where i usually live.
The final product!
https://youtu.be/9jLoXL-lgGA
Hopefully this can assist someone who is trying to get info on this procedure. Thanks!
Ive been using a tiny tach on my ALH swap but really wanted an analog tach. So I looked at my pinout and found that #27 pin of a 120 pin alh ECU is the tach signal. The book says Green/brown wire) It looks like the AHU, and 80 pin ALH have a wire in the harness for tach signal but the 120 pin ALH does not.
The 3rd hole in from the left in the row above the blue wire is #27. This is the larger of the two ECU plugs.
When I disassembled the plug I found the pin to be in place with a small piece of insulation (brown & Green) not sure if this is how all ALH's are or if someone cut mine... I have two harnesses and they both are like this.
Knife is pointing at #27
Here is the pin removed.
I stole a pin and a length of wire from a spare harness......
I put everything back together and hooked it up to the tach. This one has adjustable dip switches but I didnt have to mess with them at all. It was dead on right out of the box.
I compared the new tach with my old tach and VCDS. All is good! Dont worry this engine is in my 71 year old Jeep and will never see 4000 rpm. I chose this tach because its very easy to read from 1500-2550 which is where i usually live.
The final product!
https://youtu.be/9jLoXL-lgGA
Hopefully this can assist someone who is trying to get info on this procedure. Thanks!
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