lost tach

[Junkman]

I just replaced my 85SD dash with a beautiful crack free from a 89 gasser. Everything works except the tach which worked before I took the dash out. I'm thinking that I missed plugging a wire somewhere.

The plugs at the tach are connected correctly as there is only 1 way to connect them. Is there another connection between the tach & the sender?

I have a 2 wire (black) junction block that is loose left of the center vent but I haven't found anything that fits.

[gmcop1]

You may have fried the OVP. See if the A/C compressor kicks in when you set it for full A/C. If the tach and the compressor both cease working it is the OVP. It can be bad even if the fuse looks good.
Gary C
85 300D, 87 SDL

[funola]

Originally Posted by Junkman

I just replaced my 85SD dash with a beautiful crack free from a 89 gasser. Everything works except the tach which worked before I took the dash out. I'm thinking that I missed plugging a wire somewhere.

The plugs at the tach are connected correctly as there is only 1 way to connect them. Is there another connection between the tach & the sender?

I have a 2 wire (black) junction block that is loose left of the center vent but I haven't found anything that fits.

Maybe a Mercedes gasser tach is different. But most gasser tachs run off the distributor coil pulses, which is very different than our diesel tachs, which runs off a mag pickup on the harmonic balancer. That may explain why your gasser tach is not working.