I replaced my heater core last weekend. I had my friend start the car and I watched for leakage, etc.... Well, he makes the comment, Do you usually have a tach??? I replied, yes, well, the tach is dead. It doesnt move at all. The only thing I can figure is that I might have knocked something loose while working under the hood getting the hoses off of the heater core....... What does the tach run off of. I didnt see anything out of place..... Where should I start??? It is totally dead, nothing, it has never done this before. And, yes, it was working before I started the project....

Help me out here

 

I don't have an answer for ya, but I have a similar problem. My tach ('90 IROC) reads extraordinarily high. It started this after some work I did on intake manifold (new gaskets,etc.). I actually think it may have something to do with disconnecting/connecting the battery. Did you disconnect the battery when you put new radiator in? I can't seem to chase the electrons in the skematics to determine tach inputs. Let me know if you figure this out.

 

The tach wire wich is white, I believe, needs to be hooked to the negative side of the ignition coil {signal wire that goes to the distributer}. Hope that solves your prob.

Jay

 

SAME THING HAPPENED TO ME. After about 3 days of it not working, it finally corrected itself and began working. I don't know what it's problem was, but it fixed itself.

Only thing u can do is look on the side of the coil wire to see if u bumped ur tach wire and knocked it off. If not then give it a few days.

Sean

 

I'll check my wiring again, but this the stock wiring stuff that comes with the TPI and it is fairly murphy proof being modular and all. Distributor has a two-wire bundle that leads to the external coil

 

My tach dont work until I get to 50 mph or If I gas it down it will kick in and start working. But until I get it kicked in the engine misses, but when I get it working the engine runs smooth and good. When I shut the car off the tach just pegs itself.

 

Sorry it took me so long to get back. I checked the wire on the coil and it seems to be fine. The tach actually worked a little the other day, it wasnt working right, it was jumping all over, but it did show some life. Any more options??

 

I dunno if mine is different cuz its a 4 barrel, but my tach is connected to the back of the distributor. take a look at the connector maybe? its not too hard to find.

 

The tach worked great yesterday. Now it is dead again today. I dont know why it is acting so erratic???