Cluster Conversion

[myersdp85]

Hey guys. First off im new to the site. I have a project going on right now with my 1985 k10 chevy 1/2 ton. Im working on putting a factory tach from a 77 blazer cluster into my 85 cluster where the fuel gauge sits and moving the fuel gauge to an empty slot on the left part of the cluster. I had a super tach two mounted on the column and it worked just fine. the new tach i just put in when i start the truck pins out at max. what can i do.

I also have problems with the new fuel gauge. I first wired it with test leads and it reads just fine. i have two fuel tanks and their both full. However with my new wiring harness i made for it it doesn't read the way it does with test leads. They are wired the same. what do i need to do from here.

[bake74]

     1st off welcome to the site from California.  Next we will need more information on your "wiring harness" you made.  Go to the tech section here and search wiring diagram and pick your truck and look at the wiring diagram and see if it matches what you did.
     The pegging of the tach to max sounds like a short or wire got crossed.  The new fuel gage, is it for the right year of truck for the printed circuit board ?  Or, I am assuming it is a stock one and not a digital one.  More information will help everyone out in helping you.
     Merry Christmas and welcome to the site.     

[myersdp85]

Well there is nothing special about my wiring harness. I just made electrical connections from where my original fuel gauge sat and moved them to where the fourth gauge location is on the lower left portion of the cluster. I made sure that my connections for ground power and sending unit were correct. What ive done is pulled the fuel gauge and tach from a 77 blazer cluster to put into my 85 k10 cluster so that i have an original tach and fuel gauge for my truck. Those are the only two parts im using from the other cluster. Everything else is from my original cluster. Im not using digitals im using stock gauges.

I have been working on it over the last week and i believe that my tach is needing a rebuild and my fuel gauge needs to be calibrated for my 85 sending unit.

What else can i clear up for you guys.

[Captkaos]

Fuel gauge from any year will work with any year sending unit.  If it is reading wrong search the tech section for the fuel gauge info.

If you moved stuff around, you may be missing stuff in the printed circuit.  it has to be a tach circuit for everything to work correctly (have the correct lead going to the gauges.

[birddog615]

I have a factory tach in my '79 and it pegs out when the truck is idling also. If I idle the truck way down the tach will drop some, so it seems like a resistor is bad or something... I don't know. From what I've researched, this is a common issue due to the circuit board on the back of the tach. There are two places I've found that repair them: http://www.tachman.com/index.htm and http://autoinstrumentrepair.com/. Hope this helps!

[Captkaos]

birddog615, yours is bad and definitely needs repairing.  I can recommend tachman.

BTW 77- down clusters are not a bolt in for 78 and ups...