Gasser tach conversion prep

[ktzdsl]

Not newbie; just dumMe!
About  to construct a hybrid instrument cluster for my 82 caddy. I have a 1984 GTI
cluster and the 82 cluster. My speedometer being used because it has correct mileage and recently repaired and calibrated. Removed the clock from 82 cluster; swapped LEDs from 82 to the case for the 84 GTI(for glow plug led), installed the gas tach in place of the clock. Connected separate wire to the sender post. Was almost completed with the job, when I noticed that the plastic circuit was beginning to separate at the top,about 1 1/2 inches, right by the main connector.

Here are the questions I have:

Q1. Can the filament be re-glued?
Q2. Should it be re-glued?
Q3. What type of glue or should I use transparent tape?

I took my caddy to a alternator/generator repair shop and had them test the W-terminal. Got 7-8 volts with engine idling.

Q4. Is it a valid test of the tachometer to connect the W-terminal to the gas tach and watch for about 4000 RPM at idle?
Q5. What other type of test can be/should be made?

Thanks all.
ken

[fatmobile]

Doesn't hurt for the plastic to seperate,..
 as long as the copper traces don't break.

 You changed some resistors and caps in the tach before you installed it right? Otherwise it will just peg.

[ktzdsl]

Noticed that when I re-installed the cluster, that I lost some indicator lights and function. Directional light works, alternator light works, but bright light indicator and wand would not function. I will keep looking. Also did not direct connect the tach to the W terminal, only touched the wires with engine running. First tach I tried only registered 200 rpm. The second one did a "peak", so I know it is good. Think I should use the 200 rpm tach for the modification?  

Nothing has been modified on the GTI tach. I am totally dense when it comes to electrical testing etc, so installed the GTI tach to be able to test the only way I could think of testing, connect and see whether the tach needle responded. I read somewhere that it normally reads about 4000 rpm (peaks out?) before any modifications.
I have also read some 2005 and 2006 entries and am now beginning to get clarification on specifications for the resistors and capacitors required for the modification. Like whether the devices have to be polarized or non-polarized, whether capacitors have to be electrolytic or non-electrolytic and the voltage of the resistors and capacitors. Plus learning to understand the symbols; i.e., nF = nanoFarads, uF = microFarads. Only thing left to do, besides purchase the components, is to determine how to safely remove and replace the tach needle, determine what type of solder to purchase, what type of soldering heat range is required, what type and size of wire is required and if I cannot find an expert circuit board technician, practice on something to build up my own confidence and expertise.
Thanks.
ken