perma tune cd box
 

I am in the process of buying a perma tune 911 model CD unit for my 1983 911SC. Pelican parts sells the unit for $ 535.00 it has the six pin connection at the bottom of the box. Other parts retailers sell the perma tune box for $ 435.00 --$ 455.00 with a pigtail six pin connection coming from the box . The Pelican box pictured in their catalog is silver. The other boxes are black. My questions are 1. Do the differences in the type of connection , and in the color of the boxes make one better than the other ? 2 Almost every article I've read states that the first suspect of ignition problems is the ignition coil the second is the CD unit . Coil failure can cause CD failure . Is this true? 3 If OEM unit doesn't make humming it has failed ?

Here is what Permatune shows for the SC:
http://permatune.com/images/newmods/911SCsmall.jpg

Unless you have a really old permatune box, the new ones don't make any noise.

perma tune
 

Thanks for your input Kurt V . That's the unit I mentioned in my thread . The one advertised by Pelican Parts is not like the one pictured in your response . That's why I wondered if there was any difference other than the price . I'm replacing the original unit which is supposed to make a humming noise when it's working .

Eliozar,

If your Bosch CDI unit is not whining or humming ... it might be bad, but all electrical connectors should be cleaned thoroughly and have the sides of the female 'Faston' connectors retensioned to assure good, tight connections.

My usual choice for cleaning the connectors includes 91% isopropyl alcohol, 9% pickling vinegar, oxalic acid cleanser, or liquid silver cleaner for silverware/flatware .... and a supply of pipe cleaners, Q-tips, cotton square pads, etc. A thorough rinse with distilled water and blow dry with compressed air usually completes the process.

After cleaning, be sure to verify the presence of +12 Volt power at terminal #15 of the CDI 6-pin plug.

Dow Corning 4 Silicone Grease applied sparingly is insurance against assault from moisture and oxygen.

Plug in the harness connector and check to see if the CDI hums or whines as normal? If so, try to start engine.

http://forums.pelicanparts.com/porsche-911-technical-forum/158541-ignition-troubleshooting.html

http://forums.pelicanparts.com/showthread.php?s=&threadid=203100&highlight=6pin+c di

Thanks for the information Early-S-Man . I removed the unit from the car and opened it up . The wires connected to transisters looked burned and the covering on them felt waxy where it had melted from the heat or maybe a short in the coil . I bought a new perma tune yesterday . I'll install it today. I'll let you know how things turned out. Nice to hear from a fellow San Angeloan .