chuck Basics

Hello,
I recently bought a 1978 Porsche 928. This was imported from Germany to New Mexico many years ago and has never seen snow and was never left outside. It has been in storage for 10 years plus It is ultra clean and clean rust free underneath. BUT it has a few electrical problems I need help with. First I would like to replace all the dash panel incandescent bulbs behind the panel (19 small ones?) with LED bulbs. Also the 3 larger ones. Anyone have a place and part # that will work?? Also, so far, the speedometer and odometer do not work. The gears on the odometer are all good but I may replace the large 1st gear anyhow since people seem to have a problem with it deteriorating. There are 2? electrolytic caps on the speedo pc board and one is shorted and blown. I think it's a 100 mfd/16v. And a resistor wired to the pos of this cap is badly burned but does check 33 ohm out of circuit. Color code is burnt off. I need to know what this resistor is and I could really use a scrematic for the speedometer board. Any help will be greatly appreciated. Thank you Porsche owners.

Mrmerlin

Welcome with your new project,
please post pictures of the electrical damage

jpitman2

Welcome to the tank! Apart from what you have posted, everything else works? You have done very well indeed! Speedo is driven by pulses from a reed relay on the back cover of the diff, but the usual problem is poor contact at a connection in the front of the spare wheel well, under a plastic cover - disconnect, apply Deoxit, reconnect, try again. While you are in that area check out the battery (under the spare), its posts and ground cable. In all electrical problems Deoxit is your friend. MANY electrical problems come back to failed relays, especially fuel pump, which is a special , although readily available. Other common problem is botches perpetrated by previous owners/mechanics trying to save $, not knowing what they are doing. Get a set of manuals - soft form is available from Jim Morehouse, who sells through our vendors like 928srus (Roger T).
Remove the CEB cover (pax footwell) and check the fuses, look for signs of excess heat anywhere, remove and clean fuse ends, clean and Deoxit the contacts.
jp 83 Euro S AT 57k

Wisconsin Joe

Welcome.

The list of issues from Jpitman is common, but I think you identified a couple of bad capacitors on the board. This happens, although not as often.

There have been threads on the repair, I can't remember or find them right now.

Same with LEDs. Some folks have replaced them.

Some diligent searching may generate results. Or someone smarter than me may be able to point you in the right direction.

And, as is tradition on here...

THIS...

rjtw

Welcome!!

I just replaced all the bulbs on mine, but with incandescents. Here’s the process of pod removal, with some handy links: https://rennlist.com/forums/928-foru...l#post16362998

On the speedo, three words: Palo Alto Speedometer. I just had the work on mine when I had the pod out, and they know their 928s. They replaced two caps on mine (preventative), replaced the broken odo gear, and calibrated it. Works great.

Finally you will need to familiarize yourself with our famous instrument flexible PCB aka foil. See post 150 in the above thread for links to Dwayne’s great refurb threads and inspect yours as appropriate.

Oh, Roger (ROG100) sells an update kit that replaces all the bulbs with LEDs AND uses hard PCBs, getting rid of the old foil. That might be perfect for you.

THREAD...

Rick

jpitman2

.....Is Useless without.....
jp 83 Euro S AT 57k

chuck Basics

There is not much to post and will not help I think.. A burned resistor is a burned resistor. It also burned the circuit board black under the resistor. And a shorted capacitor just swells up and pushes out the rubber plug on the bottom and checks shorted. All I need is what I asked for. Thanks.

Mrmerlin

..

Mrmerlin

Ahhh OK,..
since I can not see what your working on,
and the parts you have ,
you are the smartest one in the room,
good luck

chuck Basics

Thanks for the info.. A full factory set of repair/overhaul manuals came with the car. The info is helpful but none of my questions were answered.

chuck Basics

Very funny. You don't need to see a burned resistor to know it's burned. And a photo of a shorted capacitor will tell you nothing. I asked for a schematic of the speedometer and a source for LED pane lights. That's all I need. Then I will know it all. Thanks!!!

Mrmerlin

Chuck what your missing is that you have a part that no one else knows what you have,
SO your the smartest man in the room.


NOTE the pod panel your working could be a Euro version,
or a USA version,
or a one off version since your working on an early machine.

Your wave circuit could be damaged or shorted or the connectors damaged.


NOTE if you wont give the info requested your chances of getting the correct answer diminish rapidly.

NOTE this is not how to make a good first impression with the people that could best assist you.

Shark2626

Just Google it man, both requests have surely been asked and answered in the Rennlist archives. Read the google results, yes it takes a bit of effort, and find the answers for yourself.

Put what you are looking for in your Google search bar and add Rennlist and 928, then read the links posted in the search results.

Billu

welcome to Rennlist.
Did you say your name was Richard?

chuck Basics

I have only been on this forum for a couple days. I have not had the time to browse the forum very much. You may be right and my answers my be found if I look a bit more. No problem. Thanks.