Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 914 & 914-6 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Dec 1969
Location: fullerton, CA
Posts: 9
Tachometer woes

I've been working on my 914 72' off and on for the past 6 months. I've done so many things to my car that I forgotten where everything belong. But like one big massive jigsaw puzzle I think I got everything in place, except....

the tachometer, it doesn't work, and my emergency brake indicator keeps flashing.

I've been hunting through the Haynes manual but the electrical diagram to the tachometer is so vague that I get confused when I look at it.

Can anybody out there explain to a novice like me how the tachometer works? and a few things I can look for when trying to solve my problem?

Old 06-07-1998, 12:12 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Author of "101 Projects"
 
Wayne 962's Avatar
Hi there Howard,

Going into the tach, there is power, ground and signal. The signal wire should be black and purple, the ground wire should be brown.

This purple/black wire goes down the center tunnel to the terminal on the coil that is attached to the points. The tachometer is driven off of the points signal.

The blinking brake light may be caused by the switch in your master cylinder. Check out the explanation at:

http://www.pelicanparts.com/914/914QA/914Q_brakes_e_light.htm

Hope this helps,

Wayne
Old 06-08-1998, 07:16 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Dec 1969
Location: fullerton, CA
Posts: 9
Oh, well when I took out my transmission and put it back in, there were a few wires I didn't know where they belong.

I have a set of three wires going to my coil. One green the other two are black comming from the relay board. The green one I have connected to the negetive part of the coil and the other two are to the positive.

Is the tachometer wire any of those three wires? and Do I have those three wires connected right?

The blinking flashing break light. When I changed my transmission I didn't touch the brakes. Is it possible that this is still the case?

Howard
Old 06-09-1998, 07:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Author of "101 Projects"
 
Wayne 962's Avatar
The best advice that I can give you is to check out our electrical diagrams:

http://www.pelicanparts.com/914/914parts.htm

They are for the 1971 model, but there differences should be very minor. This should help you at least get going in the right direction.

And, yes, if you look closely, I think that you will see that one of those black wires is actually black & purple, and controls the tach signal...

Hope this helps,

Wayne

P.S. Don't quote me on this, but I believe that the green, and two black wires go to the negetive terminal, and that the red/black one goes to the positive. It sounds like you might have these switched. Check the electrical diagram...
Old 06-09-1998, 12:43 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Administrator
 
Dave at Pelican Parts's Avatar
 
Join Date: Dec 1969
Location: Silly-Con Valley
Posts: 14,062
Garage
Send a message via AIM to Dave at Pelican Parts Send a message via Yahoo to Dave at Pelican Parts
Definitely don't quote you on that, Wayne. ;^)

The fatter black wire is "switched power", and should get +12V when the ignition is on. This wire gets connected to the "+" side of the coil.

The green wire comes from the points by way of the condensor. It gets grounded when the points close. It goes to the "-" terminal.

The thinner black wire should have a purple stripe--it's pretty dark, so look carefully. The tach uses the opening and closing of the points as its signal, much as the coil does. This wire hooks onto the same terminal as the points wire, the "-" one.

If you have a Bosch coil, you'll see numbers on the cap of it. One of the side terminals is labeled "1", and the other "15". (I think the big center terminal is "4", but I'm not sure on that.) The Haynes diagram has little numbers where the wires hook up to the coil. The numbers on the diagram correspond to the numbers on the coil. Cute, huh?

The car will run with the coil hooked up backwards, but not very well.

--DD
Old 06-10-1998, 12:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Author of "101 Projects"
 
Wayne 962's Avatar
According to the electrical diagram:

- Green goes to -
- Black/purple goes to -
- Black (from points) goes to -
- Red/Black (switched power goes to +)

The 'fatter black' wire should have a red stripe down it's side. Being in the engine compartment, sometimes the coloring is hard to see with all the dirt, etc. on it...

Again, check the electrical diagram and you should be fine...

Thanks,

-Wayne
Old 06-10-1998, 08:42 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Administrator
 
Dave at Pelican Parts's Avatar
 
Join Date: Dec 1969
Location: Silly-Con Valley
Posts: 14,062
Garage
Send a message via AIM to Dave at Pelican Parts Send a message via Yahoo to Dave at Pelican Parts
Actually, Wayne, you're misinterpreting one little bit of the diagram. The black wire from the coil back to the distributor is the big THICK one from the center terminal of the coil to the center terminal of the distributor cap. The green wire is the one from the points. The black-and-red is indeed the power supply for the coil. Some time between 71 and 74 (my car), the wire was changed to all-black.

Anyway, back to the first question. There are two switches that affect the brake light in the combo gauge. If either of these switches is closed, the blinking light goes on.

One of these switches lives inside the brake master cylinder. It closes when there is a difference in pressure between the two brake circuits, such as when you bleed the brakes. There may be a button on this switch which is covered by a rubber nipple. If so, push the button (just push the nipple) to re-set it. You can see the switch easily if you crawl under the car and remove the steering rack cover.

The other switch lives underneath the handbrake lever. The switch is closed UNLESS the lever is all the way down, which pushes on the little "button" opening the switch. The handle may not be pushing the switch correctly, or the switch or wiring to the switch may be faulty.

Good luck with the troubleshooting!

--DD
Old 06-11-1998, 03:07 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Dec 1969
Location: Lac La Biche, Alberta, Canada
Posts: 951
Dave, a quickie on the brake warning light. On my 72, I replaced the switch at the m/c when I rebuilt it. The switch at the hand brake is operational. When I turn on the ignition switch, the brake light blinks at about half intensity. It has done this since I have owned the car (about 3 years). When the car is started, the light goes out unless my hand brake is on. The half bright brake light seems to be back fed by the diode in series with the gen light. The diode is ok and everything else works fine. I also checked the diodes in the alternater which were all ok. Is this the way it is supposed to work or do I have a problem?
Old 06-12-1998, 07:06 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Author of "101 Projects"
 
Wayne 962's Avatar
Hi there Tim. No, that half-on brake light problem is not very normal. If you suspect something possibly with the alternator, then try unplugging the wire harness from the relay board in the engine compartment, and seeing if you still have the same problem. I know that the hazard lamp is supposed be lit slightly when the lights are on, but that is the only light I can think of that would be lit any less than full strength.

Don't you love electrical problems.

-Wayne

P.S. Tim, I got my tranny working a lot better, look for the update to the synchro article!
Old 06-12-1998, 08:14 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
Join Date: Dec 1969
Location: Lac La Biche, Alberta, Canada
Posts: 951
Yes, the light goes out if I unplug the alternater from the relay board with the engine stopped and the ignition on. The charging system has always worked well. As I mentioned earlier, the diodes in the alternater are all ok. I have a spare regulator I could try. Actually, now that I think about it, I really really like the way the brake light comes on at half intensity before I start the engine!!!!
Old 06-12-1998, 08:24 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
Join Date: Dec 1969
Location: Lac La Biche, Alberta, Canada
Posts: 951
If I keep fixing it long enough, eventually it will prove someone right by being broken. (yes, light goes out if I diconnect the alternater plug from the relay board).
Old 06-15-1998, 07:46 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Author of "101 Projects"
 
Wayne 962's Avatar
How do you know that the alternator is good? There are a few diodes in there, one may be bad while the others are good. If you plug in another 'good' alternator, does the problem still ocurr?

-Wayne
Old 06-15-1998, 10:24 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
Join Date: Dec 1969
Location: Lac La Biche, Alberta, Canada
Posts: 951
I think the diodes in the alternater are an albatross (BTW, I rebuilt it two years ago and checked the diodes with an ohm meter). Look at page 150 of Haynes at how the diode is connected from the alt lamp to the brake warning light. Now compare it to the diagram on page 148, and notice the diode is missing for the European version as is the m/c switch. Is it just possible that this diode is doing just what it is supposed to do, and that is provide a fail/safe that the brake warning light really works?
Old 06-15-1998, 11:37 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered User
 
Join Date: Dec 1969
Location: fullerton, CA
Posts: 9
I would like to thank the people who responded to my post.

I just wanted to do a follow up on how I fixed my problem.

Dave was right, I messed up the wiring on the coil there are supposed to be two wires on the negetive (one green, the other black and something, one wire on the positive (black and red), and one big thick black wire in the center of the coil.

The emergency brake light. It turns out that it wasn't any of the problems that you guys thought it was. It turns out that my alternator had gone out, and when I replaced the alternator (which was a ***** to do for a first timer) the emergency brake light stopped blinking.

I wonder what other electrical problems are signaled by the emergency brake light.

Well Take Care,
Howard.
Old 07-01-1998, 07:39 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
Registered User
 
John Rogers's Avatar
 
Join Date: Dec 1969
Location: chula vista ca usa
Posts: 5,207
On our 1987 911, the brake warning light acts like a current flow indicator, so that if the alternator is not putting out enough voltage to force current flow to the battery, it comes on. I think our 914 is the same way and not suprisingly, this does not seemed to me mentioned in any manual, although there was an excellent writeup about a uear ago in Pano on how elec systems worked and it was mentioned.
Old 07-03-1998, 06:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 10:41 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.