944 Hooligan

hello everyone,

first off, let me say that this web forum is fabulous! the amount of info available has come in very handy, especially to a recently new p car owner.

i have a question regarding my car's voltmeter. i read recently that the gauge should be indicating at around 14 with a fully charged system. my car actually hovers around 12, so, when i had some recent maintenance completed i had my mechanic test the batttery/connection. turns out the gauge is slightly off - the test indicated 13.75 on his meter. what can i do to get a more accurate reading from my gauge? i have read tons of posts on grounds and cleaning the actual gauge terminals...where is the best place to start?

thanks in advance!!

IceShark

Try the meter, grounds then the postive feeds.

The fact that you are reading 13.75v at the battery doesn't necessairly mean the dash gauge is incorrect. You can have a lot of voltage drop by the time the current runs from the battery, through those skimpy wires to the fuse/relay box and through the fuse relay box then back to the battery through the steel frame.

If you take a meter and measure voltage inside the car you can tell if your volt meter is off. Wouldn't be a surprise if you were droping 1 3/4 volts to the meter through resistance. As an example, some guys only got 10.5 volts to the headlights by the time the current got done running all over creation and down to the bulbs.

The reason adding a supplemental ground from engine block to frame is important is you have a fairly straight shot for current to run through (on the negative side) from the alternator through good conductors of aluminum and copper. But for the components that are getting ground through the body/frame the current is running through poor conductor steel and over to the battery. There is a bottleneck somewhere in the design that causes a fair amount of resistance in these cars' steel bodies as they age.

944 Hooligan

thanks for the info IceShark,

but how exactly do i go about doing this? i do have experience with performing some of my own maintenance and grew up with a father and uncle that were both big block chevy motorheads, but this is a little out of my reach without proper instruction. what do i need to test the gauge and where do i do it?

thanks again...
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

IceShark

You are going to need a free standing meter that will take accurate voltage measurements like your mechanic used on the battery. You can get a cheap one from Radio Shack or a place like that.

I've never pulled the dash voltmeter and am not sure if you could get probes up there to measure in place from underneath the dash or if you would need to pull the instrument cluster. I don't think you can fit up there in place.

So, to start with, I would measure the voltage at an easy place like the dome or glove box light. That will at least give you some idea how much voltage you are losing by the time current gets into the cockpit. One thing to keep in mind is some cars have poor ground connections to the instrument cluster so you may want to pull that anyway.

Anyway, I would first verify that you are losing approximately the same voltage as the dash meter indicates, then make a plan of where you go from there. I can tell you right now that a supplemental ground from the engine block to the frame rail is going to help your system out.

944 Hooligan

[quote]Originally posted by IceShark:
<strong>You are going to need a free standing meter that will take accurate voltage measurements like your mechanic used on the battery. You can get a cheap one from Radio Shack or a place like that.

cool, i figured that would be the place to go

I've never pulled the dash voltmeter and am not sure if you could get probes up there to measure in place from underneath the dash or if you would need to pull the instrument cluster. I don't think you can fit up there in place.

So, to start with, I would measure the voltage at an easy place like the dome or glove box light. That will at least give you some idea how much voltage you are losing by the time current gets into the cockpit. One thing to keep in mind is some cars have poor ground connections to the instrument cluster so you may want to pull that anyway.

do i have to expose bare wire for the meter? is the process of removing the cluster straight forward, or a total pain? how can i find the grounds once it is pulled?

Anyway, I would first verify that you are losing approximately the same voltage as the dash meter indicates, then make a plan of where you go from there. I can tell you right now that a supplemental ground from the engine block to the frame rail is going to help your system out.</strong><hr></blockquote>

how do i add this supplemental ground? while i am at it, should i go ahead and clean all the grounds on the car? replace? where the hell are all the grounds!? i've read some other posts of people running into problems when they tinker with the eletrical system, will doing any of the above have a negative impact assuming i am 100% accurate in my repairs?

thanks for your help so far IceShark, i am already learning , and that makes all the difference.

on an unrelated note, i also have a question about my engine oil light...should i create another post?

thanks!!!! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

IceShark

For the supplemental ground you go to a welding supplier, get a 2 foot section of #4 arc welding cable, and have them crimp on some eye terminals - one end with a 5/16" hole in it and the other with a 1/4" hole. Wouldn't hurt to solder that crimp also.

You run that cable from the front of the engine block to the frame rail ground under the headlight bucket. You will see a bolt with a few brown wires running to it. Clean that area up. There is another one on the other frame rail.

For battery, just follow the cables to where they attach to the car and clean up those spots.

Also you should be looking for green corrosion on the ends of these wires and old cracked insulation. Replace if bad.

You don't have to cut open and expose bare wire to take your test measurements. Just go to where there is a bare spot on the end termial. Search Rennlist, there are complete instructions on how to pull the instrument cluster. On the smaller gauge wires in our cars, negative or ground is a brown colored wire so look for that.

You should be just fine doing all this stuff and it is not particularly complex. Oh, is a very smart practice to disconnect the battery before you go messing with the electrical system so you don't short something by accident.

Post oil light as seperate thread.

944 Hooligan

[QUOTE]Originally posted by IceShark:
[QB]For the supplemental ground you go to a welding supplier, get a 2 foot section of #4 arc welding cable, and have them crimp on some eye terminals - one end with a 5/16" hole in it and the other with a 1/4" hole. Wouldn't hurt to solder that crimp also.

You run that cable from the front of the engine block to the frame rail ground under the headlight bucket. You will see a bolt with a few brown wires running to it. Clean that area up. There is another one on the other frame rail.

For battery, just follow the cables to where they attach to the car and clean up those spots.

Also you should be looking for green corrosion on the ends of these wires and old cracked insulation. Replace if bad.

You don't have to cut open and expose bare wire to take your test measurements. Just go to where there is a bare spot on the end termial. Search Rennlist, there are complete instructions on how to pull the instrument cluster. On the smaller gauge wires in our cars, negative or ground is a brown colored wire so look for that.

You should be just fine doing all this stuff and it is not particularly complex. Oh, is a very smart practice to disconnect the battery before you go messing with the electrical system so you don't short something by accident.


cool cool cool!

any recommendations on what works best for cleaning these spots? is there a product i can put on these terminals to help prevent future corrosion? disconnect both positive and negative feeds to the battery?

when i create my new ground wire for the engine to frame rail, where do you recommend i make the connection on the block?

i found some threads with great info on removing the cluster, and i will begin a new thread for my oil light.

i really appreciate your help to this point IceShark!!
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IceShark

Scrub the corrosion with a wire brush .... if the corrosion is too bad and has walked up inside the insulation you really should chop it out and splice in a new section or replace altogether.

To prevent a repeat you can either spray with silicone spray every year or so, smear on dielectric silicone grease or even apply vaseline (though this will melt and run if it gets too hot.)

Disconnect the negative battery lead first so you don't accidentally short the positive to the body with your wrench.

I tell people to connect the supplemental ground to the top bolt that holds in the upper balance shaft housing or the engine lift ring if you prefer.

Hans

Jason, Shark is right, do it.
Cleaning the grounds will prevent a lot of the electric gremlins you will find in the archives from happening.
I also swapped the ground bolts for stainless ones, the steel ones are kinda rusty after 16 years in a humid marine environment.Most of them are M6x12, obtainable from the local hardware store.
TakeCare