SwayBar

Most multimeters I've seen can measure current:

http://us.fluke.com/usen/products/sp...(FlukeProducts)

You are missing the point. All one is concerned with is tracking down where the current draw is going to, while not really caring exactly how many mA are being drawn. If a fuse is pulled and the current draw decreases from whatever it was prior to pulling the fuse, a potential problem area has been discovered.

Carl Fausett

I have seen those fail ( I sell them) in only two situations.

1) the installer put them in the positive cable, not the negative side as instructed. Too much current draw on the pos side.

2) the last person to turn the green **** down did not turn it down tightly, but softly (I did that). The contact area was too small, and it overheated just as you have described. I replaced it, and learned to turn it down TIGHT for the year, and to remove the green screw during storage season. Have used it for several years without a problem.

Not as good as a race-type kill-switch to be sure - but the kill switches are meant to be switched on-and-off many times. Instant on, instant off. But these cost less, do not require drilling holes in the car to mount, and serve their function well.

John Veninger

??

Alan

Humm - yes... well....

All the current that goes in one comes out the other... really. To your other point - yes a likely cause - that and regular cleaning are probably both important.

For a regular under hood battery mount I think these would be acceptable - not as quick as a switch but pretty close...

Where we have our batteries (especially if you have a spare wheel installed) - whats the point? - it will take you minutes to get to it... putting such a screw down at the battery GP makes more sense - didn't someone say that they found a knurled & studded **** that fits on the later cars that don't have the wingbolt?

Alan

StratfordShark

That's exactly what I was thinking Alan. It's much more effort to get to the battery than to undo the ground strap. I would like to mount a kill switch though to save bother of removing tool kit and lifting carpet though this is more an issue if car is to be left for a long time. When I'm working on it and know I'll need to disconnect battery then I leave the ground strap exposed.

SteveG

GAZ: Generally I would not jump or charge from a battery pack. RE computers, I don't know enough about circuitry and charge rate. Are some packs sophisticated enough to control amps going to the circuit?

RngTrtl

What you are refering to is an AC (alternating current) ammeter. The reversing of polarity during current flow induces a voltage in the clamp probe. When you hook it in to the multimeter, the probe ports have a determined resistive value and the voltage drop across that resister is used to deduce the current flow through the leads and thus through the ac circuit that the clamp probe is clamped around.

VehiGAZ

Thanks for the MM primer... it's good to know that I can measure DC amperage with my MM!

To your point, swaybar - the mechanic was just trying to see if there was an excessive drain on the battery, but I see how your method would work very nicely to narrow down the cause if a drain was found.

I see your points about mounting the disconnect switch in the spare wheel well - still too much stuff to move and disassemble to be worth it.

Ron_H

Sway Bar:
Thanks for your thoughts. I have spent hours with a multimeter doing exactly what you described. Some relays were changed. The alarm system was disconnected. The gremlin persists. It is elusive. Now it appears to be gone. It will probably return. However the real problem started when I experienced an electrical fire after a shop had worked on the car and passed some wires through the firewall to a device in the engine compartment. One of the grommets in the firewall worked its way loose and a cluster of burned wiring was found at that point, obviously having chafed against the sheet metal of the firewall and shorted out. After many thousands of dollars later and the replacement of what was believed to be all the burned wiring, the gremlin persists. Of course the belief is that not all the burned wires have been found. The dash was removed once in the search, but I just don't want to bother with it again. I simply turn the battery off at night. Yes, I get poor mileage, but I didn't buy this car to compete with a Honda or Prius, and my right ankle just loves to twitch especially on open roads. I just want to enjoy the ride. I have become weary of the chase for this freaking elusive gremlin. I would rather sit in my garden and watch the flowers grow than chase electrical gremlins. And.......I know where to find another '86.5 in great shape with much less miles........so maybe I'll just throw this one away and buy that one soon.

bd0nalds0n

The green thumbwheel pictured above fits perfectly in the hole where the groundstrap attaches to the body behind the toolkit. No need to put the disconnect at the battery; you can put it where it's easily accessible.

docmirror

It doesn't. I was only mentioning that the car has to be fully warmed for the characterization to complete. By the time the O2 sensor is in closed loop mode, the cats will be fully hot.

If you're intent on using one, this is preferred. Put it in the back, under the tool tray. The key comes out, and it has a solid spring loaded contact. I use them on RVs.

http://cgi.ebay.com/ebaymotors/MARIN...QQcmdZViewItem

Carl Fausett

On a DC circuit, its common to put the switch in after the load as you can use a smaller and less expensive switch. Example: If I was putting a swicth on a fuel pump that draws 15 amps, I would need a bigger swicth if the switch is on the supply side before the fuel pump, but I can use a smaller (read less expensive) switch on the negative side after the load as some of the amperage has been consumed (converted to heat energy) and the load at the switch is smaller.

An examination of the fuse/relayy panel will show this - that many of our relays are in the ground circuit, not the supply side. Standard Operating Procedure.

You can even use smaller gauge wires on the negative (return) side than on the Positive side - and if you look at your battery - they do. This is where the battery-isolating break switch should be installed.

Alan

Carl - sorry - but stick to engines - you don't know what you are talking about here...

Porsche very rarely puts relays in the ground path... when they do its for convenience nothing more. The battery strap AWG is related to voltage drop - longer = bigger. anyway on my car the ground strap is probably the same total AWG.

Alan

docmirror

Carl, I love ya bro, but don't go here. You would need to study electron flow for a while to get the concept. A quick check of this 'theory' of negative side having less - em, amperage. If this were true, the negative side of the battery would only need to be a 28 gauge wire, cause most of the energy of the circuits would be 'consumed' by the combined loads. Energy is niether consumed or created, only transferred from state to state. next, If you want to get picky, the negative side of the circuit is the 'supply' side(we're not talking holes here). So, there are actual, physical electrons moving out of the negative terminal of the battery, flowing through the car chassis, and marching up the legs of the various ground points to the various loads. It's a tough concept sometimes, but that's physics for ya.

dr bob

For those that have been through the primary positive cabling--

It seems to me that the disconnect needs to be in the circuit between the battery circuit and the CE panel, but not disconnect the starter or the alternator. For SCCA, you need to --completely-- isolate the battery, but for the folks who just want to cut off all loads during storage, we can leave the starter and alternator connections intact. Ditto the two S4+ fan primary leads at the battery-- they can stay on during storage too IMHO. So, to the question: Is there a point anywhere near the jumpstart terminal where the disconnect switch will fit into the circuit as I described? From a casual look, the positive is routed battery to the starter solenoid, then on to the jump-start terminal. It also looks there's a feed from that main connection at the starter to the ABS power point. Where does the alternator connect in this scheme? It wouldn't bother me a bit to mount a switch inside the fenderwell or someplace similar, or a jumper on a two-pin terminal that would take 100 amps continuous. I'm thinking along the lines of one of those snap-connectors used on high-current UPS and forklift batteries. Hell of a theft deterrent tool too. Doing the disconnect in this part of the circuit avoids accidental alternator and smart module damage if the circuit is opened while the engine is running.

Thoughts? Alan? Other gurus?


-----


I have the in-circuit gremlin-tracer light bulbs and fuse replacers, DC amp-probe and ammeters, test lights, jumpers, etc. all ready in case my car ever shows signs of excess parasitic draw. So far they are gathering dust, but within sight of the car so it knows not to mis-behave. Meanwhile, the maintainer goes on if I know I'll be gone more than a week, but the car also started easily after a couple unplanned six-week 'vacations'. Daring the gods, Myron Volt, Albert Amp, and Jimmy Watts when I say this-- So far so good!