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ZAMM Fanatic
2,730 Posts
Discussion Starter #1 (Edited)
I'm gonna call this post "Lesson #3 in Voltage Dropping" because it showed me the IMPORTANCE of voltage dropping starting circuits instead of just throwing parts (new battery, new starter, new solenoid, new wiring..) at a vehicle that won't start.

Friend of a friend owns a '83 Subaru Wagon 4x4. Said it wouldn't start, asked if I'd fix it.

"Of course!" friend #1 has done me endless favors.

I go over, turn the key, and nothing. But I turn the headlights on, and they're nice and bright, so it's PROBABLY not the battery.

I get under the hood (leaving the car in neutral, of course) and use a screwdriver to jump from the solenoid terminal to the starter terminal. Starter spins.

So I now know I've got a good battery AND a good starter.

I reach down, under the starter, and pull off the wire to the start terminal on the solenoid. It's hard to reach. I get it just close enough to put a meter on it, and have a friend turn the keyswitch. 12.4 volts.

So I've got a bad solenoid. It's got signal from the keyswitch, and 12v from the batterry and the starter is good.

Except I'm wrong.

Siince the solenoid is integral to the starter, I run into town and pick up a new starter. (At NAPA, the ONLY place I'll buy a starter, not the cheap Chinese starters at AutoZone, etc.)

Put the new starter in, hook up the wires, reconnect the battery, turn the switch and...NOTHING.

You see, 12.4 volts on the start terminal MEANS NOTHING if there isn't a load connected.

Every strand in the wire could be frayed except one and still see 12.4 volts.

Or, more likely, the contacts in the keyswitch are worn out, burned, corroded from 20 years of use.

Voltage simply DOESN'T COUNT if there isn't enough AMPERAGE to back it up, which is why you have to VOLTAGE DROP circuits WITH THE LOAD CONNECTED.

I run a piece of scrap wire from B+ to the start terminal on the solenoid and she spins like crazy.

It wasn't the solenoid, it's a worn out keyswitch. (or damaged wire from switch to solenoid start terminal. but it looks ok)

Had I PROPERLY VOLTAGE DROPPED the keyswitch circuit, measuring the voltage AT the start terminal, WITH THE WIRE from the keyswitch connected, I probably would have only seen around 6 volts. Not enough to engage the solenoid.

I didn't do that because it was hard to reach, and I ASSUMED if I saw 12.4 volts on it, unloaded, that was indication enough the keyswitch was working.

So it's off to town for a new keyswitch.

Of course I could "Justify" the new starter with, "well, the old one was 20 years old, probably time to replace it anyway, blah blah, blah.

The point is in the 2 minutes it would have taken me to correctly VOLTAGE DROP the solenoid circuit, I could have savedd the customer the $100 for the new starter they didn't need.

And this is how TOO DAMN MANY auto shops in America operate, because they don't kknow how to properly voltage drop the THREE, yes THREE circuits associated with a starter.

1) B+ to Solenoid
2) B- to starter (making sureyou have a good ground)
3) B+ to start terminal on solenoid THROUGH keyswitch

The "typical" mc or auto customer goes in with a no-crank, the battery gets tested (hopefully LOAD tested) and then a new starter gets "hung."

If that doesn't FIX it, THEN they begin diagnosis, the diagnosis I should have done UP FRONT.

If the car comes back 2 days later, THEN the charging system is tested.

Folks, if your mechanic (tech) is never charging you for diagnosis time, then they're simply GAMBLING that this or that part is going to solve your problem. When it doesn't, it's EXCUSE CITY.

I probably don't need to tell you WHO PAYS for those parts that didn't solve the problem. You've probably bought SEVERAL if you've owned and had many cars repaired over the years.

It's the freakin EXCUSE OLYMPICS when proper diagnosis is not performed BEFORE replacing parts, known disparagingly as "parts-hanging"

Iknow this because the shops I've worked in, a MAJORITY of the techs didn't know how to correctly voltage drop a circuit. They were parts-hangers.

And some of these guys have been repairing vehicles their entire lives!

And OldDeadEye, since you've claimed I never actually worked in a shop, feel free to give Mountain Mechanical in Durango Colorado a call, or Economy Nissan (ask for Jeremy), or I may be able to find you a pay stub from what was then New Country Ford. (Mtn Mechanical's lead tech, Ed, DOES know how to voltage drop circuits). Oh, and there was AJ Auto (now gone) where Rick Cowherd is the guy who TAUGHT me how to voltage drop circuits, (something I DID NOT learn in 4 years of Electrical Engineering) but I didn't work there, I just hung around, cleaned the bathroom, took out the trash, brought bagels, etc. IN RETURN FOR REDUCED REPAIR CHARGES and the chance to learn how a shop diagnoses cars and MAKES MONEY by specilizing in certain problems, certain makes, and avoiding certain customers.

(You know, the ones who diagnose it themselves and bring in parts they bought on the Internet, :coffeescreen:

Bottom line is if you don't know how to correctly and QUICKLY diagnose malfunctoning electrical circuits by VOLTAGE DROPPING them, (2 minutes per circuit if they're accessible) you've got NO BUSINESS repairing bikes or cars with electrical problems. "Hanging parts" is no substitute for CORRECT diagnosis. The CUSTOMER is the one who gets screwed from a failure to DIAGNOSE problems.

I've pushed Voltage dropping on this forum till I'm blue in the face, and if you'd rather just buy unnecessary batteries, starters, solenoids, than learn how, all I can say is "go for it!"

Now, Warren's 2004 Jeep Liberty is stumbling on acceleration. I'm guessing fuel pump, fuel pressure, Throttle Position Sensor, or perhaps unmetered air from a cracked snorkel between the MAF and the manifold. Other than sending him to Autozone to check fuel pressure (hoping it has a Schraeder valve on the fuel rail), who's got some ideas. I'm not in Phoenix and can't get my hands on the car. It's throwing some ignition codes and he has INSISTED that we HANG PARTS in the way of six new Coil-On-Plugs, despite my .....vehement arguments that hanging parts is NOT HOW YOU FIX CARS!

Who's got some ideas, things to test. (Normally I'd go to IATN.NET and post a case, but...thought I'd give everyone here a shot at it before I get on the Kawasaki, ride down there and DIAGNOSE it properly.)

Retired twice: Navy and as a govt contractor
14,301 Posts
Without the pushback to ODE this is an example of one of your good and informative post. Electrical and I do not get along so I appreciate post like this.

43 Posts
Typically I can't afford new parts so I stumble through every possible thing it couldn't be before I happen apon some sort of cobbled half ass this "diagnostics"? :biggrin:

This is good. I don't have a shop to hang out in Wade, I'll be tuning in for more.

It's all fun and games until someone loses an eye
8,665 Posts
Without the pushback to ODE this is an example of one of your good and informative post. Electrical and I do not get along so I appreciate post like this.
Hell, I don't mind the jab, and it's fairly informative (at least what I read, it's a bit long winded).

Except for the part about the starters. Duralast starters are rebuilt by Remy as are Ultima (Oreilly's brand) and I believe you can buy Bosch from all three. I don't use NAPA anymore. I used to be a Napa car care center and they did have superior parts at one time, until one day I was shipped a power steering pump and the label was half pulled of. Started checking around and they were going to the same crap Oreilly and Autozone carried, but charging more cash. Right under the Rayloc sticker was a A1 Cardone sticker, which was what I was trying to get away from. (And I hate to say it since my sister in law works there, but their service in Norman sucks.)

It's all a crap shoot with replacement parts. I've pulled electronic components out of Autozone boxes that had Delco, Ford, Mazda etc. etc. stamps on them. The only constant is BWD and their stuff isn't what it used to be.

American Legion Rider
23,527 Posts
I used to only go to NAPA myself just to get the best. So I thought. I don't remember exactly when it was but at some point I noticed their parts were no better than the rest. I just figured, China strikes again. Now I've been getting OEM and paying through the nose. And I'm not sure that route is any good anymore. Psychologically I think I'm better but not so sure on some parts. Luckily I don't need stuff that often though.

Aging & Worn
4,516 Posts
Yesterday, I had the chance to have a fella give me a lesson in Electricity. I must've skipped those classes in school, so I listened intently............

Apparently there are these (let's call em) things called "Watts." Inside each one, there lives Amps and Volts.

Amps like to ride on the backs of Volts, and if some of the Volts are dead, the Amps can't get out and do what they do.

So, a Battery, that shows good for Amps, but not for Volts, is a battery that can't start the bike, because the Amps don't have a way to get the job done, without an Amp to ride on.

Sorta like being in the Calvary, without having a horse.

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