Electrical Gurus - 87' no keyed power
 

My truck died this morning. I coasted into a parking lot and it appeared to have no electrical power to anything through the key. I tried a few times and the lights and buzzer etc. that normally come on when you turn on the key were all dead. The dome light, clock and head lights still had had power. After standing around for a few minutes trying to figure out my next move, I tried again and it started right up like nothing ever happened. I drove it back home and started and restarted it a few times and everything seems fine now.

I plan to dig around this weekend looking for loose wires. Anyone have any ideas what could cause this?

Re: Electrical Gurus - 87' no keyed power
 

Id pop for a new switch.

Re: Electrical Gurus - 87' no keyed power
 

A loose connection.
BTW, 87' means 87 feet. What are you working on?

Re: Electrical Gurus - 87' no keyed power
 

That would be my first choice. Cheap and easy.

Re: Electrical Gurus - 87' no keyed power
 

I changed out the ignition switch on top of the steering column today. Visually inspected the power wire that runs along the firewall down to the starter and everything looks okay. Battery and starter terminals are tight.

Took it for a drive and it died again! No power again though the key. After a few minutes it had power again and fired right up. Anyone have any ideas?

Re: Electrical Gurus - 87' no keyed power
 

Thermal open circuit.
Have you recently changed the battery or starter?

Re: Electrical Gurus - 87' no keyed power
 

No. The battery has been in there a couple of years and the starter about four years.

I have a digital multimeter, but I'm not real good with using it.

Re: Electrical Gurus - 87' no keyed power
 

You'll need an assistant.
While it's not working check that the START wire is getting battery voltage with the key turned to the START position.
Set the meter to DC volts and check from the BAT terminal on the starter to the positive battery post while the ignition switch is turned to the START position. It shouldn't show more than 0.2vdc.

You'll probably find you have loose connections at the block ground or the starter.

The neutral safety switch may be in less than stellar condition.

You can also test connections without a load...
http://www.aa1car.com/library/voltage_drop_testing.htm

Re: Electrical Gurus - 87' no keyed power
 

Thanks Hatzie. I cheated and took it up to a little shop at the front of my neighborhood. They said they found a green accessory wire with a broke terminal. Still not 100% sure if this fixed it, but I will keep driving it and will find out soon enough.

Re: Electrical Gurus - 87' no keyed power
 

After 2-1/2 years of thinking this issue was solved it started doing it again! I was driving down the freeway and the truck died. I coasted into a parking lot and again I had no keyed power. The warning lights, buzzer, radio-everything through the key was dead. After a few minutes, power came back and it started right up like nothing ever happened.

When this happened before, I ended up replacing the ignition switch on the column and put on a new connector at the starter. I never found any loose grounds or anything. I even took it to a shop and they couldn’t find anything. I had to have it towed because it wouldn’t restart and left me stranded on the side of the freeway. When we unloaded it from the tow truck, the damn thing started right up again! I wish it would have just stayed broke so I could diagnose the problem. Lol

I’m thinking about replacing the entire wire and fusible links for the wire that goes from the starter up the firewall. If anyone has any other words of wisdom please let me know!

Re: Electrical Gurus - 87' no keyed power
 

Check your charging system output and check all of the fusible links.

Re: Electrical Gurus - 87' no keyed power
 

Check your wiring harness going through the fire wall for looseness/corrosion and 12 volt power from there to the coil...........

Re: Electrical Gurus - 87' no keyed power
 

I had a caprice wagon that did the same thing. when to leave a friends house one night and it went rrr-rrr than died. no start, power anywhere.

Had it towed home and as it was unloaded, power/lights came back on. once fully down, it started right up again.

Took me a while but found out it was a short inside the battery. replaced with a new optima and all was good after then.

Re: Electrical Gurus - 87' no keyed power
 

I've had the hard plastic fuseable links off the starter do that to me. time to replace them.

Re: Electrical Gurus - 87' no keyed power
 

Those plastic baluns are not the fusible links.
The Fusible link is a special type of wire between those baluns and the starter BAT stud or the J studs on the firewall.
The baluns are molded weather tight covers for the splices between the fusible links and the harness wires.

Re: Electrical Gurus - 87' no keyed power
 

ok I've had connection problems there, replaced them with new fuseable links and no more problems.

Re: Electrical Gurus - 87' no keyed power
 

I like to use a test light - easier than trying to read a multimeter when you are in a tight spot. Start at the battery and move out.

+ to - on the battery
+ on battery to frame, block, body to verify good ground.
Start working your way down the line. Use the frame or body for ground.
Make your way to the fuse block.

Since you are having problems after the key the main things you want to check are:
Is power getting IN to the ignition switch, and
Is power getting OUT of the ignition switch to the proper circuits.

If you are not getting power TO the switch, you need to follow everything from the battery to the ignition switch. If it is going in, but not coming out, you either have a bad connection or a bad switch.

EDIT:
Schematics: http://forum.73-87chevytrucks.com/sm...?topic=11766.0

Looks like:
RED is power into the ign switch
PINK and ORANGE are RUN
PURPLE or YELLOW is START (depending on auto / manual)
BROWN is ACC

Re: Electrical Gurus - 87' no keyed power
 

A test light, while useful in some situations, will not give you the resolution necessary to find this intermittent.
You're either chasing a corroded or damaged connection or you have a bad internal connection in the battery.
This is tedious and time consuming to chase down but it ain't rocket science.

First off, Do a visual check for corrosion or damage. If a cable jacket is lumpy and not smooth the wire has corroded internally and is causing issues. Replace any internally corroded wires. If the jacket is damaged replace or repair the damaged wire and protect it from whatever damaged it.

Do a voltage drop test on each of the cables from the battery to the firewall bulkhead plug. You also need to do a voltage drop test on all of the ground cables and connections.

You need a decent Digital Volt Meter (DVM).

I intensely dislike cheap autoranging meters for voltage drop tests because, unless they are fairly high end (expensive), they tend to jump all over the place and not settle down soon enough to give a good read.

You can set the range on some inexpensive autoranging meters like the Extech 330 but your meter needs to have a range button to do it.

The meters I like to use on this kind of stuff are the old Dinosaurs or new $40 cheapies with several DCV settings say 200mv, 2v, 20v, 200v, 1000v and not just one setting for VDC.

Whatever you get for a meter get a decent set of probes. Look up Pomona 5519A. Those Pomona probes are generally around $20 but they will outlast several cheap meters. The probes that come with most meters, including my Fluke, are darn near worthless. The set that came with my Simpson 260-7 Analog meter had loose internal connections that made the readings float. The set that came with my Fluke 117 were no better.

Set the meter on 20VDC or whatever range is closest to but more than 14.5VDC and check the voltage between the lead posts on the battery. It should be 12.4-12.6v if it's in good shape and fully charged. You need the battery to be fully charged to run a voltage drop test so if it ain't fully charged put a charger on it and make it charged.

On a Top post battery check the voltage from the Neg post to the Pos battery cable lug and the same from the Pos post to the Neg cable lug. It shouldn't vary more than .01v. If it reads a difference of more than .03v clean the connections and re-test.

If I have the original side post battery I assume the connections are corroded and disassemble both Pos and Neg terminals... pull the bolts and strip off the non-molded protector shroud, clean all parts thoroughly with baking soda and brass brush and lots of water, and re-assemble with protectant.

Turn the ignition on and turn on the headlights.

Set the meter on 2VDC and probe from the Neg lug to the Ring terminal on the alternator bracket. There should be less than 0.03vdc.
Probe from the ring terminal to the ground bolt on the alternator bracket. It should be less than 0.01vdc.
Probe from the alternator bracket battery cable bolt to the intake. Again it should be less than 0.01vdc.
Probe from the intake to the firewall ground strap stud. It should be 0.01vdc or less.
If the voltage reads higher on any of these steps remove the connections, clean them, re-install with protectant and re-test. If they still read high replace the wire being tested.

Now start along the positive battery cable to the starter, from the starter to the J-studs on the firewall, from the J-studs to the Alternator BAT stud and to the bulkhead plug... You should see 0.03vdc or less on each step.
Again, If the voltage reads higher remove the connections, clean them, re-install with protectant and re-test. If they still read high replace the wire being tested.

Look the fat 12ga Red wires over inside the cab.
Are the 1/2" blade terminals on the ignition switch cruddy and burnt looking?
Do you have any obviously damaged wires at the fuse block, ignition switch, or the bulkhead plug. DO the terminals look overheated or corroded.
Fix whatever ain't right.

Some people allow up to 0.1vdc drop on each step but it's additive. Assuming the battery is 12.2vdc and the battery to cable and cable to starter and starter to J-Studs and J-Studs to bulkhead plug all have 0.1vdc drop the voltage at the bulkhead plug will be 11.8vdc and points inside the cab to things like the ECM will be even lower. You will get away with 11.8vdc but it erodes your safety margin and the corrosion or loose connections causing it will get worse over time. The ECM doesn't like low voltage.

Re: Electrical Gurus - 87' no keyed power
 

Thanks for the suggestions guys. I spent a couple of hours crawling around under the truck last weekend looking at wires and I don’t see any obvious bad wires or connections.

Hatzie, I do own a digital meter that I picked up a while back at Autozone (pic attached). I would be lying if I said I knew how to use it, so thank you for the thorough explanation! Looks like it does have the DCV settings. I just ordered a set of those Pomona leads off of Amazon. I’m determined to figure out the problem because I’m afraid to drive the truck any where now. :lol:

Re: Electrical Gurus - 87' no keyed power
 

I’ve been playing around with this multimeter trying some of the tests Hatzie suggested. My negative cables tested okay.

On the positive side, I changed the ring terminal connector on the positive cable lug that runs from the battery to the alternator just because I didn’t like the way it looked. Someone had put a new connector on it with a splice. I cut out the splice and put on a new terminal. The test from the positive stud on the alternator to the J-studs on the firewall was reading .031vdc. After testing for about 15 or 20 minutes with the head lights and key on, my battery lost enough power that it wouldn’t start the truck. I had just charged it overnight, so I decided this battery was weak and went and bought a new one. With the new battery installed I redid the test from the positive stud on the alternator to the j-studs on the firewall with the key and lights on. With the new battery I get a reading of .001. It’s interesting that I’m getting a better reading with the new battery!

I guess time will tell if I fixed the problem with it dying and losing keyed power, but I think I needed a new battery anyway.

Re: Electrical Gurus - 87' no keyed power
 

Good luck! Hope the battery is all it was. I had a number of electrical gremlins getting to the point where I could drive my truck and like you, wasn't too confident in my multimeter skills. Help from Hatzie and others with suggestions of how to test often got me looking in the right direction even if the suggested test showed no issue. Its good practice and should help you have more confidence if you check all those points.

Re: Electrical Gurus - 87' no keyed power
 

Thanks Rick! I’ve learned a lot just in the last week. I read Hatzie’s post several times and watched some YouTube videos. I just ordered some leads with alligator clips for the multimeter also. I figure I can leave one end clipped at the battery while I crawl under and check the wires at the starter etc. without having to have someone hold the other end.

They had a record at the parts store of when I bought the last battery. It was purchased in 2014, so it’s been in there the whole time I’ve had these issues. I never heard of a short within the battery before this. I sure hope that’s all it was.

Re: Electrical Gurus - 87' no keyed power
 

My truck died again on Saturday. This time I had a multimeter with me. It was getting over 12 volts to the starter, over 12 volts to the lug on the alternator, but 0 to .5 to the stud on the firewall. So I think my problem is between the starter and the stud on the firewall. I started shaking wires around and it started and I was able to drive it home. The terminal at the starter has already been replaced, but I may replace it again. The rest of the wire runs behind the block and is difficult to see.

What does the small gauge wire on the starter do? I’m suspicious of that wire because it looks like it’s been repaired before, but I’m not sure if it would cause me to lose power to everything.

Re: Electrical Gurus - 87' no keyed power
 

The J studs get power from the 3/8" starter BAT terminal. The 3/8"ring terminal is attached to a 6" long 14ga fusible link that's attached to a10ga wire running up to a ring terminal on the 1/4" j stud.

I assume the small wire you're asking about is purple and attached to the #8 S terminal on the starter solenoid... that's the CRANK wire.

Re: Electrical Gurus - 87' no keyed power
 

Thank you Hatzie. Do you think the fusible link could be bad?