Electrical Gremlin/s...need help, please.

[Wishmeluck]

I have an 84' 351w Ive been working on and trying to get back on the road. Last week I went to put things back together and none of the dash lights would work, the blinkers dont work either but I could hear the flasher click for a short while, and the blower motor was intermittent. In all my searching I did find/replace a fried connector for the now new blower motor. Long story short I eventually decided to pull out a multimeter (two actually, to make sure the first one wasnt messed up) and test the fuse box to see where power was/wasnt. This is where it gets interesting...I pulled all the fuses and removed all the flashers and do-hicky's. Theres 12v+ to all the propper supply side terminals in the fuse box (not the interesting part). The load side of the terminals (interesting part)...When in the run position, a handful of the load side fuses register 5-6v in the morning, and the remaining register something under 1v. As the day wheres on and gets warmer the voltage drops with most of the load side fuses registering 0v and the ones registering 5-6v drop down to somewhere around .2-.5v. Then overnight the voltage magically goes back up to 5-6v and starts all over.

I have torn this thing apart and I can not for the life of me figure it out. I have taken the dash off and exposed wires. I chose to trace the brown/org blower motor wire and within a short 3' section, one end completely disconnected from everything just hanging there and the other connected to its own individual spot not touching anything in the fuse block, and it STILL registers 5-6v in the morning, as do a couple other load side fuse spots. Ive looked at wiring diagrams and they dont have any grounds in common and according to wiring diagrams the high voltage load sides are completely seperate circuits.

Things Ive done:

- disconnected every single connector I could find on the rig and cleaned any corrosion/dirt, checking for voltage changes as I went...didnt fix it.
- repaired/replaced any exposed wires...no change.
- disconnected all the ground connections, cleaned, and reattached...didnt fix it either.
- added additional grounds...frame to block, body to block, body to frame...no change.

Im stumped. As it sits right now the only connections are the battery, ingnition switch, fuse block (no fuses or do-hicky's though), and the gounds. And its doing the same thing. What am I missing???

 

[wyo58]

Wish,
There is one thing that is connected still, your alternator and regulator. I have seen shorted diodes in the alternator/regulator bleed voltage. You might try and disconnect it and test your voltages again.

 

[johnnyreb]

Are the ground wires new or old wire? If OLD maybe they are worn out. How about the battery cables and SIZE? The starter and light switch. If its been sitting awhile they will go bad.

 

[Tiha]

Good Suggestions so far.

It could be a bad/dirty power supply to the fuse box. Could also be a bad ground. A corroded connection, or corroded wire will show voltage but not handle loads.

Also as the bad/weak connection heats up, resistance goes up and voltage will drop farther.

Maybe as a quick test use a jumper wire or jumper cable to supply 12v to the fuse box directly and see if that corrects the problem.
If it does, you know where to look.
If not Then maybe try creating a new ground from body/dash to battery to see if that changes anything.

 

[Motech]

This is where volt drop testing is king.

It sounds like you have resistance in your voltage supply. Usual power supply here obviously begins at battery positive, then continuing through the fusible links at the battery positive side of the starter relay solenoid.

Here's what I'd like you to do with your DVOM:

• Red lead to battery positive, black lead probing your powered up fuse load side
• Should see under .20 volt.
• If higher, this is your power side "Volt Drop"

(As you've measured 5-6 volts there, I'm expecting you to see a 6-7 volt drop there, and I'll assume this going forward)

In order to pinpoint the source of this volt-drop (which is resistance), you'll need to backprobe the circuit(s) until your voltage goes down. So next:

• Probe the power side of same fuse.
• If volt drop falls to .09 volt, the resistance is between there and your last measurement (in this case, right there at the fuse itself)

That's as unlikely as it sounds, so if you measure the same 7 volt drop there, just take black probe way back and measure at the source:

• Probe between battery positive terminal (red lead) and the threaded positive terminal stud at solenoid relay (black lead)
• Still 8 volts?

Then your resistance is in that battery positive cable/terminals.

• At or under 0.20 volt?

Continue probing downstream.

Next probe battery power input at bulkhead connector, the big one in firewall that passes through and feeds fuse panel inside cab.

• Under .2 volt?
• Probe same wire at other side of connector inside cab.
• 7 volts?
• BINGO

Your resistance is in the connection between inner and outer bulkhead pass-through terminal(s). Dismantle and correct as necessary.

I'm not saying that this is where your problem is, because frankly I don't know. Furthermore, you might need to load the circuits up a little bit more to get accurate results, and turning on headlights should do that. Or extreme case scenario, crank the starter every measurement you take. Frankly though, if you're only getting five or six volts at the output side of the fuse with key on engine off, then your drop is going to show up key on engine off.

If my explanation is not too clear, Google "volt drop testing" and view whatever YouTube video explains it better than me.

Here is an example of volt-drop testing both positive and negative sides of a component individually.



(Leads are opposite my description, which would generate accurate, but negative values)

Whatever you choose, once you achieve successful results with this method, you will be hooked on volt drop testing forever, and the more you use it, the more you will come to see how simple it really is.

Oh, and it works on both legs, positive and negative sides. Jus hook DVOM black to battery negative and probe ground points with DVOM red, crank starter and check value.

If under .200 volt, you're done. You've confirmed ground integrity if every circuit between test point and battery. No more guesswork needed, no more removing and cleaning up grounds needed, that side is done, and all your grounds are good.

(The reason I focused on positive side to begin with is because you've already measured a pretty significant voltage loss that's your fuse)

Good luck.

 

[Motech]

One more thing...

I believe you're going to find your problem is in the fusible links at the starter solenoid relay. In that case, you may measure a good volt drop of .100 volt between battery positive and solenoid positive, then a high 7 volt drop between battery positive terminal and power input at firewall bulkhead connector.

In that case, it will likely be in one or more if the fusible links coming off solenoid.

 

[L\Bronco]

This is where volt drop testing is king.

It sounds like you have resistance in your voltage supply. Usual power supply here obviously begins at battery positive, then continuing through the fusible links at the battery positive side of the starter relay solenoid.

Here's what I'd like you to do with your DVOM:

• Red lead to battery positive, black lead probing your powered up fuse load side
• Should see under .20 volt.
• If higher, this is your power side "Volt Drop"

(As you've measured 5-6 volts there, I'm expecting you to see a 6-7 volt drop there, and I'll assume this going forward)

In order to pinpoint the source of this volt-drop (which is resistance), you'll need to backprobe the circuit(s) until your voltage goes down. So next:

• Probe the power side of same fuse.
• If volt drop falls to .09 volt, the resistance is between there and your last measurement (in this case, right there at the fuse itself)

That's as unlikely as it sounds, so if you measure the same 7 volt drop there, just take black probe way back and measure at the source:

• Probe between battery positive terminal (red lead) and the threaded positive terminal stud at solenoid relay (black lead)
• Still 8 volts?

Then your resistance is in that battery positive cable/terminals.

• At or under 0.20 volt?

Continue probing downstream.

Next probe battery power input at bulkhead connector, the big one in firewall that passes through and feeds fuse panel inside cab.

• Under .2 volt?
• Probe same wire at other side of connector inside cab.
• 7 volts?
• BINGO

Your resistance is in the connection between inner and outer bulkhead pass-through terminal(s). Dismantle and correct as necessary.

I'm not saying that this is where your problem is, because frankly I don't know. Furthermore, you might need to load the circuits up a little bit more to get accurate results, and turning on headlights should do that. Or extreme case scenario, crank the starter every measurement you take. Frankly though, if you're only getting five or six volts at the output side of the fuse with key on engine off, then your drop is going to show up key on engine off.

If my explanation is not too clear, Google "volt drop testing" and view whatever YouTube video explains it better than me.

Here is an example of volt-drop testing both positive and negative sides of a component individually.

View attachment 30499

(Leads are opposite my description, which would generate accurate, but negative values)

Whatever you choose, once you achieve successful results with this method, you will be hooked on volt drop testing forever, and the more you use it, the more you will come to see how simple it really is.

Oh, and it works on both legs, positive and negative sides. Jus hook DVOM black to battery negative and probe ground points with DVOM red, crank starter and check value.

If under .200 volt, you're done. You've confirmed ground integrity if every circuit between test point and battery. No more guesswork needed, no more removing and cleaning up grounds needed, that side is done, and all your grounds are good.

(The reason I focused on positive side to begin with is because you've already measured a pretty significant voltage loss that's your fuse)

Good luck.

Awesome reply Motech!
If I could add my 2cents.

Voltage loss testing is the most accurate and reliable method out there for certain! (As long as its understood, and performed correctly)
Motech's right up is 100% on point.
All I can add is that it appears that during the testing all of the fuses were removed.
The one main rule with voltage loss testing is that the circuit has to be completely connected and turned on for the results to help you. (Even if the circuit wont function.)
What I suggest is that you hook everything back up and focus on one circuit that doesn't work. Ignore the rest. (Bad grounds and high resistance have a way of making the vehicle look possessed)

Go the the light or device you are trying to repair and measure the voltage across it while plugged in. You should see battery voltage there. (It will likely show a very low voltage explaining why it doesn't work)
Next with everything still turned on, measure from B+ to the positive side of the load you are trying to fix. (This will show the voltage loss on the positive side as Motech pointed out.)
Repeat for the ground side. (Measure between the batt post and the neg side of the load)
If you find a voltage loss That equals the amount you were missing at the load, test that side of the circuit like Motech explained.
Always keep 1 meter lead on the battery and work back through the circuit until your big voltage loss number changes to a small number. At this point, your bad connection lives between the last big voltage and the first small voltage.(Again like Motech said)
You will need decent wiring diagrams to help you find connectors to measure at, but when done correctly, this method eliminates the possibility of a hard electrical problem.
Last thing, its really difficult to ignore all of the weirdness going on in the system because we are trained to look at everything, evaluate and look for commonalities help pinpoint the problem but with electrical gremlins, it can often be more confusing than good!
I promise, if you fix the root cause of one thing not working, all the rest will be repaired magically if they were related.
Hope that helps
Cheers

 

[Wishmeluck]

Just an update: Im working on putting everything back together and will continue testing this week. Thank you so much to everyone for all your help and will keep you posted.

 

[jdabnabe]

I wish I had Motech working for me when I was in the Army.

 

[Motech]

I wish I had Motech working for me when I was in the Army.

Now I'm blushing.

Funny thing is, so do I!

I often regret not enlisting and pursuing my training in the military. It's what my father did, a gearhead that enlisted in the USAF straight out of high school in 1963 to serve as an Air Force mechanic. Near 60 years later, he still imparts mechanical lessons through tales of what he learned there near 60 years ago!

Thank you for your compliment. Means a lot.

And what's the WO?

 

[Wishmeluck]

Update:

The alternator is completely unplugged right now so Im not sure if that had something to do with it. While tugging and pulling and finegaling wires around the dash I found four wires coming from what looks like a very elementry ECU that were broken off inside the connector. To repair it I used connectors from the old turn signal indicator in the column since the wire colors matched up. Then I decided to replaced the ignition switch on the column (not the cylinder, the other one with all the wires) cuz something was telling me it was glitchy and, well...it was cheap so why not just have it be new too lol.

Things started working out from there, albeit a little glitchy. After that I found a couple lingering grounds that were hiding in tucked away places on the dash frame that were pretty fugly so I cleaned them up, and a fuse slot that had some lingering corrosion I missed that was causing hiccups.

But....It all works flawlessly now .

Thank you all for your help and on to the next thing!!

 

[johnnyreb]

Update:

The alternator is completely unplugged right now so Im not sure if that had something to do with it. While tugging and pulling and finegaling wires around the dash I found four wires coming from what looks like a very elementry ECU that were broken off inside the connector. To repair it I used connectors from the old turn signal indicator in the column since the wire colors matched up. Then I decided to replaced the ignition switch on the column (not the cylinder, the other one with all the wires) cuz something was telling me it was glitchy and, well...it was cheap so why not just have it be new too lol.

Things started working out from there, albeit a little glitchy. After that I found a couple lingering grounds that were hiding in tucked away places on the dash frame that were pretty fugly so I cleaned them up, and a fuse slot that had some lingering corrosion I missed that was causing hiccups.

But....It all works flawlessly now .

Thank you all for your help and on to the next thing!!

Glad to hear you got your problem fixed.

 

[jdabnabe]

Now I'm blushing.

Funny thing is, so do I!

I often regret not enlisting and pursuing my training in the military. It's what my father did, a gearhead that enlisted in the USAF straight out of high school in 1963 to serve as an Air Force mechanic. Near 60 years later, he still imparts mechanical lessons through tales of what he learned there near 60 years ago!

Thank you for your compliment. Means a lot.

And what's the WO?

A WO is Warrant Officer. We sit in between the enlisted ranks but “below” the Commissioned Officer Ranks. You have to be enlisted first and have a minimum time in service and time in grade requirements. Each specialty is different. It gets more convoluted since a Chief Warrant Officer 2 is now a commissioned officer and a CW3 is a field grade. It was awesome because you are really not messed with.

 

[jdabnabe]

Update:

The alternator is completely unplugged right now so Im not sure if that had something to do with it. While tugging and pulling and finegaling wires around the dash I found four wires coming from what looks like a very elementry ECU that were broken off inside the connector. To repair it I used connectors from the old turn signal indicator in the column since the wire colors matched up. Then I decided to replaced the ignition switch on the column (not the cylinder, the other one with all the wires) cuz something was telling me it was glitchy and, well...it was cheap so why not just have it be new too lol.

Things started working out from there, albeit a little glitchy. After that I found a couple lingering grounds that were hiding in tucked away places on the dash frame that were pretty fugly so I cleaned them up, and a fuse slot that had some lingering corrosion I missed that was causing hiccups.

But....It all works flawlessly now .

Thank you all for your help and on to the next thing!!

Great job. Now you can enjoy it.

 

[johnnyreb]

Now I'm blushing.

Funny thing is, so do I!

I often regret not enlisting and pursuing my training in the military. It's what my father did, a gearhead that enlisted in the USAF straight out of high school in 1963 to serve as an Air Force mechanic. Near 60 years later, he still imparts mechanical lessons through tales of what he learned there near 60 years ago!

Thank you for your compliment. Means a lot.

And what's the WO?

Warrant Officer

 

[johnnyreb]

A WO is Warrant Officer. We sit in between the enlisted ranks but “below” the Commissioned Officer Ranks. You have to be enlisted first and have a minimum time in service and time in grade requirements. Each specialty is different. It gets more convoluted since a Chief Warrant Officer 2 is now a commissioned officer and a CW3 is a field grade. It was awesome because you are really not messed with.

Unless they messed will all the enlistened men and he was reported---then the wo was grass and the co was the lawn mower. Saw it happened in Germany and I was the enlisted man that reported the wo.

 

[jdabnabe]

Unless they messed will all the enlistened men and he was reported---then the wo was grass and the co was the lawn mower. Saw it happened in Germany and I was the enlisted man that reported the wo.

Then you had a bad Warrant. Plus things have changed. My CPT could tell me what to do but I was a Field Grade so there were things he knew that I didn’t have to. Mainly the BC would put out things for the Field Grades and I would default to the BC guidance. Plus there is now a Company Grade Officer Evaluation Form and a Field Grade Officer Evaluation Form. As a W3 you are rated on the Field Grade form. Mainly it really came to housing/accommodations and privileges. I would get Field Grade housing where a CPT would get Company Grade. I would get a higher allowance for hotel rooms and rental cars. I would get higher seating on aircraft. For instance, we chartered a 747 and I got 1st Class seating while my CPT sat in coach. I was authorized a rental car where my CPT was not. I was authorized to stay in a hotel while my CPT slept in the barracks. I was allowed to go off post and eat and drink while my CPT was not.

I only had two E9s and one E8 that I had to put in their place and only one was in my actual unit. The one in my unit was the S3 SGM and he had been a LEG Infantryman his entire career. I had been a Paratrooper on jump status for over 20 years, Master Rated Parachutist with well over 100 static line jumps. He didn’t understand the hierarchy of Airborne units so I explained to him that I had E4s with more jump experience than he had and therefore he was a Cherry and needed to realize that he was the FNG. My CSM, a guy that went from E1-E8(P) in the Ranger Regiment laughed. He didn’t like him either. He was a POG so…

 

[johnnyreb]

Then you had a bad Warrant. Plus things have changed. My CPT could tell me what to do but I was a Field Grade so there were things he knew that I didn’t have to. Mainly the BC would put out things for the Field Grades and I would default to the BC guidance. Plus there is now a Company Grade Officer Evaluation Form and a Field Grade Officer Evaluation Form. As a W3 you are rated on the Field Grade form. Mainly it really came to housing/accommodations and privileges. I would get Field Grade housing where a CPT would get Company Grade. I would get a higher allowance for hotel rooms and rental cars. I would get higher seating on aircraft. For instance, we chartered a 747 and I got 1st Class seating while my CPT sat in coach. I was authorized a rental car where my CPT was not. I was authorized to stay in a hotel while my CPT slept in the barracks. I was allowed to go off post and eat and drink while my CPT was not.

I only had two E9s and one E8 that I had to put in their place and only one was in my actual unit. The one in my unit was the S3 SGM and he had been a LEG Infantryman his entire career. I had been a Paratrooper on jump status for over 20 years, Master Rated Parachutist with well over 100 static line jumps. He didn’t understand the hierarchy of Airborne units so I explained to him that I had E4s with more jump experience than he had and therefore he was a Cherry and needed to realize that he was the FNG. My CSM, a guy that went from E1-E8(P) in the Ranger Regiment laughed. He didn’t like him either. He was a POG so…

FNG-HAHAHAHA-I know where you been. You sound like a #1 papa saun. Thank you for serving our country and welcome back home. Yes the wo in Germany was a pain to everyone---the one I had in Texas was a great guy. Mr Gobson was his name in Texas. Don,t remember the sob in Germany--everyone had a different name for him and it wasn,t good.

 

[jdabnabe]

FNG-HAHAHAHA-I know where you been. You sound like a #1 papa saun. Thank you for serving our country and welcome back home. Yes the wo in Germany was a pain to everyone---the one I had in Texas was a great guy. Mr Gobson was his name in Texas. Don,t remember the sob in Germany--everyone had a different name for him and it wasn,t good.

As a Warrant, I hated Warrants that were a pain in the ass. Usually those guys are also not well liked amongst the other Warrants. I found that if the Warrant was a senior SSG or SFC when selected then they were great guys. If selected at E5 or junior E6 or an E8 then they were pretty bad. Every bad Warrant that I knew fell into those categories. I know of two that remanded back to their previous enlisted ranks. They NCOs had a field day with them…

 

[wyo58]

Update:

The alternator is completely unplugged right now so Im not sure if that had something to do with it. While tugging and pulling and finegaling wires around the dash I found four wires coming from what looks like a very elementry ECU that were broken off inside the connector. To repair it I used connectors from the old turn signal indicator in the column since the wire colors matched up. Then I decided to replaced the ignition switch on the column (not the cylinder, the other one with all the wires) cuz something was telling me it was glitchy and, well...it was cheap so why not just have it be new too lol.

Things started working out from there, albeit a little glitchy. After that I found a couple lingering grounds that were hiding in tucked away places on the dash frame that were pretty fugly so I cleaned them up, and a fuse slot that had some lingering corrosion I missed that was causing hiccups.

But....It all works flawlessly now .

Thank you all for your help and on to the next thing!!

Good for you! now you know a bunch more about it than most people ever will! Electrical is usually something logical went wrong, I believe you got it licked now. And future problems if they occur you will be a step ahead of them!