The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

  • Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;) It will also allow you to view images in threads.

Please Support Southbay Fuel Injectors
Please Support VR-Speed Factory

2G Voltage drop

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
So I'm a little stumped.
My 2g gst blows the 60amp fuse from B+ in the engine fuse box at key on. This is what I know about that fuse:
Once power is through the main 60amp fusable link from b+ to the white and black wire, power is provided to the dedicated fuse number 8 and 11 in the engine bay fuse box aswell as 1, 5, 6, 10, and 11 in the multiuse fuse box in the interior. Only.
And if the 60amp fuse in the engine bay is blowing at key on, and none of those other fuses are blowing, then I should have a short between those fuses, and the 60amp fuse.
But there isn't a short. Zero wire damage or disconnections.

Is there anything else that could cause this fuse to blow at key on?

Photos are from the electrical service manual with little red dots to follow along where the points of interest are.

edit: later in time I discovered that replacing the 60amp fuse was allowing the problem to essentially "reset" but the fuse itself wasn't actually blowing. The true issue was voltage drop. This is explained later in the thread.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
 
Last edited:

dustyboner

DSM Wiseman
1,395
640
Mar 13, 2016
abq, New_Mexico
i guess you could try unplugging B-74 and dedicated fuses 8 and 11 then see if it still blows. if it does, check the wires where they go into the bottom of the engine fusebox. If it doesn't try each one individually, so put #8 in, try the key, if it doesn't blow, remove #8 and try with #11 and then B-74. Hopefully you'll be able to isolate where the problem is that way
You must be logged in to view this image or video.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
Obviously my problem is a short but with that, what would cause the 60amp B+ fusable link to blow without blowing any other fuses and only when the key is switched to on?

The wire that connects the 60amp fuse to the interior junction box shows zero continuity to ground. I have found no grounds there. It is simply a point a to point b wire providing power to the junction box as well as 2 other fuses in the engine bay fuse box. No other fuses are blowing.

According to both practice and the circuit diagrams there is nothing directly connecting this fuse to the ignition switch without another fuse inline. And no other fuses are blowing. Everything that I can find points to the single point a to point b wire having a ground but I have even disconnected it on both sides, ran a temporary wire, and tried to turn the key and it still blows the fuse.

Edit: my current step is disconnecting everything that fuse powers and disconnecting everything from the junction box to see if it still blows. I feel like the junction box is causing the issue but I have never heard of this failing.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
i guess you could try unplugging B-74 and dedicated fuses 8 and 11 then see if it still blows. if it does, check the wires where they go into the bottom of the engine fusebox. If it doesn't try each one individually, so put #8 in, try the key, if it doesn't blow, remove #8 and try with #11 and then B-74. Hopefully you'll be able to isolate where the problem is that way
So I am back at this issue. Thought I figured it out and I didn't. I have been working though this now again for 2 weeks. I can no longer ignore it LOL.

As it stands right now, with key off, I show no continuity to ground at the fuse. Zero continuity to ground at b-74. Zero continuity to ground at multipurpose fuses 1, 5, 6, 10, and 11. No continuity to ground at dedicated fuses 8 and 11.

With key on, all is the same with the exception of continuity to ground at the interior fuse box multipurpose fuses 1, 5, 6, 10, and 11. I was only able to get it to show this ground a hand full of times. At this point, with nothing else moved or changed since, I cannot get it to show again. But I know the problem is still there and didn't fix itself.

B74 has been disconnected aswell as dedicated fuses 8 and 11 and I will report back what happens.
 

luv2rallye

DSM Wiseman
7,971
841
Jun 7, 2003
Minneapolis, Minnesota
With battery disconnected unbolt the engine fusebox and turn it over and look at the wires underneath. I've seen a wire chaffed with it's insulation wore off in a spot that was touching another similar wire or ground. It was so close that it was intermittent with vibration. If necessary, re-connect the battery, key on, and move the wires around to see effect - just be careful when you do this.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
Now, I'm going to be alot more specific now as I just discovered this myself. This whole time I have been saying the 60amp fuse is blowing. But it doesn't blow necessarily. Hear me out.
I turn the key, everything powers up, and then almost powers down. The dash lights start to pulse dimly like a heart beat. The radio won't power up for longer then a second. Check engine light eliminates but I can't get ecmlink to connect to tell me what is happening. From that point forward. Turning the key just makes everything dim again without an attempt to power up.
Then i change the 60amp fuse. This get everything to try and fully power up again. Then back to dim and pulsing.
The fuse doesn't completely blow as I just discovered. Byt replacing the fuse creates the beginning part of the issue. Know what I mean?
I feel as though their might be something creating a massive voltage drop.

A while back when this first started happening, I got 12v ish at the fuse with the key off and almost 8v with the key on. At the time I thought that was the symptom of a short but now I don't know.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
With battery disconnected unbolt the engine fusebox and turn it over and look at the wires underneath. I've seen a wire chaffed with it's insulation wore off in a spot that was touching another similar wire or ground. It was so close that it was intermittent with vibration. If necessary, re-connect the battery, key on, and move the wires around to see effect - just be careful when you do this.
I actually did this yesterday. In these 2 weeks I have fixed a few broken wires under the bottom plastic if the fuse box. It didn't fix the issue but it was still good to find.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
I'm going through connecting one thing at a type looking for any changes and I found something.
As soon as I connect the the plug supplying power from fusable link number 6 and turn the key to ignition on, I see a massive voltage drop. Key off im measuring 12.6v and key on im measuring 8.2v.
Any suggestions are good suggestions.
 

luv2rallye

DSM Wiseman
7,971
841
Jun 7, 2003
Minneapolis, Minnesota
So now you're saying it's the 30A fusible link #6 (and not the 30A "defogger" fuse #6 which comes from the 60A fuse)? Before you were saying it's the 60A fuse which is on a completely different path from the battery!

The 30A "Ign sw" fusible link #6 comes directly from the battery and goes to the ignition switch which powers dozens of things. I'd start by removing every fuse in the inside fuse box to see if problem goes away. If so, start replacing them one at a time. If it doesn't go away also unplug the alternator and remove all other engine fuses too.

If still stuck read this: https://www.dsmtuners.com/threads/f...l-short-or-battery-drain.179481/#post-1496998
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
So now you're saying it's the 30A fusible link #6 (and not the 30A "defogger" fuse #6 which comes from the 60A fuse)? Before you were saying it's the 60A fuse which is on a completely different path from the battery!

The 30A "Ign sw" fusible link #6 comes directly from the battery and goes to the ignition switch which powers dozens of things. I'd start by removing every fuse in the inside fuse box to see if problem goes away. If so, start replacing them one at a time. If it doesn't go away also unplug the alternator and remove all other engine fuses too.

If still stuck read this: https://www.dsmtuners.com/threads/f...l-short-or-battery-drain.179481/#post-1496998
Yeah the 60amp main power fuse came into question because changing it allows me to recreate the problem. I do not know why.
The fusable link number 6 in the engine bay fuse box for the ignition switch is now in question. It has an 8 gauge white wire that goes from it to the driver side fender. With that wire being the only thing connected (all other connections disconnected and fuses removed) and turning the key creates a voltage drop.
This goes to alot of stuff. Digging through the electrical service manual shows quite literally too much stuff to list powered by that circuit.
A short would blow fuses but I'm seeing voltage drop. What causes that?
 

luv2rallye

DSM Wiseman
7,971
841
Jun 7, 2003
Minneapolis, Minnesota
That 8 gauge (as you call it - it's actually 3 square mm which is closer to 12 AWG) white wire goes ONLY to the ignition switch and a 20A fuse #17 for a sunroof. So pull every fuse you see first to see effect.

A voltage drop w/o fuse blowing is a partial short (or too many loads on the circuit). A partial short may be either a wire shorting or a device shorting out internally.

If you're really desperate and suspect a short in a wire loom but don't know where, here's an old technique using a circuit breaker and compass to find it: https://www.dsmtuners.com/threads/taillight-fuse-keeps-blowing.219712/#post-1841697.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
A few recommendations I got on Facebook that I'm going to try today is leaving the ignition circuit connected and disconnecting the mpi relay to see if the voltage drop goes away. Another recommendation was to disconnect the starter as the starter should be the only thing able to draw that much power.
Putting those recommendations here as Facebook disappears and here stays forever.
 

luv2rallye

DSM Wiseman
7,971
841
Jun 7, 2003
Minneapolis, Minnesota
Yes, disconnect everything you can (starting with all fuses everywhere) until the drop disappears (or literally disconnect everything in the car and start adding them back in one at a time until the drop re-appears). If there's a short/partial short, anything can draw that much power (and may burn up wires so be careful). Sometimes if burning up wires is a real possibility, I'll put a tail light bulb in series with the battery + terminal to limit current flow. It drops voltage so voltage at all other places will be less than normal. However you can then start testing voltages at suspected places to see if there's voltage where there shouldn't be (due to a short/partial short which is completing a circuit allowing current to flow there). Measuring voltage is ALWAYS better, easier, and more reliable than measuring resistance (plus resistance can completely change on non-linear devices fooling you).
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
Yes, disconnect everything you can (starting with all fuses everywhere) until the drop disappears (or literally disconnect everything in the car and start adding them back in one at a time until the drop re-appears). If there's a short/partial short, anything can draw that much power (and may burn up wires so be careful). Sometimes if burning up wires is a real possibility, I'll put a tail light bulb in series with the battery + terminal to limit current flow. It drops voltage so voltage at all other places will be less than normal. However you can then start testing voltages at suspected places to see if there's voltage where there shouldn't be (due to a short/partial short which is completing a circuit allowing current to flow there). Measuring voltage is ALWAYS better, easier, and more reliable than measuring resistance (plus resistance can completely change on non-linear devices fooling you).
I just want to clarify one thing with you. As I meantioned yesterday, I had discovered the voltage drop when I connected the 3mm square wire from fusable link number 6 that supplies power to the ignition switch and fuse number 17 to the sunroof. You had said it supplies only these.
So I should be looking for something that supplies power from the ignition switch correct?
So looking at the electrical service manual, I should be looking for everything powered by "ON" (when I notice the problem).
Pictures of what pages in looking at are attached.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
 

luv2rallye

DSM Wiseman
7,971
841
Jun 7, 2003
Minneapolis, Minnesota
Yes. And there's a LOT of things powered by the ignition switch (as the diagrams indicate) so it may take awhile. Most have another fuse on them which is why you should remove all fuses first to see if problem goes away. If it does, start replacing fuses one at a time to find the problem circuit. If it doesn't go away, you may have a short before it gets to the fuse (or someone put in too large a fuse and the device itself has a partial short - and good idea to check if proper fuses are there now). Wiggling wires in suspected areas also sometimes helps in finding shorts (they may appear/disappear).
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
Okay. "Interior relay box dedicated fuse number 13" for the mirror control. Anyone know where that's at?
It isn't the engine bay fuse box as it only has up to 12 fuses.
It isn't the interor multipurpose fuse box because MPF 13 goes to ABS, A/C switch, auto compressor, blower motor, and the defogger relay.
Photo attached. This is the last thing I need to disconnect to test. Besides the "generator relay" which turns out isn't even a relay so I just unplugged the alternator.
You must be logged in to view this image or video.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
Never mind. I have isolated the circuit. With this attached list and everything disconnected fuse wise I no longer get a voltage drop at key on. I'm now going to connect one at a time alone untill I get the drop to isolate which circuit it is
You must be logged in to view this image or video.
 

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
In case you're still wondering, this fuse is high up under the driver's side
So I've damn near reconnected everything and I now can't get the voltage to drop at all.
Sevearly confused.
I'm not going to argue about the problem just "going away" but a problem like this doesn't just disappear...
 

ShadyDoins

Proven Member
94
35
Nov 5, 2007
Northampton, Pennsylvania
First of all I just want to say this is probably the best thread I have seen in 10 years. This is high level knowledge in this thread. Fantastic. So first observation is that you don't have a voltage drop. Voltage drop would not effect the whole car unless it was at the battery terminal. Do you have a ground from the battery to the engine and one to the body? Also does the problem only happen on key on but then goes away after a certain amount of time and then everything is normal?

Or if you start the car does the problem go away. If you can't start it jump the car and see what happens, it's possible you just have a bad battery and when you key on the load makes the voltage dip but not because anything is actually wrong
 
Last edited:

95FullSend99

Proven Member
377
188
Dec 3, 2019
ledyard, Connecticut
First of all I just want to say this is probably the best thread I have seen in 10 years. This is high level knowledge in this thread. Fantastic. So first observation is that you don't have a voltage drop. Voltage drop would not effect the whole car unless it was at the battery terminal. Do you have a ground from the battery to the engine and one to the body? Also does the problem only happen on key on but then goes away after a certain amount of time and then everything is normal?

Or if you start the car does the problem go away. If you can't start it jump the car and see what happens, it's possible you just have a bad battery and when you key on the load makes the voltage dip but not because anything is actually wrong
#BeingBackForums
So it does effect the entire car. In my initial realization of a problem, I had zero understanding of how electricity works. This has been a big learning curve for me. With that, when this first happened as well as the discovery of it still happening in recent weeks, I noticed that everything in the car starts to start up and then gets dim and sort of pulses. All lights, the gauge cluster, radio doesn't start, and the ecu doesn't have enough power to connect to ecmlink to see what is going on at the ecu.
Initially I took this as a short or maybe a fuse about to blow or something.
Everytime I went to the key "on" position it would go straight to dim and pulsing.
I noticed off a whim and random change of a fuse that changing the main 60amp fuse allowed the problem to essentially "reset" and try to power all the way on again. This is what lead to my confusion and misdirection towards a faulty 60amp fuse. At this point in diagnosis, I had only tested voltage one time and picked up 8ish volts and didn't think twice about it.
I tested for voltage once again a few days ago and at that point realized how big of an idiot I was being and changed the direction of this forum to "voltage drop". I had realized that the 60amp fuse may not have been the issue at all and that the drop was causing my issues.

As for grounds, the battery is in the trunk and I have a ground from the negative terminal to three spots. The rear sheet metal, the rear seat attachment bracket, and the passenger side front seat bracket. All grounds were bare metal upon attaching.

As for the engine, I have one from the cylinder head to the passenger frame rail, the bellhousing the frame rail, the starter to the bellhousing, the head to the intake manifold, the exhaust manifold to the head, the head to the firewall, the throttle body to the firewall, the motor mount to the driver side strut tower, the exhaust to the framerail, the alternator to the motor, and the alternator to the firewall.

The problem, as I learned yesterday, is intermediate. Most of the time it happens, sometimes it doesn't. But when it happens I have yet to find a way to get it to go away outside of blind chance. It happens no matter what and there is no time limit to wait for it to go away. At least not longer than the less then 5 min I'm allowing it to "pulse" before I decide that it's too high of a risk of damaging something to keep it going.

The car isn't to the point of starting. I'll need to be able to play around on ecmlink first to get it to start. This was winters build. The initial problem start midway through last summer. Before that, it was a running car. All it did was sit for a few months. Nothing electrical got changed other than a map sensor which isn't the problem.

I have a new battery in my basement though. I was going to wait to use it and keep using the old one untill I can get it started and idling as I didn't want to repeatedly drain a new battery during the new build initial start process.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com Raven Fabrication RixRacing RockAuto RTM Racing STM Tuned VR Speed Factory

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Top