New fuse block melting!! Fuse #7

[Mike C.]

Sigh... took the car out yesterday and smelled a burning smell. Decided to fire the car up again today, took it around the block, and smelled it again. Pulled the lid to the relay compartment, and sure as hell, fuse #7 didn't pop... it's freaking smoking. The top of my nice, new fuse box is melted.

Soooo, start throwing ideas. Any ideas. Noted last week FV is NOT buzzing anymore (started checking why i was getting such crappy fuel economy... ), have a spare here that I was going to plug in to check the part.


A little more background: Noticed #7 was starting to melt last year when the fuel pump died. Since then it's been replaced with a new unit.


*updated with pics. Sorry about the quality, it's pouring rain and im rushing to get the damn thing to focus.*

http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0804.jpg
http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0803.jpg
http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0802.jpg

[denis45700]

Specialty auto sells these
http://i986.photobucket.com/albums/ae347/mike45700_0/Delorean/0f3e1fbc.jpg
Fuse extenders. #7 is the
*main one that melts in the
*fuse block.* $4.50 ea.
Add to Basket
Save the fuse block,
*Made*to length, but I would
*keep the wire*as long as
*possible makes a good*heat
*sink. Black wire holder
*10*amps or less, orange wire *holder 10*amps up. crimped, *soldered and*shrink tubing,

[David T]

Stating the obvious, you have to find out why you are drawing so much current in that circuit. Usually a sign of a fuel pump going bad. Could also be a problem in the Control Pressure Regulator. Make sure all connections are clean and tight in the fuel pump circuit. There is a plug in the harness up inside where the bucket is for the W/W reservoir. Make sure you have an Inertia switch with a white splotch of paint and it is on the side of the footwell, not on the Lamnda counter. Try disconnecting the CPR and you can also look inside and see if it is burnt up.
David Teitelbaum

[Delorean Industries]

Almost as bad as installing a hot start relay. This is just masking the underlying problem. Definitely get to the bottom of why the number 7 circuit is being excessively overloaded. Check out the fuel pump circuit here: http://dmctalk.org/showthread.php?40-All-Wiring-Schematics on the diagrams. That is where I would start looking for issues.


Specialty auto sells these
http://i986.photobucket.com/albums/ae347/mike45700_0/Delorean/0f3e1fbc.jpg
Fuse extenders. #7 is the
*main one that melts in the
*fuse block.* $4.50 ea.
Add to Basket
Save the fuse block,
*Made*to length, but I would
*keep the wire*as long as
*possible makes a good*heat
*sink. Black wire holder
*10*amps or less, orange wire *holder 10*amps up. crimped, *soldered and*shrink tubing,

[Totally 80s]

Seems like number 7 has poor engineering problems. Even specialt's site says this is the one that melts.
Perhaps we need a real fix to this engineering problem rather than just "clean the grounds" approach is in order.

[denis45700]

Almost as bad as installing a hot start relay. This is just masking the underlying problem. Definitely get to the bottom of why the number 7 circuit is being excessively overloaded. Check out the fuel pump circuit here: http://dmctalk.org/showthread.php?40-All-Wiring-Schematics on the diagrams. That is where I would start looking for issues.

Obviously this is not a permanent solution. But it will keep the fuse box from melting while you figure out the high amp draw.

[Delorean Industries]

Obviously this is not a permanent solution. But it will keep the fuse box from melting while you figure out the high amp draw.

Exactly. But it is marketed to be permanent.

[Mike C.]

Dropped the washer bottle, and went for that harness location first since I hadn't been in there. Surprisingly, connectors were in amazing condition and look brand new.

http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0809.jpg
http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0812.jpg


No sign of corrosion or burns at all. Leaving bottle out for now because i need to replace the washer motor.





One thing though, anyone ever seen this before? Tied into black/purple and white/purple with red vamp clips.

http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0807.jpg
http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0806.jpg


Heading into engine bay now. When checking cpr, noticed corrosion on one of the pins. Taking a wire brush and jeweler's file to clean it up now.

[Mike C.]

Went back into relay compartment and pulled up the fuseblock. l wanted to make sure I had a secure connection to the fuse clips, and sure enough I did. Pulled the lambda relay and all the sockets up, checked underneath for any signs of melted wiring, arc-ing, etc. All relay clips are in place, no signs of arc-ing.

While cleaning the corroded prong on the CPR, I noticed the other prong is VERY weak and bent with almost no force, so I gently put it back into place. I have a spare CPR sitting here and may just install that in the meantime.

[Michael]

One thing though, anyone ever seen this before? Tied into black/purple and white/purple with red vamp clips.

http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0807.jpg
http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0806.jpg

Definately a capacitor, but why it's there I have no idea. I do not like those connectors though, they are nothing but trouble and unreliable as heck(the wings-a-loft door launcher kit is full of those).
The only thing I can think of is in the old days, people would put a capacitor on anything to supress noise in the stereo speakers. Fuel pumps, alternators, etc.

[Chris Burns]

Ah, lucky number 7. This problem reminds of a problem my BMW 320i had. The fuel pump fuse kept frying and at the time we couldn't figure it out. My car used the same K-Jet system as a Delorean.

How hard is it to replace a CPR?

[Ozzie]

Mike,
Check the harness section that plugs into the the fuel pump's wiring extension. I found about 3" of very brittle and wiring insulation, at the harness section which was just under the body, and wound up replacing about a 6" of that wiring.

Here ya go, I did a quick photo recap:
http://dmctalk.org/attachment.php?attachmentid=8780&d=1330904845

[Bitsyncmaster]

Pull the bottom plate off your CPR and look at the wiring. My bet is the that wiring is toasted

[Mike C.]

Dave, Will be pulling the CPR tomorrow and will pull it apart once it's here.

As for that spliced in capacitor thing, apparently that white/purple wire goes to the fuel pump (!) and the black/purple goes to the seat belt switch (? See C-6 in the color wiring diagram PDF). Can anyone think of why someone would have wired that in?!?


Ozzie, Will definitely check that. I hope it's just the same thing. Hopefully one of these 3 things will fix it.

[David T]

Those connectors are garbage. They have a steel blade that cuts into the wire when you squeeze it. The steel blade rusts and where it pierces the insulation it allows moisture into the wire. They are meant to be fast and cheap. The cap was probably installed during a radio upgrade to suppress electrical noise. I would remove them and the cap and neatly tape the wires. If the problem isn't the pump it is probably the CPR. This is assuming you used nice, shiny, new connectors in the fuseblock for #7 and they gripped the fuse tightly.
David Teitelbaum

[WelmoedJ]

Some people like those things as they are easier than doing it the right way (solder).

The steel blade not only cuts into the wire, but it most of the time also cuts some or more strands.
That's fatal to any electrical circuit.

I have been correcting the use of those splice connectors (vamp clips as you call them) many a time by renewing sections of wiring as the clip had cut almost all but some three strands.
Don't have to explain, I assume, what that means in continuity in that circuit.

[Ron]

As for that spliced in capacitor thing, apparently that white/purple wire goes to the fuel pump (!) and the black/purple goes to the seat belt switch (? See C-6 in the color wiring diagram PDF). Can anyone think of why someone would have wired that in?!?
$.02
Black/Purple is also the color of the other fuel pump wire... as said, the cap was probably installed for radio noise suppression.

The melted spots on those fuse blades are caused by high resistance at those points, simply a bad connection, new or not. Something in the circuit may have been drawing too much current and the resulting heat could of eased the tension on the clips (starting a vicious circle) -- Monitor the amp draw...If its OK, the clips are crappy or ya bent them...

[Bitsyncmaster]

I don't think there is any way a new fuse block has bad connections unless the fuse was not fully seated. I still think you have a high current load. A 20 amp fuse will take about 25 amps of current to blow.

My WUR had blown those heater wires to an open circuit and still did not blow the fuse. That is why I fused the WUR with a 3 amp fuse.

[David T]

A 20 A fuse will overheat if you ask it to pass more than 75% of 20 A or 15 A continuously. Good practice requires enough overrating to prevent this. A sudden spike over 20 A will, of course, cause the fuse to blow quickly. Also realize the fuse is there to protect the wiring, NOT the devices connected. One of the reasons circuit # 7 is so notorious is because it is one of the "continuous" circuits, ie, it is always drawing full current while the car is in operation. Most circuits in a car are intermittent. That gives everything a cycling period in which to cool off a little. This is called "duty cycle" and is one of the "tricks" used in the cooling fan circuit during A/C operation.
David Teitelbaum

[Totally 80s]

A 20 A fuse will overheat if you ask it to pass more than 75% of 20 A or 15 A continuously. Good practice requires enough overrating to prevent this. A sudden spike over 20 A will, of course, cause the fuse to blow quickly. Also realize the fuse is there to protect the wiring, NOT the devices connected. One of the reasons circuit # 7 is so notorious is because it is one of the "continuous" circuits, ie, it is always drawing full current while the car is in operation. Most circuits in a car are intermittent. That gives everything a cycling period in which to cool off a little. This is called "duty cycle" and is one of the "tricks" used in the cooling fan circuit during A/C operation.
David Teitelbaum

Fkn Deloreans!:mad1:

[David T]

This is not unique to Deloreans. It is rather common among British cars generally. Lucas undersized and overrated the electrical systems in all of the cars they were used in. It was even worse in earlier British cars, what we have now is an "improvement"? On early Jags they only had 4 glass fuses for the whole car! Fabric covered wire, steel nuts and bolts for connectors, no waterproof plugs, etc. There is a reason Lucas earned the nickname "Prince of Darkness". The company motto is "Get Home Before Dark". At least all of the problems are well documented and we have good, tested fixes. It DOES take some preventive maintenance to keep the electrical system working as it should. It can't be ignored and should be inspected regularly.
David Teitelbaum

[congerz83]

Those connectors are garbage. They have a steel blade that cuts into the wire when you squeeze it. The steel blade rusts and where it pierces the insulation it allows moisture into the wire. They are meant to be fast and cheap.

David is 100% correct about these connectors. I call them "scotch-locks". To be brief, they totally suck. I used them a little while ago on the off-road lights on my Grand Cherokee. For the next two weeks I was chasing connection problems almost daily. I recently soldered the connections, and I wish I had did it from the beginning, as there has not been a problem since.

Observe...
http://i135.photobucket.com/albums/q152/congerz83/Jeep%20stuff/Off-RoadLights.jpg

[DMC5180]

When I replaced my fuse box many years. back I made sure that the Wire going into the the terminals Fresh and not heat stressed from previous corrosion and resistance build up. I replaced about 9 inches of wire on each leg with clean stuff. Its been cool as a cucumber ever since.

[Mike C.]

UPDATE:

I've totally ignored the car. She made it home, parked it, concentrated on packing, sorting, moving plans, etc...

Since Celebration is this weekend, I figured what the hell and decided to work on the car today. I replaced the CPR with one i had purchased from Adam (AdmiralSenn) a few yrs back, cut out my "They feel tight, but feel a little loose" fuel pump disconnects, and fired the car up.

The car sputtered to life after a few cranks...why? The fuel pump wasn't running. Weird. Smacked #7 fuse, and magically I heard the pump start to prime. Cranked for a couple of secs, let the car settle, and she fired right up like a champ. Oddly enough, I could now adjust my air/fuel mixture with the new CPR and was able to lean down my overly rich motor. Seriously, I turned it down a couple of turns it was THAT rich!

Car is idling like a champ. Went to the fuse block and touched #7 after 2 minutes of the car running... HOT. flicked it, and it smoked! Well fuck a duck! Decided to pull out the fuse and cut the wires to #7. I ran over to autozone and wired in a remote fuse holder to test to see if it was just the clips. Sure as hell, car fired right up, ran outside for just under an hour, and the fuse is ICE cold. the connectors are cold, the wires are cold. I hate having a crappy looking jumper in there, but when I get to Orlando, I will properly extend the wires and tuck it in neatly so it looks presentable. I am going to smooth in the melted section of the fuse box. I hate doing that because the damn thing was only 2 yrs old, but what can you do? it's one of those unpredictable things. At least I didnt lose the car over it.

So, in all this, I had a bad CPR, a bad clip on my fuse, and a car that was running super rich.

Took her for a spin, and SHE'S ALIIIIIIIIIIIVE! Runs like a champ again. Tomorrow will be another 240 mile trip to Orlando to Brandon's house where I will make her pretty again for the show. I failed at taking pics the last couple of years and want to get as many member photos as possible as this may be my last year at Celebration until I am done with clinicals and labs, or i sell the car.

Thank you ALL for the great advice.

Thanks Adam for the CPR!

[AdmiralSenn]

No problem. Just another example of Christine being idiotic for her own sake... like I said on Sunday, all of those parts work for other people, just not on my car.

[lazabby]

Our cars have an amazing ability to protect fuses from blowing while blowing everything else up. This photo shows a fuse that was nearly melted in my car but it still didn't blow.

[David T]

Everyone should check to be sure you have the correct size fuse in each of the spots. It is all too common for someone (we can blame the DPO(Dreaded Previous Owner) ) for sticking in whatever size was handy when the last one blew and now we just keep replacing withe the same, incorrect size. It is also important to regularly check the fuseblock and relays for signs of overheating. We all know the wiring in the car is marginal so it requires regular attention. Do NOT put the cover on the fuseblock. It traps heat and just makes the whole situation worse. Keep it nearby with a supply of extra fuses of various sizes and a couple of jumpers. Very bad for a fuse to continuously handle more than 75% of it's rated capacity. At higher ambient temperatures that derating is even greater than 25%.
David Teitelbaum

[Chris 16409]

So I discovered one of the wires feeding fues #7 had burned and cut off power to the fuel pump. For some reason (only the good people at Lucas know) one of the brown wires is a smaller gauge than the other. The thinner wire was the one that got singed. I never had a fues melt, but I'm guessing the crimp connection on that wire must have been subpar. I think I will run a new updated wire but need to know how to remove the old fuse socket and add a new one. For now I'm running an inline fues holder. I remember James was saying if you call in you can buy indiviual fues terminals.

[Bitsyncmaster]

Those terminals are really hard to remove. If your block melted, you will also find it impossible to remove without damage. I'm assuming you have the OEM block. When I replaced my fuse block, I just cut the wires off near the crimp rather than remove them like the instructions stated.

[Chris 16409]

Those terminals are really hard to remove. If your block melted, you will also find it impossible to remove without damage. I'm assuming you have the OEM block. When I replaced my fuse block, I just cut the wires off near the crimp rather than remove them like the instructions stated.

Hey Dave, looking at the service records provided to me by the previous owner, I see that DMC-CA replaced the fuss box several years ago. The part was order from DMC-H. I'm not sure if it was a reproduction block as it has the manufacturer name on it (starts with a "P"). I'm guessing it did come with the improved terminals. Anyway. The block didn't melt, only the one wire got singed on the underside. What I'm going to do I run a hole new wire from the Lambda relay socket and solder it so only one wire is going to that particular relay terminal. I'm guessing they had to use a smaller gauge wire for one of the brown wires at the terminal because, two larger gauge wires would not fit in the terminal.

[DMC5180]

Chris,

When DMCH first started offering Replacement fuse boxes, they did so originally by cutting them off of Main Harnesses. They shipped out NOS (PRESSAC) take-off fuse boxes with NEW TERMINALS and OLD NOS FUSES that were originally in them. This only lasted about a year before DMCH realized there was enough demand to warrant having Fuse boxes reproduced. All NEW fuse box replacements are UNMARKED. They one of the rare remanufactured parts that don't say Delorean.com, which is a tell tale of a DMCH remanufactured part.

[Bitsyncmaster]

Hey Dave, looking at the service records provided to me by the previous owner, I see that DMC-CA replaced the fuss box several years ago. The part was order from DMC-H. I'm not sure if it was a reproduction block as it has the manufacturer name on it (starts with a "P"). I'm guessing it did come with the improved terminals. Anyway. The block didn't melt, only the one wire got singed on the underside. What I'm going to do I run a hole new wire from the Lambda relay socket and solder it so only one wire is going to that particular relay terminal. I'm guessing they had to use a smaller gauge wire for one of the brown wires at the terminal because, two larger gauge wires would not fit in the terminal.

Yes those double wire crimps required the use of smaller gauge wire. I do seem to remember that smaller gauge wire on the pump fuse. When I did my new fuse block, every double wire on the fuse pins was changed to one wire and spliced with a butt terminal in the harness. I've been finding many bad connections with double wire crimps even though the crimps look good. I'm thinking of selling a new relay ground harness (it's that bad). Maybe if you can get an highly active flux and solder those double wire crimps it may fix it. The problem is the wire is not tin plated and corrodes over time.

[Chris 16409]

Those terminals are really hard to remove.

If I can't remove the #7 fuse terminals, then I'll just solder in an inline fuse. I'm not going to put in a new block for just one bad fuse terminal. I believe the wire got singed because it was underrated and the crimp wasn't very good. Before I had the failure I was running #7 through an inline fuse in the fuse block. I noticed the one blade connector on the inline fuse was turning brown. That connection was getting too got since the wire crimp was failing under the fuse block. Had I been running the fuse directly in the block, it probably would have melted.

[Chris 16409]

So I got my number 7 fuse fixed up. I ended up rewiring the Lambda relay socket at the same time. One of the brown wires on fuse #7 comes from the Lambda relay socket. This stock wire was too thin, so I cut it out and wired in some larger guage wire. Originally, the lamba relay had 2 brown wires crimped to a single terminal (pin). I decided to use one large guage wire on its own terminal and soldered the brown wires to that. I used 14 AWG from the lambda relay to fuse #7.

[Silkie]

Sigh... took the car out yesterday and smelled a burning smell. Decided to fire the car up again today, took it around the block, and smelled it again. Pulled the lid to the relay compartment, and sure as hell, fuse #7 didn't pop... it's freaking smoking. The top of my nice, new fuse box is melted.

Soooo, start throwing ideas. Any ideas. Noted last week FV is NOT buzzing anymore (started checking why i was getting such crappy fuel economy... ), have a spare here that I was going to plug in to check the part.


A little more background: Noticed #7 was starting to melt last year when the fuel pump died. Since then it's been replaced with a new unit.


*updated with pics. Sorry about the quality, it's pouring rain and im rushing to get the damn thing to focus.*

http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0804.jpg
http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0803.jpg
http://img.photobucket.com/albums/v43/michael_cole/16336/Overheating%20Fuse%207%20on%2003-04-2012/IMAG0802.jpg


Your fuse, Is what my high beam fuse looks like.
My fuse box is melted too where the fuse goes.
When i noticed it. I pulled the fuse out!
And it's still out.

I just purchased my Delorean in August.
I did test all my lights and they work.
But i don't know if it melted on me?
Or the PO?

Any idea what caused this??

[WelmoedJ]

Your fuse, Is what my high beam fuse looks like.
My fuse box is melted too where the fuse goes.
When i noticed it. I pulled the fuse out!
And it's still out.

I just purchased my Delorean in August.
I did test all my lights and they work.
But i don't know if it melted on me?
Or the PO?

Any idea what caused this??

There can be a number of reasons causing wires to melt.
- Bitsyncmaster already pointed to bad grounds
- Pinched wires underneath the fuse box
- fuse sockets and fuses corroded (fumes from the battery under the relay compartment cause this corrosion * )
- crimp connection corrosion or bad crimp

*) Fumes from the battery compartment can get into the relay compartment.
Those fumes precipitate on the socket and fuse surfaces.
The precipitation looks kind of greyish and when sweeping one's finger over the fuse pins, the feeling is rubberish.
This layer prevents normal contact and causes heat build-up.
I found cleaning all fuse pins once every two years prevent the precipitation.

[blueguse]

So I got my number 7 fuse fixed up. I ended up rewiring the Lambda relay socket at the same time. One of the brown wires on fuse #7 comes from the Lambda relay socket. This stock wire was too thin, so I cut it out and wired in some larger guage wire. Originally, the lamba relay had 2 brown wires crimped to a single terminal (pin). I decided to use one large guage wire on its own terminal and soldered the brown wires to that. I used 14 AWG from the lambda relay to fuse #7.

I ran across this thread after someone shared this with me. Looks like what you did. I do worry about reusing the existing 18 AWG wire even if it's an inch, b/c it still would be a bottleneck.
72156

[Bitsyncmaster]

I ran across this thread after someone shared this with me. Looks like what you did. I do worry about reusing the existing 18 AWG wire even if it's an inch, b/c it still would be a bottleneck.
72156

Early on my ownership, I measured the wire strands and counted them and got a result that the small wiring on our car is equivalent to 19 AWG. It's a metric wire gauge.

[blueguse]

I ran across this thread after someone shared this with me. Looks like what you did. I do worry about reusing the existing 18 AWG wire even if it's an inch, b/c it still would be a bottleneck.
72156

I was incorrect, you would replace the wire from the fuse with a 14 AWG then splice in the existing RPM Relay and the Lambda wire. Removing the RPM Relay wire from the Lambda Relay.

721587215972160