Hi All. On my last road trip of the year (upstate NY) and noticed this contact seems to be melting (or already melted) in my 1975 GT4. Any ideas to keep it from getting worse? Reason to cut the trip short and go home to address or can I keep going for another two days!? thanks for the help Image Unavailable, Please Login Image Unavailable, Please Login
It's caused by a small resistance developing between the female spade terminal and the male spade terminal. At a minimum, unplug/replug the female spade terminal a few times to improve the connection. Ideally, you would clean the male spade terminal and "squeeze" the female terminal sides to have a tighter grip. Soldering all of the riveted connection is another way to improve the reliability of that style fuseblock.
Thanks Steve. Will give that a shot tomorrow before I head out. Any chance of something catastrophic happening or would I just lose my RH fan?
No, nothing too catastrophic, but it's a positive feedback situation -- a little unwanted resistance = some heating = oxidizes the connection more and weakens the metal = increases the resistance a little more = increases the heating more = even more oxidation, etc. Eventually, either the fuse will melt (not from the current being too high, but from this extra I^2*R heating at the connection being conducted by the metal into the fuse element), or the resistance will become so high that both fan motors will stop, or the plastic insulation over the terminal will catch on fire . Edit 1: Your problem may be a little self-inflicted. I checked the 308GT4 OMs, and that large red wire with the burned insulation is what brings in +12V power to all three fuses on the RH end of the fuseblock. The wire to the left of it in your photo (with the slightly bluish insulation) is something that someone added to go run something else; therefore, the total current on the burned up large red wire going thru that connection is higher than what it was designed for. Edit 2: You can also move the burned up female terminal over to the unused male terminal to the right just to have a fresher male terminal. (The top male terminals of those three fuses are all connected together by a plate on the backside of the fuseblock.)
Like Steve M said, get the soldering iron out and flow solder across each rivet to its copper bar. This should eliminate any fusebox issues for a long long time. To get this right, burnish the copper in the areas you intend to solder. A nice scuff up with 600 or 800 grit sandpaper will work. Clean those areas off with alcohol and go at it with the soldering iron and rosin core solder.
It can be heated to the point at which solder melts and not damage the fuseblock. There is no need to replace the fuse block if you can update the original with soldered connections. In my case I tightened each of the rivets BEFORE soldering them. But that was overkill. I did this 30 years ago and all is still fine.
I recently updated mine to a blade fuse type from a member here on fchat Turtlefarmer. It is far superior to the torpedo fuses.
So you wanna say that a torpedo fuse making contact on tiny points pressing on the flimsy copper tabs is as good as a blade fuse? Blade fuse has tighter and a solid contact. Blade fuses are more reliable and is a major reliability upgrade. Not to mention easier to find in a pinch. My original block melted in 2008 and left me stranded the one and only time in 20 yrs of ownership.
The problem with the torpedo fuse block has never been the contact between the fuse and the holder. It is always a problem with the rivets becoming loose. Soldering as I have shown solves that problem if done so before they are damaged making replacing them with more modern designs is superfluous. I soldered my OE blocks back in 2010 at the recommendation of my old tech who observed the fuel pump connection was running a little hot to the touch. Since soldering the problem has been solved. And it should be understood that just because the blade surface looks bigger doesn't mean the current path is. Current flow follows the path of least resistance and that is largely a function of the surface finish, as shown in the picture below where current only passes through the circled areas. Nothing wrong with updating if you so desire, but it really doesn't improve anything over soldering the OE blocks if they are in go0d shape. Image Unavailable, Please Login
The actual "fuse wire" is much smaller in diameter than the contact point of any type of fuse so having a larger external contact point does not add to the conductance capability. I agree that the solder method mentioned will do the job as well as any "upgraded" fuse block as far as electrical function is concerned. Of course, if you prefer the blade fuses because they are (usually) easier to remove/install and the value is MUCH easier to read(!), that's a different issue. But they are not "better" fuses as far as the circuit is concerned.
Hi John, thank you for the pictures of your soldering work of the fuse block. If I see it correctly, on the backside it's only necessary to solder the pairs which are connected by a metal plate – not the single ones which are riveted directly to the plastic plate. Is that correct, or should also the rivets of the single ones be soldered as well? Furthermore, on the second picture of the front, it looks like you have also soldered the corners where the actual fuse holder goes upwards in a right angle (see green circle). Is that also correct? If yes, I assume you have done this also on the upper part, not visible in the picture? Image Unavailable, Please Login Thank you for explaining! Robert
Yes, the back side is only soldered where there is a bridge between contacts to ensure good conduction through the rivet and across the bridge. The rivets that hold the bridges should also be soldered on the front side. Also on the front side as you can see, there are two male spade lugs on the lower row for each fuse. One is actually part of the fuse holder. The other is held in contact by the rivet. The soldering you have circled in green ensures good conductivity between the two spade lugs eliminating the reliance on the rivet pressure and removing the possibility of poor conduction due to oxidation between them. Anywhere there are two lugs coming off a fuse they should be soldered like that, upper and lower row. Hope that is clear. Image Unavailable, Please Login
Have to disagree that there isn’t an advantage to upgrading the fuse blocks from using torpedo style fuses to blade style. All (5) of my Porsche 911 used this torpedo style fuse and about every two years I would have to pull each of those fuses and clean each contact point.Made a hell of a difference. Should note that each one of these cars lived their life in a heated garage. The 308 use the exact same setup. Have owned (3) 308‘s and two of them were switched to Birdman fuse blocks. My current 308 has been running Sam’s fuse blocks for something like 6 years. Never another issue and have yet to routinely pull each fuse for maintenance.
Well, not to be a contrarian, but I've never had a problem with the actual fuses or fuse to holder contact in 36 years of owner ship. Never even touched the fuses or fuse block except to add a radio power wire when the car was new and the perform the soldering back in 2010. And the soldering wasn't a fuse problem, but a rivet problem. I did replace all the fuses when I soldered the blocks, just 'cause. Result may vary.
Thank you for the explanation and the elucidating picture, it is very clear now – even to a not very technical minded guy like me. I will try my best to do the modification without melting the whole fuse block.
