Lakeland Toyota?
MAD ammeter bypass question
- Thread starter 1MeanA
- Start date
-
'Cuda_ragtop
Woulda, Shoulda, 'Cuda!
Yessir. That's the one.
Dave999
Well-Known Member
ive always just run the standard ammeter
didn't work when i got the car
both leads on 1 stud and after testing i discovered it was shorted from the other stud to earth
it was removed from its position
the point where the studs pass through the metal support was dismantled
the old nylon and fibre washers that insulate the studs were thrown
new modern heat sink isolation collars and clear plastic/mica...(some odd stuff) used for insulating the earth tabs on power transistors was used either side of the plate, the thread of the studs was heat shrink wrapped to just past the metal plate, and the heat sink "Top Hat style" collars fitted from either side with a bit of smoothing and shortening, through the hole in the metal plate, thus insulating the studs from it in the same way as the original nylon did
i now have 3 layers of modern fire retardant insulation between the studs/nuts and the body of the ammeter/pod
the cable nuts are lock tight-ed and there is a spiky washer either side of the eye of the leads.
its been ok for 20 years... it might not be ok in the future but i feel i did a reasonable job of dealing with the usual problem.
Problem:-
Ammeter gets overheated
the insulation (nylon/fiber washers on the studs) gets soft and moves/compresses under the tension of the nuts
the nuts no longer clamp due to the now, softened and reset, nylon insulator damage
the studs and nuts are loose = more heat
Repeat
until you melt or wear out the insulation and one of the studs shorts to the case or mounting plate.
Dave
didn't work when i got the car
both leads on 1 stud and after testing i discovered it was shorted from the other stud to earth
it was removed from its position
the point where the studs pass through the metal support was dismantled
the old nylon and fibre washers that insulate the studs were thrown
new modern heat sink isolation collars and clear plastic/mica...(some odd stuff) used for insulating the earth tabs on power transistors was used either side of the plate, the thread of the studs was heat shrink wrapped to just past the metal plate, and the heat sink "Top Hat style" collars fitted from either side with a bit of smoothing and shortening, through the hole in the metal plate, thus insulating the studs from it in the same way as the original nylon did
i now have 3 layers of modern fire retardant insulation between the studs/nuts and the body of the ammeter/pod
the cable nuts are lock tight-ed and there is a spiky washer either side of the eye of the leads.
its been ok for 20 years... it might not be ok in the future but i feel i did a reasonable job of dealing with the usual problem.
Problem:-
Ammeter gets overheated
the insulation (nylon/fiber washers on the studs) gets soft and moves/compresses under the tension of the nuts
the nuts no longer clamp due to the now, softened and reset, nylon insulator damage
the studs and nuts are loose = more heat
Repeat
until you melt or wear out the insulation and one of the studs shorts to the case or mounting plate.
Dave
72RoadRunnerGTX
Active Member
The stock fusible link? What is wrong with fusible links? There is a reason fusible links were used over fuses in this charging/electrical system.
For one they were cheap.
70SwingerGuy
Long Haired Freaky Person
I bought this kit not long ago, it works really well, and cheap too!! We were talking about it last year back in this thread here:
Headlight Question
I used the relay kit that they provided cause although I want a kit from Crackedback, its just not cost effective with the exchange rate atm. Of course the light output is WAY better now!
autopar3000
Well-Known Member
Is that a glass lens, or polycarbonate?
The description says glass.
72RoadRunnerGTX
Active Member
That may be but that does not mean it was not the best choice for that particular application. I will continue to use fusible links there.
70SwingerGuy
Long Haired Freaky Person
Why would you use a fusible link instead of a fuse? Not being a smartass, just trying to learn.
72RoadRunnerGTX
Active Member
Fuse technology has improved significantly since these cars were designed but they can still fail at a much lower current than they are designed to open or quickly open on current spikes. An open or tripped fuse/circuit breaker used in this application means an engine stall if the car is in motion or a no start/dead in the water condition, a mission critical circuit application, same reason ignition 1 (ignition system) is not fuse protected. Fusible links tend to be more dependable (if its connections are maintained and not abused) and they react slower to the occasional current spikes in this stock charging system. There is a reason they were used there originally and it was not because it was cheaper.
Last edited:
Fusible links protect you from total disaster in some cases and do not open you up to nuisance trips/burns. It is crude protection. If you look at the curves on the Littelfuse Maxi slow blow fuses you can see these provide some nice protection assuming they work as advertised.
'Cuda_ragtop
Woulda, Shoulda, 'Cuda!
Auto Manufacturers still utilize fusible links in high current applications today, because they work in the applications they use them in. Since they are engineered, I wouldn't change those either.
Of course people do, but I see no advantage to changing a single spliced in wire, for a fuse holder, another wire and a fuse... more parts, more points of failure, one more fuse that could nuisance blow.
If you are going through fusible links, you have another bigger issue that needs to be addressed...
Just my 2¢ fwiw. Happy Trails.
Here is a link to some good Q&A on fusible links.
Fusible Link Wire FAQs
Some people will say that a fuse has 4 connections while a fusible link has only 2.
I'm not likely to go to the trouble of splicing in a fuse but was just pointing out the irony of so many posts recommending the updating of old technology, design weaknesses, etc. yet the fusible link is rarely talked about even though many are concerned about melt downs.
I'm not likely to go to the trouble of splicing in a fuse but was just pointing out the irony of so many posts recommending the updating of old technology, design weaknesses, etc. yet the fusible link is rarely talked about even though many are concerned about melt downs.
The concerning fail situations you mention are quite comical compared to today. My truck was "dead in the water" today because of an "electronic lock" originating from the stupid chip key. TG for google and the various forums out there.......Disconnect the battery and hook it back up.......Good to go.
72RoadRunnerGTX
Active Member
Some more load testing for this "Shunt wire" by-pass. 120+ amps on the stock wiring before any circuit protection opens?
Nice demo. I think you proved that most of the amps are going through the shunt wire. If the shunt wire had been suitably fused. Did you have a fusible link in it? If so it proves they don't work well other than to maybe prevent total melt down although you didn't go that far. With a suitable fuse in the shunt wire it would have tripped and then the stock fusible link burnt up shortly thereafter. It would be interesting to see this tested with a 30 amp MAXI slow blow fuse. Littelfuse publishes curves to show how fast the fuse blows over time with varying loads.
72RoadRunnerGTX
Active Member
Sounds like you may be missing the key point to the demo/videos. This is not about charging current from the alternator to the battery while in operation. It’s about total circuit protection from a short or overload condition. It really doesn’t matter what type of circuit protection devices are used (yes,12ga fusible link is present on that shunt wire). Some promote large battery cables and no circuit protection device at all on the shunt wire. The issue is if/when shorts take place anywhere is the stock unfused wiring components, or the shunt wire for that matter, now there is two paths for current to flow from the point of the short to the battery including the stock charge/load distribution path. Segments of the stock unfused wiring are now exposed to a large amount of current (much more than 12ga wires can handle safely) before any circuit protection can react, 120 amps in this case. You can’t wire circuit protection devices in a parallel circuit that will have any conductors that can’t handle the combined total current allowed by each circuit protection device and call it safe.
Last edited:
No I understood that. The MAD recommendation is 14 ga fusible link by the way. It does prove how fusible links provide little protection except from total disaster which is what I think the original design intended. With a short don't you think that you are going to melt something whether it is a connector or a wire before the fusible link goes anyway?
Mattax
Just the facts, ma'am
Yes. The purpose of the fusible link is to protect from a Battery short to ground while providing sufficient current carrying capacity to avoid resistance levels that will result in noticible voltage drops during normal operations.
72RoadRunnerGTX
Active Member
Did you get this wired in yet? If so, how was it and do you have the part number?
I’m trying to get the car assembled and running asap so I’ll do the upgrade down the road
www.forabodiesonly.com
Sealed Beam Headlights
Interesting thread on another forum: It appears ordering part number 81110-60p70 from a Toyota dealership gets you two Japanese-made Koito 7" H4 headlamps plus wiring and a relay setup for around $20. It's sold as a conversion for older Land Cruisers. No idea on how their beam pattern compares.
www.forabodiesonly.com
-
Similar threads
