kramttocs Posted March 11, 2020 Share Posted March 11, 2020 I'd say splices 102 & 103 are where I'm connecting and extending to the PDB. And, as you've figured out, they aren't under the dash. In Big Blue's case they are on the passenger's fender liner, and I'll show a pic in a bit when I get back from a meeting at church. But you kept L & M and replaced J w/a 60 amp? It was the 'Near Fuel Tank Selector Switch T/O' that was throwing me off with those splice locations. Correct. Granted, I had put together this change as my first foray into making wiring changes on the truck so I am interested in all of your findings and if I need to change anything. My post on this change is here and this is where the 60 was recommended: https://www.ford-trucks.com/forums/1570236-1-wire-alternator-and-voltmeter-rewire-diagram.html I hadn't really thought about it since then though so glad you started this thread. I am not sure the 60 is correct and now with the blower relay mod, it may be way off. Link to comment Share on other sites More sharing options...
85lebaront2 Posted March 11, 2020 Share Posted March 11, 2020 Ok guys, thanks for the input. You've given me a lot to think about. Jim - You said "I believe Bussmann & Littelfuse produce ultra slow blow fuses meant to replace them, and equivalence ratings are shown." I'll go looking for that info. Did we talk about it recently? Bill - Your Chizzler info is helpful. Summarizing: 20 gauge is 20 to 40 amps 18 gauge is 40 to 50 amps 16 gauge was omitted but 60 to 80 amps 14 gauge was omitted but might be 100 to 120 amps 12 gauge is 160 amps Scott - I will have to splice short pieces of wire in as well, but am ok with doing that. I have another harness from which I can get the same wire so the sizes and colors will be consistent. But, at this point I'm not addressing any fuselinks at the aux battery solenoid. All - I understand that fuselinks don't fail very often. But having gotten down to fuselinks L & M, which are buried pretty deeply in the harness, I'd sure hate to have to replace them while on a trip. (I'll post pics in a bit of where they are.) And, as shown in the schematic below, I'd really like to replace the stuff in the orange rectangle below - Fuselink J and the shunt. But if Fuselink J is replaced by a fuse then it needs to support both fuselinks L & M. So why not replace them instead and not have anything for Fuselink J? Gary, on Fords, so far I haven't had one fail, Matt did on his 1986, the one from the alternator, which promptly took out the 2G alternator. Chrysler, had more than a few fail, and on the FWD models all except the hazard flasher are clustered if a fan shape near the bulkhead connector and are a royal PITA to fix, hence the nice PDC in the konvertible. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 11, 2020 Author Share Posted March 11, 2020 Gary, on Fords, so far I haven't had one fail, Matt did on his 1986, the one from the alternator, which promptly took out the 2G alternator. Chrysler, had more than a few fail, and on the FWD models all except the hazard flasher are clustered if a fan shape near the bulkhead connector and are a royal PITA to fix, hence the nice PDC in the konvertible. Bill - I haven't had one fail either, but I've helped quite a few people on various forums or on Facebook that have had problems with fuse links. Maybe because they did something dumb, but it does worry me. As for where these things are, here's a pic of where all these things are. You can see that fuse links L & M are way down on the fender apron and would be difficult to change while on the road as you have to get to S102 and S103. And don't forget that all of this is normally covered with many turns of electrical tape. It probably took me over 15 minutes to get this much stripped back. Link to comment Share on other sites More sharing options...
kramttocs Posted March 11, 2020 Share Posted March 11, 2020 I'd say splices 102 & 103 are where I'm connecting and extending to the PDB. And, as you've figured out, they aren't under the dash. In Big Blue's case they are on the passenger's fender liner, and I'll show a pic in a bit when I get back from a meeting at church. But you kept L & M and replaced J w/a 60 amp? Did some very quick looking and seems like 60amps is a pretty common consensus for a 16ga fuse link replacement so I feel safe leaving it as is. As has been mentioned in this thread also, most of those threads have a comment somewhere about there not being a straight conversion. Since as you [Gary] said the fuse ratings add up well beyond 60 in this case so I don't know if one could even drop the fuse (that replaces the fuse link) amps down if they eliminate a few of the heavy draws. But... Fuse Link L - the headlight relays reduce a significant portion of the load Fuse Link M - the blower relay reduces a significant portion of the load. Additionally, are you keeping the aux battery connected through this circuit? I ask because if you are use the smart isolator with the boost functionality, you will be running a larger cable and can eliminate this aux battery load as well as the trailer lamps/brakes from this circuit. For instance I have a fused 1/0 running from the main battery to the smart solenoid and then a fused 1/0 from the smart solenoid to the aux battery and am leaving the Yellow wire disconnected from the solenoid (used to be the junction block) at C232. That way the 1/0 handles both the aux battery and those trailer circuits. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 11, 2020 Author Share Posted March 11, 2020 Did some very quick looking and seems like 60amps is a pretty common consensus for a 16ga fuse link replacement so I feel safe leaving it as is. As has been mentioned in this thread also, most of those threads have a comment somewhere about there not being a straight conversion. Since as you [Gary] said the fuse ratings add up well beyond 60 in this case so I don't know if one could even drop the fuse (that replaces the fuse link) amps down if they eliminate a few of the heavy draws. But... Fuse Link L - the headlight relays reduce a significant portion of the load Fuse Link M - the blower relay reduces a significant portion of the load. Additionally, are you keeping the aux battery connected through this circuit? I ask because if you are use the smart isolator with the boost functionality, you will be running a larger cable and can eliminate this aux battery load as well as the trailer lamps/brakes from this circuit. For instance I have a fused 1/0 running from the main battery to the smart solenoid and then a fused 1/0 from the smart solenoid to the aux battery and am leaving the Yellow wire disconnected from the solenoid (used to be the junction block) at C232. That way the 1/0 handles both the aux battery and those trailer circuits. I had planned to use Fuse Link M and the big yellow wire to continue to serve the aux battery. The reasoning there is that the EFI wiring has a very large wire running from the battery/my PDB to the EFI PDB on the driver's side. So I don't want to run a new wire just to replace it when I do the EFI. But you are correct that the headlight relays and the blower motor relay will take fuse links L and M, respectively. Link to comment Share on other sites More sharing options...
81f100custom Posted March 11, 2020 Share Posted March 11, 2020 I had planned to use Fuse Link M and the big yellow wire to continue to serve the aux battery. The reasoning there is that the EFI wiring has a very large wire running from the battery/my PDB to the EFI PDB on the driver's side. So I don't want to run a new wire just to replace it when I do the EFI. But you are correct that the headlight relays and the blower motor relay will take fuse links L and M, respectively. A few interesting reads on fuse links. http://www.starquestclub.com/forum/index.php?showtopic=107395 https://www.whiteproducts.com/fusible-faqs.shtml https://www.wiringdepot.com/jt-t-tech-articles/Fusible-Link-Wire-FAQs This statement here is somewhat right but just using what standard wire size is rated to carry in amps. 18 gauge fusable links are rated at 14 gauge wire or 15 amps , 16 gauge are rated at 12 gauge wire or 20 amps. The fusible link that protects the wire should then be two gauge sizes (or four numbers larger). Looks like most I have read agree on they are not rated like fuses but more so engineered for what they are protecting. What are the ratings for fusible links? Fusible links are not rated in amps like fuses because each installation is unique and designed to meet specific circuit protection requirements. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 11, 2020 Author Share Posted March 11, 2020 I had planned to use Fuse Link M and the big yellow wire to continue to serve the aux battery. The reasoning there is that the EFI wiring has a very large wire running from the battery/my PDB to the EFI PDB on the driver's side. So I don't want to run a new wire just to replace it when I do the EFI. But you are correct that the headlight relays and the blower motor relay will take fuse links L and M, respectively. 81f100custom - I see you've replied while I've been working on my post, so I'll reply to yours in a bit. Ok, I've done some measuring. And I've included a chart from Offroaders that Jonathan pointed out. Plus, Scatch pointed out the calculator at WireBarn. I've used both of these on the observations below. However, the table doesn't say what voltage drop it is allowing, but I've been able to determine that it is apparently using a 3% drop for the conservative #'s and a 5% drop for the others by comparing it to the WireBarn calculator. Which voltage drop is "right" for our trucks? I don't know, but I think it varies by the device you are powering. For instance, lighting doesn't like much voltage drop or you lose a lot of light. On the other hand, the radio doesn't care too much, although you may have to turn the volume up slightly to accommodate a lower voltage. Also, I've found that the wire that Ford used is ~.135" in diameter for a 12 gauge conductor, and ~.175" for a 10 gauge conductor. And I'll probably have to fill that in for other gauges as we go on with this..... So here are two of the wire sizes and current capacities: Ckt 37: The yellow wire that goes from S102 is a 10 gauge and the run is 7' long to S208 that feeds both the ignition switch and the fuse block. (It is another 1' on to the switch and the fuse block, but they are fed by their own wires so that doesn't count.) The table below suggests that #10 can support right at 65 amps, but that would be pushing it. But the WireBarn calculator says that at a 5% voltage drop #10 can support 90 amps up to 7.68'. However, if you hold the loss to 2% you can only carry 40 amps for 6.91'. Ckt 38: The black/orange wire that goes from S103 to the headlight switch is a 12 gauge and the run is 8'. The table says 20 amps is about right for it, and WireBarn agrees that you can run 20 amps out to 8.69' with a 2% loss. On the other hand, WireBarn says #12 is good for 50 amps out to 8.69' with a 5% drop. Meanwhile, back at the ranch, I've researched the slow-blow fuse idea. And I haven't found any - yet. I did find this page on the Littelfuse site that says "The MAXI® fuse uses “Diffusion Pill Technology” to provide predictable time delay characteristics and low heat dissipation." And then provides the chart below. So, I called Littelfuse. The first person I talked with didn't think they have slow-blow fuses in the Maxi size, but said he'd get a technician to email with me on it. So far there's been no response. Now I'll go read 81f100custom's post and reply.... Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 11, 2020 Author Share Posted March 11, 2020 A few interesting reads on fuse links. http://www.starquestclub.com/forum/index.php?showtopic=107395 https://www.whiteproducts.com/fusible-faqs.shtml https://www.wiringdepot.com/jt-t-tech-articles/Fusible-Link-Wire-FAQs This statement here is somewhat right but just using what standard wire size is rated to carry in amps. 18 gauge fusable links are rated at 14 gauge wire or 15 amps , 16 gauge are rated at 12 gauge wire or 20 amps. The fusible link that protects the wire should then be two gauge sizes (or four numbers larger). Looks like most I have read agree on they are not rated like fuses but more so engineered for what they are protecting. What are the ratings for fusible links? Fusible links are not rated in amps like fuses because each installation is unique and designed to meet specific circuit protection requirements. Ok, 81f100custom, I've read all the links. The Starquest guys appears to be just like us, another group of guys that are struggling through this but don't have any specific technical credits to their names. But White Products and Wire Barn are not just guys like us - they are manufacturers and/or vendors. However, their pages are identically worded, so it suggests that they may have gotten the wording from elsewhere. Maybe an official site? In any event, it does carry some weight. And while fuse links aren't specifically rated, like fuses, there has to be a current rating range for each size. And the automotive engineers then select the fuse link to fit the current the devices on that wire will pull. That's the "engineering" they do. However, some of us are "re-engineering" these trucks. For instance, Fuse Link L was sized to support the headlights as well as the other lighting. But I'm moving that current off to fused relays, and that's probably about half of the current on that circuit. Similarly, I'm going to power the HVAC blower's high speed, where it pulls the most current, via a fused relay. And since the A/C-Heater circuit is fused at 30 amps, a bunch of amps are going to be pulled off of Fuse Link M. So, I'm playing "engineer" in this case. But, I'd like to do it correctly, and appreciate your input. It has given me more to think about. Link to comment Share on other sites More sharing options...
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