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A/C and the fuse box |
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GAclassic65
AMC Apprentice Joined: Nov/29/2019 Location: GA Status: Offline Points: 39 |
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Thanks gentlemen, that's the kind of reality feedback I need to hear. It's Dang hot now in GA, and warm wind through the windows aint all that thrillin' anymore:) I'm leaning towards taking the A/C for an evaluation on the matter to someone who also knows A/C systems and AMC vehicles.. With that being said, my question would be does anyone here in this forum know or have any contacts info with AMC enthusiasts/clubs, that I could find to point me to someone. Or if someone here already knows of some mechanics that would be in my part of the country where I could go? Please do tell. I'm in north GA, about 50-60miles north of Atlanta Thanks all.
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GAclassic65
AMC Apprentice Joined: Nov/29/2019 Location: GA Status: Offline Points: 39 |
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So I start out just to explore options to get my A/C running ... And now may have run into another issue altogether w/ the fuse panel. To the eye it looks very good and clean and no signs of any water damage. However the 20amp fuse for the heater Blower and-or A/C, gets very hot when a load is applied. I checked the fuses and some were the wrong size ( a 7and1/2 amp fuse where a 9amp should be, and a 4amp where a 9 should be )I also looked closer at the largest fuse for the Blower and A/C and it actually had a 30 amp in there... which is the size AMC says you should use if you have an A/C car. I swapped our everything for new correct fuses and put in a 20amp for now for the heater blower. I tested it out again and ran the heater blower. After a few seconds the 20amp again stared heating up, but this time I felt more closely while it ran, and it was actually one side of the fuse holder for that fuse that got very hot, eventually too hot to touch. The fuse itself a little less so, though still hot, and the other side of the fuse holder ... hot but not as hot as the first side. I believe the heat is originating from the one side, and then radiating down throughout the fuse to the other side of the holder. Looking at my wiring diagram ... the fuse holder side that's getting hot first and gets the hottest, is I think the ignition side. At least on the diagram it's the brown wire coming from the key ignition that's in line with the "hot" side of the holder. So changing the fuses made no difference. Open for ideas on what to do next?
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7544 |
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It's not the fuse. Fuses are nothing more than a piece of wire, sort-of calibrated to fail at a particular current.
I can't see yours of course, but it's extremely common for the plating to corrode off where the clip touches the fuse. Then give it 50 years, the tiny bit of extra resistance from it just being a friction connection turns into a real problem. Like a crack in a dam it gets worse then fails quickly. It's possible too that there is something wrong with the blower motor and it's drawing a lot of current and pushing things to the limit (and those limits are lower, due to the above). But if one end gets hot before the other, that's a bad clip. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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GAclassic65
AMC Apprentice Joined: Nov/29/2019 Location: GA Status: Offline Points: 39 |
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I see. Thanks It looks pretty easy to pullout the Fuse panel, all I see are two screws holding it in place. If so, how difficult is it to replace those clips, can you just pop them out and pop in a new set? Are clips universal fit items? Where can they be bought ... local Napa etc...? This seems like if it's a straight forward operation to do, then it would be good first test to try ... and we may get lucky and it'll fix the problem.
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Heavy 488
AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3552 |
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You aren't going to be able to replace the clips. Gently clean them up a bit on the contact area then pinch them tighter
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GAclassic65
AMC Apprentice Joined: Nov/29/2019 Location: GA Status: Offline Points: 39 |
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Okay, so I unscrewed the fuse panel ( 2 screws ) and there isn't really anything underneath. I did notice the section of metal that the 2 screws connect to, around each screw hole, there was a grey colored substance w/ the consistency of silly puddy or tar... rubbery and it crumbled off. So the fuse panel did not sit flush against the metal bracket that it screws too, but had this grey stuff sandwiched in between acting like a gasket. I don't know if that should be there or not, but since it began to crumble off I cleaned it off, and replace it with a black tar-like item that has the same constancy... but can be removed if it shouldn't be there. I took some sand paper and cleaned the clips but just the one that was getting hot, then I finished them off w/ some contact cleaner and finally gave them a good pinch so they would grab tighter on the fuse. Re-attached everything, turned on the heater blower, but the fuse 20amp fuse clips hot again. Should I clean all the clips? Is there a better way to clean them or does my problem lie elsewhere?
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7544 |
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I've not had good luck rejuvenating them. They're constructed from two thin sheets of phenolic insulator, some then metal bars for interconnects and faston connections, and some springy alloy clips, riveted in place.
The clips and connect bars seem to have a slight dissimilar-metals corrosion issue, and cheap, thin plating, add current, a slight (millivolt) potential difference, then decades of time, and it all corrodes. A fraction of an ohm resistance creates a lot of voltage drop = heat. If indeed the problem is the fuse panel, then replacing it might be the best approach. There are various ways to measure the actual current drawn by the load, easy enough if you're skilled and equipped in electronics, but fraught if you're not. I suspect though that the fuse panel is shot. Is this the only fuse making you crazy? One way to test this theory would be to find those fast-on connectors, pull 'em off the AMC panel, and add your own separate inline single fuse holder. If THAT burns up, OK! you have a "load" problem! But if it solved your fuse panel problem you at least have a short term reliable fix. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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GAclassic65
AMC Apprentice Joined: Nov/29/2019 Location: GA Status: Offline Points: 39 |
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Yeah electrical thinking is not my forte. I found a place that I feel good about taking it to have them look it over. But I like your approach, and will be sure to mention what you say here to them ... especially cause w/ you I know it comes from a fellow who knows these AMC cars. I chatted about the issue with the owner of the garage ( they don't work on cars past the 80's decade) and he feels good they can track down the fuse issue and get the A/C operating all in one fell swoop ... I'll proceed w/ caution. Will let you know...
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george w
Supporter of TheAMCForum Joined: Jan/27/2013 Location: New Jersey Status: Offline Points: 2899 |
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I would suggest that when you have the fuse panel out that you use a brass wire brush and carefully wire brush all the fuse clips and male connecting terminal surfaces along the edges paying particular attention to the inside surfaces of the clips that contact the fuse caps. You also want to make sure that the fuse clips are bent in such a way that they grip the fuse tightly. You also need to check to make sure that the rivet that attaches the fuse clip to the circuit board is tight so that the clip makes good contact with the metal buss bars on the back side. If the clip is loose then drill it out and replace it with a small, short brass bolt and nut that you can get at just about any hardware store. These clips have to be tight.
As for the fuse rating, the larger fuse size was specified for a/c cars as that blower fuse had to handle the additional current draw of the compressor clutch as well as the power needs for the blower motor. Some heat at that particular fuse is normal as a steady current flow of anywhere from 20 to 30 amps through that fuse will generate some heat in the fuse element that will pass into the metal caps at the end of the fuse glass. The rated amps of a fuse is not the current that the fuse will blow at but the current rating that the fuse will hold. Keep in mind that when a fuse is being operated at it's rated capacity the internal element will be getting hot, not red hot, but hot. If the current going through the fuse exceeds the rated capacity of the fuse by a certain percentage AND a certain length of time the heat will melt the element and the fuse "blows". If the over current draw is minor the fuse will take longer to blow or may not blow at all but if the current exceeds the rating of the fuse by a larger amount then the fuse will blow much more quickly. There are fast blow fuses and slow blow fuses and, depending on the engineering specs of the fuse, the time that the fuse can withstand a overload is written into the spec as to the amount of overload and the time that overload is permitted for that type of fuse. For example: a fuse spec. rating may be 20% overload for 20 seconds, 50% overload for 5 seconds and 100% overload for 2 seconds. A truly severe overload will blow a fuse instantly. This time / current spec is true for all fuses and circuit breakers as it allows for initial turn on in-rush current surge that all electrical devices have. That's why there are so many types of fuses that may all the same current rating yet operate much differently when overloaded. It's important though that the fuse clips have tight contact not only to the fuse itself but also to the metal buss bars that connect everything together. Any resistance in the contact surfaces consumes power that should be going to the load, causes a voltage drop to the load and will create heat at the contact point. Contact surfaces should be shiny clean AND tight. |
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Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7544 |
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good info, george w!
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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