Pep48 Posted October 2 Report Posted October 2 While poking around under the dash of my '48, I noticed that all of the mounting screws which attach the amp meter gauge to the dash are missing. These secure the meter to the dash panel. Now I guess that I can remove a screw from one of the other gauges and measure it... but I am far from being a Gumby and and I try to spend as little time as possible in that torture zone. (it can take me days to recuperate!) So, does anyone know size, length, and thread (fine or coarse) of those screws? Thanks! Quote
Los_Control Posted October 2 Report Posted October 2 100% not the answer to your question .... just a suggestion. I recently pulled the gauges on my truck which I assume are similar but different .... I'm prepping to paint the interior. What I'm baffled by, you can see I replaced the insulator gasket between the gauges and the housing .... Why the heck did I put it back together with the damaged insulator gasket between the amp gauge and plate? .... If I hooked up power to that amp gauge, it is extremely close to burning the wiring to the ground. The fuel gauge gasket is in very poor condition also. Dried up, curling, cracked ..... it needs replaced also. So thats my suggestion, when was the last time you inspected the insulating gaskets on your amp gauge? Think I might pick @desoto1939to write the official long term maintenance schedule .... At 75 year check up, replace insulator gaskets on amp gauge If there was any help I can give you on screw size I would, mine are different though. .... Maybe it is time to remove the gauge for inspection and replace screw in the process. Quote
desoto1939 Posted October 2 Report Posted October 2 This is Rich Hartung my handle or email is desoto1939@aol.com. I have read the above posting but I do not even remember commenting on the replacement of gaskets. Some gaskets are not even available to purchase to address every item on an antique car or truck. Sometimes when an issue is discovered and you have to make a repair is when you might find out that the gaskets or gasket might be back and then you might have a short. I can not say when you should pull your car or truck apart. Should it be every 5-10 or maybe even never unless a specific situation arises. The best that I can suggest is that you try to keep up with maintenance issues as best as possible. Rich Hartung Desoto1939@aol.com Quote
Los_Control Posted October 2 Report Posted October 2 40 minutes ago, desoto1939 said: I have read the above posting but I do not even remember commenting on the replacement of gaskets. But your reply is superb .... Honest, knowledgeable and straight forward ... also you prefer to keep the car exactly like it was when it rolled off the show room floor. If anyone could write a book on caring for a old car, you could ..... I mean that as a compliment .... I meant writing the book as a joke. Nobody expected these cars to be around as long as they have been, no books were written for it. I'm also a firm believer, sometimes things happen for a reason. ..... If a minor screw is missing, maybe it is time to investigate and find out why the screw is missing. For example, if the gasket dried up and shrank or fell apart, the screw would become loose and eventually fall out. While simply slapping another screw in to replace it is easiest .... maybe a closer look to see why is a better idea .... Quote
Young Ed Posted October 2 Report Posted October 2 I have a couple gauge clusters for P15s and can measure the thread. 1 Quote
rcl700 Posted October 3 Report Posted October 3 19 hours ago, Los_Control said: 100% not the answer to your question .... just a suggestion. I recently pulled the gauges on my truck which I assume are similar but different .... I'm prepping to paint the interior. What I'm baffled by, you can see I replaced the insulator gasket between the gauges and the housing .... Why the heck did I put it back together with the damaged insulator gasket between the amp gauge and plate? .... If I hooked up power to that amp gauge, it is extremely close to burning the wiring to the ground. The fuel gauge gasket is in very poor condition also. Dried up, curling, cracked ..... it needs replaced also. So thats my suggestion, when was the last time you inspected the insulating gaskets on your amp gauge? Think I might pick @desoto1939to write the official long term maintenance schedule .... At 75 year check up, replace insulator gaskets on amp gauge If there was any help I can give you on screw size I would, mine are different though. .... Maybe it is time to remove the gauge for inspection and replace screw in the process. I did not even know that this needed to happen, but does make since. What is used, cork or gasket paper? Should this be tested for continuity from back of guage to back of cluster. Don't the mounting screws tie the two parts together regardless of the gasket? Quote
Los_Control Posted October 3 Report Posted October 3 1 hour ago, rcl700 said: Don't the mounting screws tie the two parts together regardless of the gasket? It will need to be insulated I believe the correct wiring is from the starter to the input side of gauge, Direct voltage, and if the insulation fails you will have a weenie roast going on. This just happened to me in a different situation. I was having strange run issues and losing spark to the points. I could not figure it out, so I removed the distributor and bench tested it. When hooked up properly I instantly had the points catch on fire and had flames over 2" tall. Where the power wire from the coil connects, it is insulated from the case and also the point plate is insulated where it is attached to the distributor. I'm guessing with the distributor installed, the engine grounded to the frame grounded to the body acted like a big heat sink and absorbed the electricity. So there was a dead short, but no fire and no spark to points ..... The rubber insulation to the case was hard as rock and just fell apart when I removed it. Distributor on the bench the points got full brunt of the dead short and burst into flames. So I'm just paranoid right now. The amp gauge is same principle as the points ... need power to the points that needs insulated from all the metal around it. 2 weeks ago I would never have thought about this .... first the distributor fails, then I pull the gauge and see my insulation is failing .... This is my issue and you might be better off to ignore me. Same time it is, once you see it, you can not unsee it .... I'm looking at my insulation areas because I'm getting ready to build a wire harness and wire the complete truck. Quote
Sam Buchanan Posted October 3 Report Posted October 3 2 hours ago, rcl700 said: Don't the mounting screws tie the two parts together regardless of the gasket? I have the same question, what keeps the screws from grounding the meter to the frame? And is this even a concern? I assumed the gasket was to prevent dust from getting into the cluster and onto the gauge faces. Quote
Young Ed Posted October 3 Report Posted October 3 The ones for my p15 are 8-32 and very short. About .25 long 1 Quote
Sam Buchanan Posted October 3 Report Posted October 3 (edited) 53 minutes ago, Sam Buchanan said: I have the same question, what keeps the screws from grounding the meter to the frame? And is this even a concern? I assumed the gasket was to prevent dust from getting into the cluster and onto the gauge faces. Curiosity got the best of me so I went out to the P15 and put an ohmmeter across the ammeter body and chassis ground. The meter body is indeed grounded so the gasket has no electrical function. I still suspect it is to prevent dust in cluster. Update: Took a second look at the ammeter. Mine also has the little gaskets around the two mounting screws. Why are they there? Possibly to prevent the tip of a screwdriver from slipping off the screw head and coming in contact with the hot terminals on the meter???? I dunno.....I would disconnect the battery before poking around back there........... Edited October 3 by Sam Buchanan 1 Quote
JBNeal Posted October 3 Report Posted October 3 I had pulled the gauge cluster from the '48 1-ton awhile back so I pulled it off the shelf to clarify my fuzzy memories. The gauges are separated from the housing by cardboard about as thick as the gauge plate. The snap-in lights are not insulated from the housing. The amp gauge has cardboard cup-shaped insulators under both round head screw heads; there is not any insulation on the screw threads to prohibit contact with the gauge plate. The gauge plate mounting holes are concentric with the housing tapped holes, and the housing gasket and amp gauge cup-shaped insulators are tight to the mounting screws. Quote
Los_Control Posted October 3 Report Posted October 3 Ok here is what I see. With the gauge removed you can see I used cork because that is probably the closest I had to match the thickness of what I removed. If you look closely, the bakelite on the back of the gauge is recessed so the back of the gauge is flush ..... this is 2 ways the gauge is insulated from metal. Now if you look at the back of the gauge, the bakelite is actually proud of the back plate. .... Then there is a gasket that covers this area .... this is a 3rd way the gauge is insulated from metal. ..... you can see my insulator gasket just crumbled into pieces when removed. All ya All make up your own mind if it needs insulated. I'm going to do this while I have the gauge out and am running new wire. .... As far as gasket material I'm using Fel-Pro 3060 Just a random assortment of material that is nice to have around the shop ... I will be using the blue one for the back of the gauge .... closest to original. Quote
Los_Control Posted October 3 Report Posted October 3 I was going to add, if the gasket failed behind the gauge .... it is still insulated by my gasket going to the housing. If this is true, the whole back plate would be hot, not just the post for wiring ..... Is this a bad thing? .... you decide. Now if the gasket between the case fails ..... Bake lite or not, I think we will see some smoke ..... We have a couple of safety features installed, up to us to keep them functional. Quote
Dave72dt Posted October 3 Report Posted October 3 (edited) So far no one has bothered to answer the original question of how long and the thread pitch of the screws that hold the amp gauge to the dash plate. From what I can see from the pics posted the screws do not need to be very long, 1/4 to 3/8" should work, thread pitch may be 10-32 ( guessing ! ). Since they screw directly into the dash plate and the panel lights ground through the same plate I see no reason for the cupped washers unless it's to keep the amp gauge wires from maybe contacting them when installed. The big posts on the amp meter obviously need to be insulted from the plate. That would be a direct to ground short if they were not. I see now that Dodgeb4ya had made a guess to size and YoungEd did a physical check on his P15 as well as Andyd. Maybe OP will tell us what actually fit. Edited October 7 by Dave72dt Quote
Sam Buchanan Posted October 3 Report Posted October 3 (edited) We may be stumbling around with semantics, it seems there are two lines of thought in play. One line of discussion is about whether or not the meter terminals are isolated from the mounting plate. Yes, they are, by both the shape of the phonelic meter body and a paper gasket under and around the wire connections. The other thing under discussion is whether or not the mounting plate needs to be isolated from the metal instrument cluster with a gasket for electrical reasons. No, it is grounded to chassis via the two mounting screws. The gasket is there for reasons other than electrical isolation. If either of the two leads attached to the meter come in contact with the mounting plate a dead short to ground will occur because the plate is connected to ground irregardless of whether or not a gasket is present under the plate. The two screws provide a direct path to ground.....smoke/fire is released. Bottom line, make sure the harness leads can't touch the metal mounting plate because it is grounded. Here is the ammeter in my car, it appears to be an intact installation, but still not sure about the little washers around some of the screws. Edited October 3 by Sam Buchanan Quote
Los_Control Posted October 3 Report Posted October 3 37 minutes ago, Sam Buchanan said: One line of discussion is about whether or not the meter terminals are isolated from the mounting plate. Yes, they are, by both the shape of the phonelic meter body and a paper gasket under and around the wire connections. You scaring me Sam ..... and we are getting lost in the weeds. ..... One thing to consider also is positive or negative ground? Maybe on positive ground it does not matter so much. I'm in the process of going 12V negative ground ..... maybe I have a new issue not even considered yet ..... although others never complained when switching. As far as the OP original question, the screws are too small my tap/die set does not go that small .... only way I could find it is taking it to the hardware store and match it up .... I have spares so I can not answer that question. Quote
Sam Buchanan Posted October 3 Report Posted October 3 (edited) Polarity of ground makes no difference in this case, my ammeter has been wired both ways. I had to reverse the wires on the meter when going from positive to negative ground to make the needle swing the correct direction. My apologies for participating in thread creep! Edited October 3 by Sam Buchanan 1 Quote
Conn47D24 Posted October 5 Report Posted October 5 I made a cluster Gauge gasket template for my 47 Dodge and posted it here in the " Download " section. Hope it helps. Quote
andyd Posted October 6 Report Posted October 6 I just measured a screw which from memory came out of a gauge cluster for a 1940 Dodge and the screw is a 10NC24.....well at least thats the tap & die nut sizes that match the screw, I even screwed the screw into the die nut.....lol......its length is 7/16th.........dunno if this helps.....lol.........andyd Quote
Dave72dt Posted October 6 Report Posted October 6 8-32, 10-32 and 10-24 are all common sizes. grab 3 or 4 of each and crawl under the dash. Quote
Bob Riding Posted October 7 Report Posted October 7 Just measured my '51 dash screw -5/16" and thread pitch is 10-32 Quote
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