Joined: Nov 18, 2010 Posts: 75 Location: San Juan Island WA
Posted: Mon Dec 05, 2011 12:55 pm Post subject: using 24v gauges in a 12v system
It's a contradiction, right?
The only thing I don't like about the 12v conversion is that the original gauges (which were all in the extra box of parts from the PO) can't be used with the 12v system. The PO put in some poor quality chrome-bezeled gauges which work but look
I'd sure like to use the original gauges if I could- nothing else compares to them; is there any means of doing so, say with a step-up converter/transformer? I researched some- they're mostly from China nowadays, that cover a good range of wattage and amperage, using voltage from 8-18 volts and converting to 24v and run <50 bucks. They claim they are suitable for automotive use.
Anything to this or is it just a lonely, fruitless search.....? _________________ 54 M38A1 delivered 2-54
53 Strick M100 #79
70 DJ5A
Joined: Nov 24, 2010 Posts: 1390 Location: Orem, UT
Posted: Mon Dec 05, 2011 1:30 pm Post subject:
I believe all can be used. The oil, speed and temp are mechanical. Amps are amps. I think you have to do something with the fuel sending unit though, but I cant remember where I read that. _________________ Brett
'51 M38
PHOTO DIARY OF MY BUILD
2 - The Oil Press is electric using a sender, both are 24V.
3 - The Coolant Temp is electrical using a sender, both are 24V.
4 - The Fuel Gauge is electric using a sender, both are 24V.
5 - The Amp meter is in fact an extremely sensitive volt meter that interprets the signal (voltage) across the shunt in the regulator and displays it on a dial face calibrated in amps.
1 is a no brainer.
2 thru 5 are very voltage sensitive and will NOT read correct values on 12 volt.
If you just do not want to buy and install the huge GI 24V 25A regulator, Generator and harness then just buy a new 24V 50 to 100A Delco alternator for between $100 and $200 dollars and press on.
Finally you can temporarily replace 2 thru 5 with a set of auto 12 volt/mechanical gauges for around $45. 12V for the voltmeter and mechanical for the rest. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Nov 18, 2010 Posts: 75 Location: San Juan Island WA
Posted: Mon Dec 05, 2011 3:21 pm Post subject:
Bretto wrote:
I believe all can be used. The oil, speed and temp are mechanical. Amps are amps. I think you have to do something with the fuel sending unit though, but I cant remember where I read that.
Well, the speedometer is certainly mechanical and it looks and works great. Now, those pesky fuel level, oil pressure and water temp gauges are the issue; on the A1, they are electrical. Both sending units (along with the 24v fuel tank sending unit) are in the box of spare parts I got with the jeep. The ammeter simply reads a charge or discharge, maybe it would stand up to a 63 amp alternator, but I'd prefer to put in a voltmeter.
The original gauges have another advantage: they have the slots in the case, just behind the bezel, to allow the light in from the dash lights which provide the correct red light. _________________ 54 M38A1 delivered 2-54
53 Strick M100 #79
70 DJ5A
As I have already said above the amp meter will not work correctly on 12 volt because it is actually a sensitive volt meter using a shunt located in the voltage regulator. Direct reading amp meters (those that allow the full current load to go through them) will work no matter what the voltage. This is not the case with your 24 volt military amp meter. I have always encouraged a switch to the military 24 volt volt meter because it offers more information about your electrical system then the amp meter will. But here again the 24V military volt meter's color coded ranges won't work for 12 volt. You will have to remark the face of the gauge. Civvy auto gauge kits come with internal lighting and you just redirect your gauge lighting power to them. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Nov 18, 2010 Posts: 75 Location: San Juan Island WA
Posted: Mon Dec 05, 2011 4:00 pm Post subject:
Wes, we were posting at the same time and I hit the submit button not realizing you had answered the questions.
So I could go ahead and hook the original 3 sending units back up and get accurate readings from the oil, water temp and fuel gauge, huh? Interesting that the PO didn't do that.
The ammeter is not going to be put back in, though per your earlier suggestion of a voltmeter in the glove box, I could just put the ammeter back in the panel but not hooked up to anything. Stewart warner sells a 12v voltmeter that looks pretty close to the mil24v one if you paint the bezel; I was just looking at one on ebay.
Yeah, I have thought about just going with a 24v alternator; in my web travels I noticed they are not uncommon and would bolt up to where the 10si alernator goes. Then I go back to buying 24v headlights, etc.
As far as replacing the gauges with aftermarket ones, that's what is already on the panel and which I'd like to get rid of- they are just too far off the "look". I have some old school mechanical Stewart Warner gauges - the full sweep ones- with black backgrounds and white pointers. By painting the bezels OD, they'll look much closer to original than the cheap orange pointer ones on there now.
But if I can use the original fuel, water and oil gauges, without burning something up in them, then that may be the way to go. _________________ 54 M38A1 delivered 2-54
53 Strick M100 #79
70 DJ5A
So I could go ahead and hook the original 3 sending units back up and get accurate readings from the oil, water temp and fuel gauge, huh? Interesting that the PO didn't do that.
No I did not say that.
Quote:
But if I can use the original fuel, water and oil gauges, without burning something up in them, then that may be the way to go.
As I already said above they will not read correctly.
The only difference between your Delco 12V SI and a 24 V Delco SI is the voltage output.
The commercial 24 volt headlamps are significantly cheaper than the military with the pig tails.
You only lack a 24 volt generating source and starter from being stock and I cannot understand why you just don't pop for the 24 volt Delco alternator and run the stock parts you like so much anyway.
My M38 has a Delco 24 volt alternator and my M37 has the late Military 24 V 60 amp alternator. I prefer to drive and enjoy rather the wrench every day on them. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
The answer is 24 volt gauges will not give accurate readings on 12 volt _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Nov 18, 2010 Posts: 75 Location: San Juan Island WA
Posted: Mon Dec 05, 2011 10:40 pm Post subject:
Thanks for the clarification, I thought that might be the case.
With nearly 6000 posts, something will get missed; thanks again for all the insight into the jeep's electrical system. _________________ 54 M38A1 delivered 2-54
53 Strick M100 #79
70 DJ5A
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