Still waiting for parts so out with the meter again.
As suggested using the cowel battery with the engine off I get a battery reading of 26.8 volts, with the ignition on but not running I get 26.0 Volts,
with the engine above 1500rpm I get 30.2 Volts.
The generator as you know gives me 27.90 Volts at the starter.
If those are all okay bar the 30.20volts will be interesting to see if the new voltage regulator brings it down to the required 28.5 Volts.
I did not realise that the two 12v batteries gives a bit more than 24 Volts!
I did not realise that the two 12v batteries gives a bit more than 24 Volts!
Every day is a school day.
Actually you are reading the combined value of both batteries and this not only peculiar to 24V/28V systems. 12V/14V will show the same indication of voltage greater than the nominal battery voltage but less than the system rated voltage for a fully charged battery setting at rest.
The nominal voltage of the common batteries are: 6V, 12V, 24V.
The system voltages of systems that use these batteries are: 7.5V, 14V, 28V.
Charging voltages in these systems are greater than the system operating voltages.
Fully charged voltages for these batteries are: 6.5 - 7.0, 12.8 to 13.0, 25.0 - 26.0. (Note: A fully charged voltage reading does not always mean an actual fully charged & healthy battery. That is why you must also measure the electrolyte's specific gravity during testing.)
A reasonable working knowledge of lead acid batteries and their maintenance is necessary to successfully and properly maintain and test them. Download this recent (1998) version of the Army's Battery Maintenance Manual TM 9-6140-200-14 1998 Care & MX batteries:
Note the 2HN battery in the M38 is still an active battery model in this 1998 manual!
Also do not overlook Battery Maintenance web links on our web links page under Technical How To websites (Batteries). _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
The new Voltage regulator arrived today from the U.S.A which is an electronic unit,sorry Wes nobody knows about the original ones in this neck of the woods.
Before I install the unit the instructions say to remove old unit and check the resistance between the field and ground.Divide 24V by the measured resistance. If the result is greater than 2AMP, the excessive field could damage the G225OP.
Could you tell me which parts to put the meter on in simple terms?
Also bus voltage, not sure about this.
Last. Do not connect the unit to a generator with a ground shorted field?
Before I install the unit the instructions say to remove old unit and check the resistance between the field and ground.Divide 24V by the measured resistance. If the result is greater than 2AMP, the excessive field could damage the G225OP.
Could you tell me which parts to put the meter on in simple terms?
When you disconnected the two plugs to change the regulator, one went to the firewall harnes and one went to the generator. The conduit on the generator cable assembly is the ground between the regulator and the generator. The 3 wires inside it are: A - Armature, B - Field, C - Armature. You attach the red lead of your Ohmeter to the B terminal pin and the Black lead of your Ohmeter to case of the generator.
Also bus voltage, not sure about this.
Buss voltage refers to the working voltage throughout the electrical system in the jeep. Usually electronics folks limit this definition to the Buss Bar which in most applications is where the generator/battery's output is connected to a distribution bar which has all the circuit breakers or fuses connected to it for the distribution of power to the jeep's various electrical systems.
Last. Do not connect the unit to a generator with a ground shorted field?
A generator with a shorted field would have indicated 0 resistance with your ohmeter connected to the B terminal and the generator's case.
That illustration is an M38A1. The M38 had the plugs on the regulator facing aft. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Interesting how they swap things about.
You would think the connections would be better pointing backwards.
On with the new Voltage regulator.
After testing as per instructions from Wes I got a good reading of .03amps for the resistance from field B to the generator case.
So I hooked up the new unit, at idle I get 28.2 V which is good but as I rev the engine 30.07V.
The instructions on the Voltage Regulator say that if the measured voltage is different than 28.5V look for dirty or defective Gen output circuit breaker or field circuit breaker /switch.
Thought I would run a real time test with the new regulator.
So i went for a run with the cowel battery hooked up to the volt meter and after things settled down I got a reading of 31.10 V at 30 to 40 mph,so not good.
Went back and fitted the original Regulator and did the same run out and got a reading of 29.80V, so a bit better.
So after all that back to square one.
So looking for advice on cleaning dirty or defective Gen output circuit breaker.
The instructions on the Voltage Regulator say that if the measured voltage is different than 28.5V look for dirty or defective Gen output circuit breaker or field circuit breaker /switch.
Now that could be a problem since there is no such animal on your M38. The output of your new voltage regulator is fed thru #4 wire to the starter terminal where it connects directly to the cowl battery's 24V positive cable and thru # 10 wire where it connects to the individual circuit CB's on early M38 or to Wire #'s 11, 15 & 25 for routine distribution on late M38's.
You should post a copy of these instructions you have for the transistorized regulator. I would like to read a copy on my own. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Never addressed, as far as I see in this thread, what meter type are you using?
When was the last time it was calibrated? What quality is it? Is it made in China?
I believe you indicated that your M38 has a voltmeter in the dash as opposed to the original style ammeter?
If it has a voltmeter it probably has a tiny partial line about midway through the green scale. Only the very early voltmeters don't have that line.
While driving, where is the needle in regards to that little partial tick mark? My guess (and its only that) is that the needle is pointing right at that mark?
If the needle is pointing to it, then you may have been chasing your tail beca
use of an out of calibration handheld voltmeter. _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
Hi.
Thanks for the reply.
The original was made in the U.S.A the new replacement is from Mid West also made in the U.S.A G2250P Texas Electrical Systems.
The Volt meter is a Unit-t UT132 Series made in Hong Kong and gives good reading as far as I know.Not been calibrated.
The meter on the dash is spot on the pip when running. Bought a N.O.S one so nice and clear.
As you can see from my results the original voltage regulator gives a lower Volt reading than the new one with exactly the same set up and temp conditions.
The batteries have not boiled but I have not been on longer runs than three quarters of an hour just in case. They, the batteries are new when the Jeep was sold to me. As i said in one of my firsts post am I being fussy over 1 Volt i.e. 29.80 v not 28.5v but the new one runs at 31.10V.
I have certainly picked up a lot of information on the subject thanks to Wes Etc.
If it is running on the pip in the dash gauge, you are good to go. If you are still concerned, put the one with the lower voltage back in and start enjoying your Jeep. _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
The lower voltage one is back on, just did not know how accurate these gauges are over a modern volt meter and still curious why the brand new regulator runs even higher.
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