MEP-805A voltage issues

[Blackmagic94]

Problems on this set I bought


runs and runs strong


1. water temp gauge has no reading. Pegged fully left of scale
2. Low voltage warning light is on
3. Ac interupter light up when pushed, lights up when switch is flipped, turns off when switch is released
4. 48 hz when on 60 ha setting. Doesn’t change with adjustment dials
5. 25-28 VAC will not adjust in L1-L2 position. Other positions move to zero vac

 

[155mm]

Have you tested magnetic pickup yet?

 

[Guyfang]

Have you ever seen this set work right?
Is it new to you?
Have you downloaded the TM's?

There are several things it could be, but first we need a little info from you.

 

[Blackmagic94]

The set is new to me. Last user was DoD so no clue on function


holding the run switch for 10 seconds you see maybe or even bumping while running the voltage jumps Maybe 5-10 vac

Battle short doesn’t change anything either.

what about doing the overspeed reset. I’ve read some of the tm

 

[Blackmagic94]

I also removed and inspected each relay and changed each fuse. The bus by the voltage regulator appears to have the 12 gauge bypass wires to protect the circuit if equipped with optimal which I am running 6tls which are brand new

 

[Guyfang]

Is there a big fat fuse next to the A1 volt regulator?

 

[Blackmagic94]

Is there a big fat fuse next to the A1 volt regulator?

Yes and I swapped another one in to it. But that one could be bad as well. I am getting dc alternator charging

 

[Guyfang]

That fuse has nothing to do with the DC charging circuit. It has all to do with producing AC voltage.
Do you have a multimeter? How about checking the fuse, before changing it with an untested fuse?
Get the operators TM and read the fist few chapters. It will help you understand what the set should and should not do.

 

[Blackmagic94]

Is the fuse reading vac or dc. I’m getting like a 0.1 vac on it

 

[Guyfang]

First off, did you test the fuse?
If so and its good, then when you hold S1 in the start position, On the A1 volt regulator, pins 7&8, you should get about 65-68 VAC, if the exciter is good and the A1 senses AC at the main gen. The 68 VAC comes through that fuse. So we need to know if the fuse is good, and if so, try and start the set. Hold the S1 in the start position. Also know, to get this set to work right, you have to hold the S1 up longer then what you are used to. So hold it up 6-8 seconds at least.

 

[Blackmagic94]

Will report shortly

 

[Blackmagic94]

Problems on this set I bought


runs and runs strong


1. water temp gauge has no reading. Pegged fully left of scale
2. Low voltage warning light is on
3. Ac interupter light up when pushed, lights up when switch is flipped, turns off when switch is released
4. 48 hz when on 60 ha setting. Doesn’t change with adjustment dials
5. 25-28 VAC will not adjust in L1-L2 position. Other positions move to zero vac

Swapped another used fuse. No vac 0.00

Do I put power on pin 7 and 8 and ground to chassis to test vac. If so I’m getting

pin 7
1.7 vac run
0.6 vac with switch in start held for seconds

pin 8
2.60 vac run
0.335 vac start

 

[Blackmagic94]

Actually fuse shows 2.2 vac and goes down slightly as you move s1 to start

 

[155mm]

Swapped another used fuse. No vac 0.00

did you test the fuse?

also, which fuse? The one on the back wall by a1 or the one in front marked ‘battery charger fuse’

 

[Blackmagic94]

The back one by a1. I know the front one works because I have dc charging

 

[Blackmagic94]

I’ll recheck it via ohms. Thanks

 

[155mm]

I Have chased my tail too many times to not verify something as simple as a new fuse being bad, test everything especially on a new to you piece of equipment that has issues

 

[Blackmagic94]

Every single fuse made the tone on my fluke

 

[Guyfang]

I also removed and inspected each relay and changed each fuse. The bus by the voltage regulator appears to have the 12 gauge bypass wires to protect the circuit if equipped with optimal which I am running 6tls which are brand new

What are you telling us here? By "Bus" do you mean the MT4 Battery Charging Ammeter Shunt? And what do you mean by "bypass wires"?

 

[Guyfang]

Now, to the MPU test and adjustment. Open TM 9-6115-644-24, to PDF READER page number 551. This is the adjustment procedure for the MPU testing and adjustment. Read it a time or two and test/adjust the MPU. If the set has a bunch of hours on it, I would just pull the MPU and test it. Then replace it VERY CAREFULLY, and by the TM. The TM tells you you are looking for 2-3 VAC, but the closer to 3 you get, the better. DO NOT adjust it any higher.