MEP-805A voltage issues

[Blackmagic94]

What relay powers the coolant temp gauge

 

[Guyfang]

No relay controls the coolant temp gauge. Can you read schematics? There is a wire direct from MT6 to M6. It passes through a plug and TB, but no relay.

 

[jmenende]

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.

Hi Guy, I have the same undervoltage problem with my 805a. The voltage drops once I release S1 even after 10 seconds. I have a libby AVR and changed the capacitor for good measure but Im only getting 60VAC on pins 7&8. The hertz show low but when tested its adjustable to 60hz and speeds up the engine. The rheostat shows no effect when turning the dial. Mi model is older and does not have the upgraded external fuse. any ideas as to why im not getting 65-68 VAC ? Thanks.

 

[Guyfang]

Is this gen set new to you?
Have you ever seen it run right?
Do you have the TM's downloaded for this gen set?

I would advise doing the Quad fuse improvement, ASAP.
Have you worked on this set? Or someone else?
You say its a Libby A1. Have you looked to see if all the other components of the volt regulation system are Libby parts? The attachment is a list of parts to check.

 

[jmenende]

Is this gen set new to you?
Have you ever seen it run right?
Do you have the TM's downloaded for this gen set?

I would advise doing the Quad fuse improvement, ASAP.
Have you worked on this set? Or someone else?
You say its a Libby A1. Have you looked to see if all the other components of the volt regulation system are Libby parts? The attachment is a list of parts to check.

Will check each part. I learned about this mix and match the hard way. I have two 805a, one libby and the other trc. I put the TRC avr on the libby and the avr started smoking. Yikes.

 

[jmenende]

Is this gen set new to you?
Have you ever seen it run right?
Do you have the TM's downloaded for this gen set?

I would advise doing the Quad fuse improvement, ASAP.
Have you worked on this set? Or someone else?
You say its a Libby A1. Have you looked to see if all the other components of the volt regulation system are Libby parts? The attachment is a list of parts to check.

I cant find R16 in my 805a control box. Can you point me in the right direction please. The manual has no mention when I search for it.

 

[jmenende]

All my libby parts match exept r16 which i could not find. These are the test results. I think i have en exitor problem.

 

[Guyfang]

Look behind this panel. Should be hooked to the Freq select switch.

 

[Guyfang]

All my libby parts match exept r16 which i could not find. These are the test results. I think i have en exitor problem.

The T1 wire on the reconnection board, (TB1). TB1 is located inside the right rear top door. There are about a million wires hooked to it.

I dont think its a excitor problem. The main gen makes power. Just not enough.

 

[jmenende]

The T1 wire on the reconnection board, (TB1). TB1 is located inside the right rear top door. There are about a million wires hooked to it.

I dont think its a excitor problem. The main gen makes power. Just not enough.

I agree, tested the exitor leads and got a 28.2 reading. Close enough to the 3 ohms.

 

[Guyfang]

I would think it could only be the A1 or a main gen diode.

 

[jmenende]

R16 resistor is showing 10.5 ohms instead of the 3k in the manual. Im going to replace it.

 

[Guyfang]

Did you isolate at least one side? If not, you get a false reading.

 

[jmenende]

I temo

Did you isolate at least one side? If not, you get a false reading.

I removed the diode and tested it. Thats how i got the 10.5 ohms on r16

 

[jmenende]

I would think it could only be the A1 or a main gen diode.

A1 diode as in a bad avr board? Where is the main gen diode located?

 

[Guyfang]

Main Gen Diodes. they are in the rear of the main gen.

 

[jmenende]

Main Gen Diodes. they are in the rear of the main gen.

Ok, I will test those tommorow since I already removed the bell housing to get to the exitor. Thanks again.

 

[jmenende]

Im not clear on what values i should be looking for when testing the main gen 1n1190/r diodes.

 

[Guyfang]

There is probably a Diode function on you multimeter. Its more or less like checking ohms. What you want to see is continuity in one direction, and none in the other.

 

[jmenende]

I know how to check the diodes but was wondering if there was a voltage parameter that I should be looking for.