m925a2 not starting

[Cwynott]

hello i have a 1990 m925a2. it fried the alternator about a month ago. i replaced it with a delco style one. the other day when i went to go fire it up there was no power. the batteries both have 13 volts, also the wires going into the pcb have 26 volts. when i turn the battery switch i get a slight buzz then nothing and same with the starter switch. i need it to be up and running by next weekend for a parade any help would be greatly appreciated. i also changed the pcb out with a used one.

 

[adamsoffroadperformance]

sounds like a bad ground somewhere. check your grounds and your power wires that connect to the starter to make sure they aren't corroded or melted or burnt. wouldn't hurt to take the connections apart and scuff them up and reinstall.

 

[Cwynott]

thank you i will try that and see what happens.

 

[autoshopteacher]

I would do an individual battery test. Open circuit should be 12.6 VDC or above. 1/2 the CCA load for 15 seconds and the battery should not drop below 9.6 VDC at 60 degrees F. 13 volts does not mean the battery has the volume, amps, needed to work. On my 817 one low reserve battery (of 4) will give a no crank condition.

 

[Cwynott]

I load tested all the batteries. Then ran new wires from the batteries to the starter also new terminals. Cleaned up all the terminals on the starter. Still no power at the battery switch or starter switch. But there is 24+ Volts going into the pcm. Are there any circuit breakers or fuses I can't seem to find? Any help is greatly appreciated. Thank you.

 

[Doug Roberts]

and the used PCB might be bad

 

[Cwynott]

I just got a new one I ordered in the mail today. I'll try installing it in the morning.

 

[The HUlk]

I load tested all the batteries. Then ran new wires from the batteries to the starter also new terminals. Cleaned up all the terminals on the starter. Still no power at the battery switch or starter switch. But there is 24+ Volts going into the pcm. Are there any circuit breakers or fuses I can't seem to find? Any help is greatly appreciated. Thank you.

The buzzing you mentioned may be a solenoid inside the PCB not activating properly.

The battery switch should always have +24V on terminal A/wire 81A and +12V on terminal C/wire 569. When the battery switch is in the ON position there should be +24V on terminal B/wire 459 and +12V on terminal D/wire 569A.

The PCBox should always have +24V on pin C/wire 81. When the battery switch is in the ON position pin A/wire 459 & pin D/wire 5 should have +24V on them. When the ignition switch is in the START position pin E/wire 499 and pin B/wire 74 should have +24V on them.

 

[Cwynott]

Batter switch Terminal 81a has 24+ volts, terminal 459 has 24+, the other 2 terminals have no power coming from them. Pcb box wire 5 has no power when switch in on position also wire 74 has no power when in start position

 

[The HUlk]

Batter switch Terminal 81a has 24+ volts, terminal 459 has 24+, the other 2 terminals have no power coming from them. Pcb box wire 5 has no power when switch in on position also wire 74 has no power when in start position

Sounds like the power solenoid in the PCBox is bad.

 

[Cwynott]

I have a brand new one I will put on in the morning. I put 2 used ones on it. Do you think it could possible fry the new one?

 

[The HUlk]

I have a brand new one I will put on in the morning. I put 2 used ones on it. Do you think it could possible fry the new one?

No, they don't fry. The solenoids get old and wear out.

 

[The HUlk]

Also, the lack of 12V on the battery switch wires 569 & 569A should mean your heater blower is not getting any power. Wire 569 should be connected to the to the cable in between the batteries that has 12V on it.

 

[Cwynott]

When I was changing the battery cables I found 569 replaced the end and put it on the 12v side. I'll try the new pcbox in the morning.

 

[Cwynott]

The pcbox that is on there now when I turn the battery switch to the on position I hear it clicking. Could that be anything?

 

[The HUlk]

The pcbox that is on there now when I turn the battery switch to the on position I hear it clicking. Could that be anything?

When you turn the battery switch on, power is provided to the PCB box to activate the power solenoid. The solenoid has an electromagnetic coil that is supposed to pull a contact together which energizes wire 5. The click you hear is more than likely the coil activating. However when these fail it can be because the coil has gotten weak, the contacts are deteriorated, or a combination of both. No power on wire 5 is the telltale sign the solenoid is not creating a contact like it should.

 

[Cwynott]

Thank you I will install the new box first thing in the morning and get back on here. Before this issue came up from time to time I would have to rock the battery switch a few times to get it to turn on if that means anything else.

 

[The HUlk]

Thank you I will install the new box first thing in the morning and get back on here. Before this issue came up from time to time I would have to rock the battery switch a few times to get it to turn on if that means anything else.

That just further supports my suspision that the solenoid is bad. It is common for relay devices to become intermitent before complete failure.

 

[Cwynott]

I just put the new pcbox on and it fire right up. Thank you very much!

 

[adamsoffroadperformance]

make sure the click you hear isn't the abs computer clicking usually clicks twice.