Carrier 750 MT Generator

[Chris2005]

Hi All,

Is there anyway of checking the generator on a carrier 750MT,

I suspect the generator on the lorry has failed but no fault codes are appearing on the cab controller is this normal.

Regards

Chris

[phil Landon]

hi there Chris, not to sure if it is the same setup as A 950MT. Inside the control box on the side of the unit is the fan relay module ( it is a black square box about 2 in square and sits near the top above the defrost contactors. You should see some fuse holders mounted on the relay module. Pull out one of the fuses and see if there is any voltage, be careful as it will be around 220-240 V AC. If there is no voltage try looking at the generator capacitors. ON the 950MT they are 8mf and are attached to the micro door. If they are faulty they can cause the generator to fault as well.

I have just finished replacing a generator and fan relay module after a meltdown on a 950MT.

If you still have no luck then check all the connections back to the generator, other than that the generator has probably failed.

hope this helps

[123smc]

Hi Chris, what are the symptoms? No evap fans? Fans in one compartment only? As above suggested check the fan command board fuses haven't blown. Check the wiring from the generator to the control box, a broken wire will stop the generator producing voltage. There should also be a generator test plug (4 pin) inside the control box.

[Chris2005]

Hi,

Thanks for the reply,

the symptoms I am having is no evap fans are working at all,

I have checked both capacitors on the door and both are fine, I have also checked at the blank plug that is connected to the generator wires but no voltage is present when unit is in operation..

The plug and wire is good back to the generator.

I am going back to the lorry this evening and will let you know how I get on.

Many Thanks

Chris

[moggy66]

have you tryed re-flashing it?

[Chris2005]

Hi,

I have tried putting a a small battery to the capacitor terminals that are situated on the door while the unit is running.

But to no effect , still no power.
Does the generator go completely when there is a fault or should it be putting out power on some of the windings?

Regards

Chris

[moggy66]

the blank plug you mention is that the red and blue wires from the gen? if so flash it there with 12V? if it doesn't come up then i suspect the gen

[IRMechanik]

is your belt tight? Don't mean to be condescending but it does need to be pretty tight.
Do your meter check capacitors? Check the two 8 uF caps in the control panel. Not very familiar withe the 750mt and may be slightly different from the north american version. Does it have low and high speed? If it does, there will be car (capacitor alternator relay) that will switch out one of the capacitors for high speed these were good for melting down on the R90s. If the capacitors and the relay all check out, good bet the generator has failed. If your standby motor is 230vac (again not sure of non-na units it may be 460vac) you can rewire the fans to run off the standby motor unless you're 460vac in which case you're sol.

[Chris2005]

Hi Moggy,

I will be in the yard again tomorrow sometime,
When you flash from the blue and red wire on the test plug , is it blue and any red or is it a specific red?

Thanks

[moggy66]

the red and blue that goes to the Generator

[jakemigz]

Hi Chris2005 check the tightness of the belts first, check the resistance of the of the Stator Auxillary Coil stud 5&2 the resistance reading should be 12.2 ohms for Supra 750MT, checke also the resistance of Stator Main Coil stud 6&1 stud 3&4 the reading should be 1.7 ohms for Supra 750MT. please give me your email I will send you the Operation and Service Manual for Supra MT series. Do you get any voltage on the diagnostic connector inside the control box the blue and red wire, when there is no load what voltage you get? there is a diagnostic procedure on the manuals I have this will help you to solve the problem. I did encounter that kind of problem many times and I managed to sorted it all.