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  1. #1

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    Voltage Regulator Questions

    I recently bought a 1996 SL780 that seemed to be stuck in LIMP mode. After searching this great forum I have fixed most of my problems but still have a few questions.This ski had a bad ground that I relocated to the engine which fixed my MFD problems {Constant LOPR on display}.The display never displayed low fuel or HOT, but would not rev out past 4200 rpm and did not have a flashing red light. I took out the fuel sender and it tested out good and the float still would float. I tested the thermal sender which also checked out good.The only way it would rev all the way out was to disconnect the gray wire in the elec. box.Then I tested the LR54 regulator as per instructions in this forum and need someone to tell me if its bad.Voltage readings are as follows:3.3 volts from pink wire-13.2 volts from the tan wire-I could not get any voltage to register from the gray wire.Do you think this regulator is bad as I think there should be at least 3 volts from the gray wire.If its bad would it keep this ski in LIMP mode? Also would this be why there was no flashing red light on the MFD? Also if the oil tank is low will this cause a LIMP mode condition, I have heard different opinions about this? Thanks for any help...


  2. #2

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    Anybody?

  3. #3
    I'm addicted to Polaris PWC ghostinstallations's Avatar
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    How were you testing this module....everything still connected?

    Check the module output - MFD should not display overheat or low fuel. If either of these are being displayed, then they are the cause of your problem.

    Module Output:
    With the gray wire still connected, there should be some voltage on the line. If it shorted to groud (almost zero ohms or no voltage) then disconnect the gray wire and see if your problem goes away. If it does, continue (which in your case, you have already checked).

    Power Input:
    Red/Purple Should have 12 or more volts.

    Next, check your signal inputs: there are two inputs to the LR54, Pink (Low Fuel) and Tan (Overheat). They need to be tested to determine if the module is bad.

    Overheat Input:
    From your readings, there is voltage on the tan wire, indicating that the overheat sensor is not grounding out and there is NOT an overheat condition (Good).

    Low Fuel Input:
    I would disconnect your fuel sender (Pink) from the LR module and see if the problem goes away. Disconnecting it should tell the module you have a full tank of gas. If you problem goes away, then you need to check the fuel sender. Otherwise the LR54 is bad:

    Fuel Sender Check:
    Disconnect the pink going to the fuel sender and test for resistance to ground. Full shoud be about 30 ohms and empty should be about 240 ohms. IF it is good, but disconnecting it from the LR54 fixed your issue, the LR54 Fuel input portion is bad.

    If the LR54 is bad:

    You can replace it or leave the gray disconnected. You will still be alerted on the MFD of an overheat condition or low fuel. Just be smart enough to not go full throttle if you run into an overheat condition.

    If you decide you want to replace it I have one for sale.

    Hope this helps!

  4. #4

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    Thanks for the reply. I tested the LR54 both with it connected as normal, And with the gray-pink-and tan wires all disconnected from the board.The results were the same with no voltage from the gray wire.My fuel sender checked out good.If my LR54 was connected correctly and is defective, would this limit my rpms? Disconnecting the pink wire from the LR54 does not solve my problem. Thanks again...

  5. #5
    I'm addicted to Polaris PWC ghostinstallations's Avatar
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    Yes, the unit could fail shorted, which would cause your problem. Not unheard of. So you can replace it or just leave the gray wire disconnected. PM me if you are interested in a replacement LR54.

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