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Voltage Regulator problems

in 912 / 914 Technical Questions 6 years ago
I seem to have been plagued with VR problems. I've gone through 2 Ducatti VRs and at least 2 John Deere VRs. Two symptoms prevail: either the VR terminals look black, clearly overheated, or the voltage just seems gradually decrease. In all cases, the VRs are too hot to comfortably touch.

The installation is in an RV-12 in the inside the cockpit, under the avionics shelf location.

Currently, the VR is just grounded via the standard mounting bolt, to aluminum shelf path. I'm about to install a heavier duty grounding cable to the VR, thinking that I might have a grounding problem.

If the added ground wire doesn't improve the situation, I'm thinking there might be a problem with the 22,000mF capacitor. There's supposed to be one in the RV-12 switch module but if that's either not there or is defective that would be a problem. So,would there be a problem adding an external capacitor if the internal one is there and working? If not, would any old 22,000mF/25v capacitor work or do I need a special one? In other words, where do I get one?

I'm kind of grasping at straws here. This doesn't seem to be be a very complicated system yet there must be something wrong at the rate I'm going through VRs. Any other ideas?

  • Re: Voltage Regulator problems

    by » 6 years ago

    How many amps is your maximum load?
      
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  • Re: Voltage Regulator problems

    by » 6 years ago

    Here are some things I have done to address R/R issues on my RV-12:

    -- Relocated R/R to Van's recommended location under the avionics shelf.
    -- Run a @ 7/8" air blast tube from the side air vent to the R/R fins. I also route the "baby's breath" exhaust air from the avionics compartment towards the R/R.
    -- Installed a dedicated ground lead (same gauge as used for battery connections) from the R/R mounting lug to the engine.
    -- Minimize electric consumption when at low RPMs and maximize electric consumption when at high RPMs.
    -- I regularly see 13.9 volts and 1 amp in cruise. I tend to disregard all other volt/amp indications unless I see a strong discharge rate/minus amps = failed R/R.
    -- I carry a spare Ducati R/R in my travel bag.

    My current Ducati R/R has now lasted some 525 hours over 3.5 years. I believe that heat (internal and external), vibration, and shoddy construction combine to cause these R/Rs to fail in our RV-12s. YMMV.
      
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  • Re: Voltage Regulator problems

    by » 6 years ago

    Having not enough load, too much load or too much external heat will kill the VR. Vans is too much external heat and zip for cooling.

    First you are right about needing a good ground. The metal firewall should have been okay, but running it to a know good ground can never hurt.
    I've posted this on the Vans forum, but everyone just wants to blame the VR and not the mountings. .
    The Vans fix is not a good one because it is in dead warm air space and just gets too hot. I have 5 RV12's I see and have made this configuration change and none have had any issues. First the original location mount of the shelf behind #4 exhaust pipe is way too hot and vans covers it with a metal box they think is getting air, but their setup pulls more hot air over the VR.

    Do this instead:e
    Get some 1/2: tall plastic bushings and raise the VR up off the metal service so there is that 1/2" air gap. Run a good ground wire from the VR to a good solid ground. Next up where that 1" black tube is inserted into the air intake plenum, just loosen it from the silicone and stretch it out another 1 1/2" and face it forward into the air stream. Now you will have a forced positive pressure cool air going over the VR. Silicone the tube on the inside of the plenum with a touch of silicone and take some safety wire through the outside wall of the plenum in and around the black tube to make sure it never moves out of place.
    Now wrap the #4 exhaust pipe (all 4 if it were me) in 2" wide header wrap cloth. This will reduce radiated and convected heat to the VR drastically. Now you have dropped the VR external heat by a huge amount.

    Using header wrap on all 4 exhaust will reduce radiated and convected heat and the Mfg says up to 70%, but I don't always believe those numbers, but even if you reduced the heat to you wire insulation, plastic fittings and hoses that a lot over the run time of the engine and parts.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Voltage Regulator problems

    by » 6 years ago

    The black VR connectors are very suspicious to me. Those spade type connectors have been troublesome to several folks. Make sure the female side is pinched down very tight; many of us have also replaced the Ducati multi-connector plug and installed individual connectors.
      
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  • Re: Voltage Regulator problems

    by » 6 years ago

    Thanks for the suggestions. I added a dedicated ground from the VR all the way to the engine this afternoon. I didn't have time to see if that had an effect, hopefully I'll be able to do that tomorrow.

    My installation is in the Van's revised location inside the cockpit under the avionics tray. I've tried mounting a small muffin fan in that area but haven't been able to come up with a decent mounting for it that's effective and not in the way of the passenger's feet/knees.

    dheal, does your 7/8" blast tube on the right side entirely block that vent, redirecting all the airflow to the VR, or did you split it between the blast tube and cockpit ventilation? I'd be interested in how you did that, would it be convenient to take a picture sometime?

    Not sure what the maximum load is. It's the standard RV-12 load. My impression is that's in the 75% - 80% range of the "generator" capacity but not sure about that.

    No one said anything about my question about the 22,000 mF capacitor. Am I barking up the wrong tree in thinking that might contribute to the problem?

    Thanks again for the responses.
      
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