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Voltage Regulator problems

  • tomkk
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2 months 2 days ago #19444 by tomkk
Voltage Regulator problems was created by tomkk
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?

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2 months 2 days ago #19445 by kenryan
Replied by kenryan on topic Voltage Regulator problems
How many amps is your maximum load?

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2 months 2 days ago #19448 by DHeal
Replied by DHeal on topic Voltage Regulator problems
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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  • Roger Lee
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2 months 2 days ago #19450 by Roger Lee
Replied by Roger Lee on topic Voltage Regulator problems
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)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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2 months 2 days ago #19452 by jiott
Replied by jiott on topic Voltage Regulator problems
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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2 months 2 days ago #19455 by tomkk
Replied by tomkk on topic Voltage Regulator problems
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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2 months 2 days ago #19456 by DHeal
Replied by DHeal on topic Voltage Regulator problems
Regarding my blast tube: I used a small 90 degree PVC pipe elbow and shaped it somewhat to press fit into the top half of the side vent opening. Glued the plastic flex hose into one side of the elbow and used a bit of safety wire to aim the other end of the hose at the R/R -- it was a prototype installation but I never felt the need to further refine it. Yes, it steals a bit of the blast air from the passenger's vent but there is more than enough air flow remaining for the passenger's use. On really cold days when the vent needs to be closed, it is not hot enough to need to worry about the extra R/R cooling of the blast air.

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2 months 2 days ago #19457 by tomkk
Replied by tomkk on topic Voltage Regulator problems
Thanks, I'm going to give that a try ...

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2 months 2 days ago #19458 by joe9253@yahoo.com
Replied by joe9253@yahoo.com on topic Voltage Regulator problems
It is unlikely that a bad capacitor is causing the Voltage Regulator to fail. It will not hurt to add another one if you want to. As other have said, forced air cooling is recommended because heat can cause electronics to fail. Have you mounted your voltage regulator with heat conductive paste? It might help to insert a 0.063" x 5" x 5" aluminum plate between the voltage regulator and the instrument panel base. Put heat conductive grease between the plate and the instrument panel base and between the plate and the voltage regulator aluminum case. The idea is to get rid of the heat via both conduction and convection.

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2 months 2 days ago #19459 by tomkk
Replied by tomkk on topic Voltage Regulator problems
Thanks, I did try some heat conductive grease back some time ago. Now I'm trying the opposite - standing it off from the panel base somewhat to try to get some air flow behind it. My thought was that the base of the VR is mostly, I assume non-heat conductive, potting compound of some sort and the only heat conduction from the base is through the fairly thin metal edge surrounding the potting compound. Don't know if that makes sense or not. Neither mounting method seemed to have much affect on the heat dispersion.

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2 months 2 days ago #19461 by joe9253@yahoo.com
Replied by joe9253@yahoo.com on topic Voltage Regulator problems
Like you said, the potting compound will not conduct much heat, so blowing air on it will not help much. Here is another idea: Use the aforementioned aluminum plate but stand it off from the panel base and blow air around it. You could attach a thermocouple to one of the regulator mounting bolts. Omega part number WTJ-6-60-TT should work. The Red wire is negative. Connect the thermocouple wires to the EFIS.
Joe G.
The following user(s) said Thank You: Dennisr5

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2 months 2 days ago #19462 by tomkk
Replied by tomkk on topic Voltage Regulator problems
Hmm, not a bad idea ...

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2 months 2 days ago #19463 by RobSeaton
Replied by RobSeaton on topic Voltage Regulator problems
If you run the engine with the master OFF the regulator will fail.
unless you have a servicable 22,000mf capacitor installed.

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2 months 2 days ago #19464 by tomkk
Replied by tomkk on topic Voltage Regulator problems
Nope, haven't done that. Is that the only function of the capacitor?

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2 months 2 days ago #19466 by RobSeaton
Replied by RobSeaton on topic Voltage Regulator problems
Yes, it acts like a battery if if the ship battery is disconnected.

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2 months 19 hours ago #19472 by tomkk
Replied by tomkk on topic Voltage Regulator problems
Just an interim update here. I added a ground wire to the VR mounting that provided a clear, positive ground back to the battery ground and to the engine. That might have helped the heat problem somewhat but it was so slight it could have easily been my wishful thinking.

I added a blast tube like DHeal suggested. It was almost embarrassingly easy to put one in. I got some 7/8" ID plastic tubing from Lowe's. It was on a roll so when they cut off my 2' the tube had an inbuilt curve that was perfect to get from the side vent to the front of the VR. Anyway, a couple of clamps to the avionics tray base and I had a blast tube. I flew it today and I think this was the first time I've ever been able to comfortably hold my hand on the VR. It provides a small amount of airflow from the prop while on the ground but a real good airflow in the air. Surprisingly, it didn't seem to cut down the airflow into the cockpit from the right side - important here in Florida.

Now that I can keep it cool, I'll be interested in seeing if it lasts longer.

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