ML amp cutting out - United Radio tested and no trouble found - Possible speaker issue (1 Viewer)

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Joined
Mar 2, 2021
Threads
2
Messages
9
Location
Gilbert, Arizona
2008 GX470 with Nav / Mark Levinson amp

ML Amp would work for various time periods before slowly losing volume with a light crackle noise for 5-10 seconds, and then would go into protection mode/ shut down.. After a few minutes of the car sitting powered off, starting it back up, the ML amp would work again for a few minutes until it did the same thing and would shut down again.

After a bunch of forum reading, I assumed it was just the dreaded failed amp.. Thus I called United Radio and sent them the unit to test/repair.
United Radio tech calls me and says no trouble found with the amp.. He ran it for a while and does not see any issues.

He then mentions that I may have a bad speaker where ohm readings less than 6 ohms may cause the amp to shut down.

Before I start tearing things apart, I'm looking for advise where to start testing. I don't see any pin out diagrams from the Amp to Speakers where I could test ohms from the harness without having to go directly to the speakers.

If I do need to pull door panels off to test, does it make sense to unplug the speakers and try running the amp for periods of time to try to find the issue by process of elimination, or will just a multimeter ohm test tell me enough ? Lastly, I cant seem to confirm the Ohms for the sub. Is that 8ohms as well

Appreciate any and all help as I yearn to get my audio working again.
 
I'd probably just pull the door panels and ohm out each speaker to see which ones are failed/etc. You'll be able to inspect for torn cones and other damage as well at the same time.
 
Update:
1) Ripped door , cargo, and subs rear qtr panels off and tested all speakers for ohms and condition. Center speaker housing pops off to remove that so thankfully did not have to remove the head unit to get to it.
2) All speakers tested fine for expected ohms and actually look great.. No damage at all. Both front tweeters were abt 5.8 ohms but I don't think that's out of line to cause any issues
3) Tested multiple iterations of balance and fade hoping to remove power to certain speakers.
4) Sub is 8ohms single voice coil for those still wondering.

Result:
1) After amp seems to heat up initially for @ 30min or so, music begins to clip slowly, then progressively the clipping gets worse until the point that it sounds only like a crackling noise coming thru.
2) Loss of any volume control or volume display on the Nav unit
3) Turning the stereo off then back on gets me no sound at all
4) Only turning the car /accessory power off for a period of time seems to allow the radio to work again
5) The shorter time the car is off, the less time the radio/Amp will run before clipping starts and goes to only a crackle
6) If the car sits with radio/Amp powered off for overnight, I'll get @ 30 min again until clipping to crackling only
7) Amp fans are working fine

I'm thinking its heat related as the amp and components heat up over time to the point the Amp no longer functions normally.
United Radio did not say to what extent they ran tests, but what they did get was a cold amp that probably tested fine for the time period the tech either ran it or looked at it.

Any ideas from those that may had similar issues?
Could the single DIN radio unit be bad? I don't see any mention of them failing .

I may just send the amp back again to have them look at it.
 
Tweeters are actually 6ohm in the ML system so that makes sense.

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Update:
I was betting on the Amp and decided to buy a used one from a junkyard on ebay .. It was guaranteed to work and was a great price.

I installed the amp and it played perfect upon turning the radio on. I was happy and hoping for good things.. Then about 30 minutes in, same symptoms, music slowly begins to clip, and progressively gets worse till the point that only clipping /crackling noise.. Exactly the same symptoms as my original Amp that United originally said tested good.

So now I have 2 amps, both that seem to be good
All speakers were tested for correct ohms
All speakers are actually in great condition as well

I guess the only thing left is the head unit unless anyone else has any ideas of what it could be..

When you all say head unit, is it just the single DIN radio/cassette deck only, or that and the Nav screen unit as well?
 
The head unit is just the single DIN/radio/cassette portion. The head unit and the display operate independently. I don't think it's possible for the display/NAV screen to have any bearing on your issue.
 
UPDATE:
Head unit swapped
Amp swapped and tested by United Radio
Speakers checked for correct Ohms and condition
Speakers unplugged 1 by one and Audio tested for possible shorts.
RSES unplugged
Console ripped open and wiring checked
All wires behind head unit checked
Voltage checked

After each attempt to troubleshoot, the problem remains the same, so its something else that no one seems to have encountered yet. Maybe a short, bad ground, who knows..
Net/Net. I'm so frustrated and have given up on this whole process trying to save the existing system.

Actions now:
CD Changer has been removed
I unbolted the head unit wiring block, untaped wiring harness, and stretched the head unit wires to get to the back of the glove box
Head unit is now mounted where the CD Changer was in back of the glove box.
AMP /CD Changer / All speakers will be removed and sold to create my replacement fund
Replace front & rear door speakers, as well as the sub
Buy new Single DIN Radio
Re wire speakers
Add 5 Channel amp (Front / Rear / Sub)
Center speaker delete .. Not being reused
Cargo door speakers delete. .. Not being reused

Question:
Can the existing Nav run off the mid range speaker in the door.. I believe its currently the 6x9 that plays the audio??

Feedback on replacement items please:
Radio - Looking at a Kenwood BT728HD .. $150 is my budget. Thoughts?
Amp - Kenwood X802-5 5 Channel , 50W RMS x 4 plus Sub 300W .. I do not want 2 amps. Thoughts on this amp or others. $350 range.
Sub - I saw a video of a guy who installed a Skar 6.5" that came out good.. AMP will be 4ohm, thus a 2ohm sub & wire dual voice coil in series. I do not want a Sub box.
Front door speakers - Thinking I should go component 6x9s with crossover mounted in the door vs going coaxial, then reuse the mid for Nav. Any thoughts on brand? Kicker KS Series is what I see so far as a potential option.
Rear door speakers - 6.5" Coaxial for sure to mirror existing . Any thoughts on brand? Kicker KS Series looks to be a good option here as well
No center or cargo door speakers

I figured I would continue this thread vs stating a new one as I found way too many threads that started with problems, but never closed with the ultimate solution.
 
Last edited:
Question:
Can the existing Nav run off the mid range speaker in the door.. I believe its currently the 6x9 that plays the audio??

The NAV plays through the drivers door 2.75" speaker. You'd have to retain the amp and reroute to the dash speaker if you want it to work.

My build thread might be of some help to you:

 
FINAL UPDATE:
New install is done.. After some tuning of the new decks settings, the new system sounds great.. I'm about $1k into it

Kenwood KMM-X704 Single DIN deck - $140
Kenwood X802-5 5 channel amp - $350
4ga power and ground to the amp - $20
All new speaker wiring and RCA twisted pairs from the deck to the amp for L /R/ Sub - $40
Skar 6.5" sub, 2 ohm wired in series to get 4ohms. - $55
Kicker KS 6x9 2 way Components in the front (tweeters mounted in original location using a backstrap to hold them in - $250
Kicker KS 6.5" Coaxials in the rear doors - $110
OEM Pioneer HU moved to back of the glovebox where the CD changer was after removing wiring harness block and taped wires in the harness.
BT mic ran and clipped to the Drivers side A pillar up high.
Aux port removed and replaced with a USB Vigo input - $15

Delete ML amp , Delete Center speaker, Delete Cargo door speakers, Delete CD Changer, Delete OEM Sirius XM receiver.

4 sale soon: My plan is to come out net zero on out of pocket cost
ML amp - $375
OEM door speakers- TBD @$50 ea - $400
Sub - $200
CD changer and Sirius XM - TBD

Note, you do lose OEM voice navigation and OEM phone bluetooth with the removal of the ML amp, but its a terrible Nav anyway.
Bluetooth will run from the new deck for both phone and streaming. For Nav when needed, Waze will be used from my mobile device with bluetooth sound broadcasted the new audio system.

I also did lose steering wheel controls as I'm not sure how to tap into those with this specific setup since the OEM deck remains in the glovebox

Still upset that I had to go thru all this for a GX with only 120K, but I guess the ML amp would have failed at some point costing me $575 at least..
 
Curious, why did you keep the OEM headunit plugged-in inside the glovebox?

For the steering wheel controls, you can probably use one of those universal kits to add it to the new headunit. You might need to cut the wires for the steering wheel controls that run to the OEM headunit so you're not controlling two headunits at once.
 

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