doclouie

Larry,

I am wondering what the blue wire of the amp fan goes to or does. Do you know?

This is the fan data sheet.

https://www.delta-fan.com/Download/S...412VHD-R00.pdf

Davesrave

Not sure about yours, but PCM 3.1 has a setting that toggles the touch screen on/off. Might want to check that.

larrysb

Need to get the *exact* model number the fan, as it is on the sticker.

I thought it might be the -F00, which the blue wire is the "tach" or frequency function.

https://www.delta-fan.com/Download/S...412VHD-F00.pdf

Need to know if it is the -F00 or the -R00 fan.

They come in 4 varieties:

1. 2-wire just power +/-. Fan runs full blast.

2. 3-wire, power +/-, and 1-signal which is the fan tachometer. It pulses at the speed of the fan rotation. Most common type from computers. Usually, third wire is blue. The computer mother board controls fan speed by lowering the voltage supplied to the fan power and monitors the tach signal to see how fast it turns.

3. 3-wire, power +/-, and 1 signal wire which indicates if the fan is locked. Aka, fan-fail wire. Usually yellow, but varies, no standard color. Used in things that don't do speed control, but might want to shut down if the fan gets jammed.

4. 4-wire, power +/-, and 2 signal wires: 1 usually blue, is the tach signal. The 4th wire is an input called PWM, which controls how fast the fan turns instead of lowering the power voltage. Allows very slow speed and quiet control.

When I looked it up, the first string of numbers is the fan model family, and there's a suffix on the label somewhere that id's what the 3rd wire function is.

vg247

Super big thanks ‘Davesrave’ - it somehow was indeed toggled to touch screen off, turned it back on and all is well now. Many many thanks..

doclouie

It is a 3 wire fan with the third wire being blue. I backed off in replacing the caps right now as I want to be very systematic in the approach. I am going to replace the fan first just because I have never known it to be turning. You can easily tell by reaching under the seat. It may not be turning for two reasons: the fan blue wire is sending signal back that is incorrect or the circuit board is not sending a signal to turn on the fan. The fan black and red wires make it turn so I am going to see about maybe bypassing the board and running the fan whenever the ignition is on. This cut out happens so infrequently that it will be a long process to figure out as I rarely travel far in my car. The manufacturer and exact part number of the fan is

Delta Electronics Inc. EFB0412VHD-5D42.

The blue wire seems to be a tachometer. There are many different fans that are very similar. I think the -5D42 means that the blue wire is the tachometer and has the same connector as with our cars. The only question I have is will the fan still run if the tachometer is not working properly? I will get the right fan on order today.

Update: Disconnecting the blue wire does not turn on the fan on.

larrysb

-5D42 means it is a custom part.

It could be a tach wire, or a fan-fail wire. The 5D42 means it was custom ordered, no doubt for the special connector and the metal threaded bushings.

I googled the part number and found some surplus:

https://store.cwc-group.com/efb0412vhd5d42.html

For $10, with the connector and everything.

It is easy to test the wire function. For either tach or fail sense, the output is open-collector, meaning it needs an external pull up resistor. So if you connect a 10k resistor to +12 (or whatever to power the fan) and power the fan, you can look at it with a scope or even a voltmeter. If the fan spins up and the voltage goes to zero and stays there with the fan spinning, and it goes high if you lock the rotor with your finger, then it is a fan-fail type. If the scope shows a square wave or it the voltage on a voltmeter is something between ground and +, then it is a tach.

doclouie

That is the fan I ordered this morning. 4-8 days to ship it from California to Texas.

Bruce In Philly

Update:

Thanx Larry, I just ordered that fan.... cheap, fans are common failure points.... why not?

No cutouts. I have been driving two-hour drives each day for the last few days.... one hour out, one hour back..... stopping for gas... shutting down the car.... restarting... key in.... key out.... and PCM is still working. Wow. And ambient temps over 90 degrees. Again, I am NOT declaring "problem solved".... but something good is happening with just the application of the the thermal paste.... or maybe it was just the removal and reinstall of the fan that got it working.... I dunno. doclouie, excellent idea with the paste.

For source material, I've been listening to The Doors 5.1 DVDs, NPR (telling me how awful I am), and basic radio (jazz, classical, rock). I am purposely playing the material on the loud side to stress the amp.

So... let's assume the paste works.... surely something else is actually failing or failed and the paste is just lowering the thermal threshold for triggering the failure... no? It may just be a temporary bandaid... or one that lowers the cutout frequency. I think there is something wrong with the unit and worthy of a real repair.

Would the application of paste on the chips also lower the temps of the main caps? Would the heat energy flow over the board to the improved sink on the chips?

Keep going guys.

Peace
Bruce in Philly

doclouie

Haven’t received my fan yet to install, but yes thermal paste makes all the difference. One point is that, at least with my amp, there was no thermal paste between the board and the outer metal cover/shield. Adding that definitely will help pull heat out of the board although not as well as if the cover was aluminum. Any heat pulled out of the board reduces the heat of surrounding components for sure. Heat kills components and the cooler they are usually the longer they last.

The fan type they put into our cars has two varieties. One has a 2,000 hour mean time of failure and the other is a 70,000 hour mean time failure. I am sure it is the 2,000 hour, but because it is custom we may never know. They would have saved a few dollars on the 2,000 hour one.

Good datapoint Bruce. Keep driving and keep us posted. I have a 10-15 minute commute so mine never shows signs unless I am in a multi hour drive, which is rare. I just wonder if that new fan will turn when I install it. Hopefully it is just a thermal thing. More fun to come.

BucketList

I don't know that you will find a fix that works for everyone. Amps fail for different reasons. There is one shining star here in that they are not failing outright so maybe a combination of fixes will work for most if not all scenarios. I think you guys are on to it. 2 main issues, power supply and cooling. If the power supply is working as designed, cooling is less of an issue, but as the components age they tend to run hotter (for technical reasons having to do with those caps) so then cooling becomes more important. Swap the caps and the fan and grease the heatsinks will probably get it for most cases.

larrysb

Well, the thermal paste allows heat conduction from the hot thing to the cool thing. It's there to fill in the microscopic gaps from surface roughness between the heat-sink and the heat-source. So, improved cooling of the amp chips will reduce the amount of heat that goes through the circuit board and everything else. The chips used in the amp have metal tabs to carry heat away, on both the exposed side and the board side. Most boards like this have a copper layer that is stitched to help conduct and spread heat away from the chips. It gets distributed through the layers of the board and other components. Most is intended to go out of the chip through the exposed metal tab to an external heat sink.

Bose did a decent job of building this amp. It is competently made. The paste doesn't last forever. It suffers from two things over time. It does tend to "dry out", but it also suffers from "pump out". As the parts heat cycle and expand and contract, the paste gets pushed out sideways over time. So - refreshing the paste can actually be good. I tend to advocate good quality stuff, like the Thermal Grizzly brand, as it is available to consumers. If you were a manufacturer of electronics, you'd have catalogs of thermal paste to choose from with all kinds of specs, but as a consumer, what are you going to do with 55-gallons of thermal paste?

But - the capacitors also produce some heat. These boosting power supplies operate at high frequency, like 80khz-100khz. They create a lot of ripple current in the capacitors, which becomes heat inside the capacitor as it dissipates the ripple current. That heat creates a rise over ambient temperature and that factors into the useful life of the capacitor.

Most of these types of capacitors age slowly. They lose some of their capacitance value, and they increase in internal resistance (which increases heat generated). So the circuits they are in tend to lose performance and stability over time. Good engineers actually design for this, but eventually, the capacitor will simply cease to do its job and the circuit just doesn't work right anymore.

That being said - who knows what is failing, but the caps are a good guess.

Wayne Smith

I'm a fan of avoiding heat but my problem (the same as others have described here) has never occurred while heat is building up during use but instead after a very brief power off cool down and then a restart.

Of course you might argue that at power off the fan shuts off and residual heat builds up in the components (and thermal paste or a good gap pad would help to resolve this).

That being said I have also had a couple occasions when the failure was at start up after the car sat overnight and everything was cold.

I've also had several occasions where all that was necessary to get things working again was a few minutes of ignition off and another restart (see next paragraph). I've never been able to fix it with a 15 second ignition off on cycle.

I discovered a 5 amp parasitic draw on my car a few days ago that lasts for a bit before dropping to just over an amp with an eventual drop to milliamps. So I'm not sure how long it takes the amp to shut off after the ignition shuts off.

That doesn't preclude the power supply or caps (especially any caps associated with a reset circuit). But I'm still inclined to worry about a CAN Bus comm problem or something in the reset circuit (similar to a problem I'm having in my F250 where it is definitely bus related at start up).

At least for me, this has been a very intermittent problem and as we know, those are the hardest to solve.

larrysb

Yeah, who knows what is failing, and it could be people are chasing multiple different issues. (and this is all about the 997.2 Bose PCM system...)

If you get the issue of the subwoofer is making sound, but the rest of the speakers are not, then the DSP section of the amp is working, and it is getting signal from the optical bus and it thinks the DC-DC converter and power amps are on.

That tends to say that the DC-DC power converter that powers the amp chips isn't working. It gets +12 all the time, and the DSP processor in the amp box is what tells it to power up. If it fails to do so, then we consider why that might be. Since the DSP is running, then the amp chassis is getting power, it is getting signal from the head unit, and it is reasonable to presume the DSP has signaled the power amp to turn on. (the subwoofer being on confirms this...).

If all the channels are out, that says the DC-DC power section isn't coming up. Could be a lot of stuff, but capacitors - likely suspect.

Like I've said, they degrade and the circuit gets more marginal and stops working reliably.

Wayne Smith

As pointed out, at this age we could be looking at multiple different problems. My woofer powers up but to hear it requires high volume and then it is more of a hum with no audio quality of any sort.

Fortunately it is a rare occurrence and so far has self healed each time.

AmericanPupusa

I have the same thing happening to me. I drove for about 40 minutes, turned the car off with the radio still on while I waited for a food order. When I turned the car on, the speakers all went slient with the exception of the woofer. All I could here was bass.