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sprinkles08
sprinkles08, ASE Certified Technician
Category: Mazda
Satisfied Customers: 21604
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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I have 2007 cx-7 grand touring with nav pkg. radio head unit

Customer Question

I have 2007 cx-7 grand touring with nav pkg. radio head unit works fine but the sound only works in the middle of hot summer. do I need new head unit or bose amp or both?
Submitted: 1 year ago.
Category: Mazda
Customer: replied 1 year ago.
Is there a simple way to check if the culprit is the bose amp?
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to JustAnswer!

If the radio appears to operate normally yet there is no sound then you almost surely have an internal failure in the amp. It's possible that it could be the radio or a loss of power or ground to the amp but it's more likely to be the amp.

A scan tool would normally be used in diagnosis but I'm assuming one with the capability isn't available. The best thing to do would be to test the amp powers and grounds, and a test speaker could be used to test the audio inputs to the amp. The speaker output circuits can also be tested for a short to power or ground. If all is ok then the amp can be condemned.

Customer: replied 1 year ago.
I located the amp(EG2366920) and it has three groups of connectors. do you know the labels on the pins? I am assuming they are preamp inputs, amped outputs to speakers and power to the amp. can i try to use a multi-meter to ascertain if the amp is the culprit?
Customer: replied 1 year ago.
Also, do you have any opinion on the fact that sound only works when the weather is hot .. as in above 85F?
Expert:  sprinkles08 replied 1 year ago.

Do you have the VIN?

Customer: replied 1 year ago.
JM3ER29L070139907
Expert:  sprinkles08 replied 1 year ago.

Do you have navigation?

Customer: replied 1 year ago.
with bose system
Expert:  sprinkles08 replied 1 year ago.

Thanks, I'll get back to you as quickly as I can!

Expert:  sprinkles08 replied 1 year ago.

At the amp connector you should have battery voltage on the orange/blue wire, ground is black/blue. Are these present?

Customer: replied 1 year ago.
i don't have the car with me today. Ill try to find out tonite.
Expert:  sprinkles08 replied 1 year ago.

Ok.

Customer: replied 1 year ago.
Orange/Blue and Black/Blue are present. and they read 25v on the amp connector. strange enough, even if the radio is turned off. Can you provide me info (color)on one of the speaker channels on the preamp connector. if I am able to read the preamp reading, I think I can say the culprit is the amp itself rather than the head unit. I will need to strip part of the wire since holes in the preamp connector is too small for the meter probe. also I need the negative. (do i read against Black/Blue wire?) what voltage reading should I be looking for ?
Expert:  sprinkles08 replied 1 year ago.

It would be best to use a T pin or straightened paperclip to touch the terminals in the connector rather than stripping wires.

What did you test the power and ground with?

Customer: replied 1 year ago.
I used my multi meter. W orig tip
Customer: replied 1 year ago.
Do u have info on preamp input colors?
Expert:  sprinkles08 replied 1 year ago.

What did you have the meter set on?

Customer: replied 1 year ago.
as. you may have guessed i was using Vac setting n not Vdc( after doing some googling) . ill remeasure in the morning.
Customer: replied 1 year ago.
Orange/blue to black/blue is reading 12.6v.
Expert:  sprinkles08 replied 1 year ago.

Ok great.

With the amp connectors unplugged are there any circuits shorted to ground?

Customer: replied 1 year ago.
huh? if you mean there's any unintended connection to the ground, no these is none.
Expert:  sprinkles08 replied 1 year ago.

Do you have a test speaker?

Customer: replied 1 year ago.
No
Expert:  sprinkles08 replied 1 year ago.

The last thing that would need to be done then is test continuity of the speaker output circuits from the radio to the amp and from the amp to the speakers. It's highly unlikely that all circuits would go open at one time but you can check if you want. I can give the wire colors if you'd like but I am away from my service information until this evening.

Customer: replied 1 year ago.
wire colors would be most helpful. I am assuming to measure in Vac setting on the multimeter. Isn't it safe to assume if I can get preamp voltage on the connector with radio turned on then I can rule out bad head unit ?
Expert:  sprinkles08 replied 1 year ago.

Automotive applications are DC voltage but you won't be testing voltage. You'll be testing continuity between the radio and amp and then the amp and speakers if you wish.

Customer: replied 1 year ago.
Ok
Expert:  sprinkles08 replied 1 year ago.

I'll get back to you as quickly as I can!

Expert:  sprinkles08 replied 1 year ago.

Rather than checking continuity of each speaker wire you can test them at the amp connector and just read resistance through the speaker. These are the speaker circuits.

white/red in pin 2d, gray/red in 2f

white/red 2b, gray/red 2a

white 2k , gray 2m

white/violet 2c, gray/white 2e

white/violet 2i, gray/white 2g

white/violet 2h, gray/white 2j

white 2l, gray 2n

The only wires that go directly between the amp and radio are the white/black, gray/black, white/red and gray/red.

Customer: replied 1 year ago.
whats 2 followed by numbers mean n how am using them to test if the amp is good or not?
Customer: replied 1 year ago.
an example will be very helpful ... in detail please
Expert:  sprinkles08 replied 1 year ago.

Those are the pin location numbers in the connectors. You need to check continuity on the wires from the amp to the radio, test the continuity of the speaker circuits between each of the two wires I mentioned.

It's highly unlikely that you had this many speaker circuits damaged at one time. If the powers and grounds to the amp are good and there is no sound then there is little chance the problem isn't in the amp.

Customer: replied 1 year ago.
I do agree that there's any problem with speakers becAuse sound works on hot days. Also true is that connecting wires btwn head unit n amp is ok. Is there any way possible to check preamp input voltage(?) on the preamp connector to the amp?
Customer: replied 1 year ago.
On 4 wires u mentioned that go btwn radio n amp?
Expert:  sprinkles08 replied 1 year ago.

Yes, you'll want to test the four wires from the radio to the amp. If ok then the problem is the radio or the amp.

Customer: replied 1 year ago.
Great. I am assuming those r 4 channel preamp outputs from the radio. Now do I test them individually against the ground wire (black/blue) on the amp power connector?
Expert:  sprinkles08 replied 1 year ago.

You need to test continuity. The meter will be set to the 200 ohm scale, one meter lead at the radio connector and the other at the amp connector.

Customer: replied 1 year ago.
i am testing whether the wiring btwn radio n amp is good? rather than testing whether radio is putting out preamp signal to the amp?
Customer: replied 1 year ago.
Nevr mind. I got hold of cx7 workshop manual. Thanks for your input.
Expert:  sprinkles08 replied 1 year ago.

You're welcome!

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