Radio Interferences with RPM and Blinkers

[Jorge Silva]

Hi guys,

 

So, I have recently tried to figure out a problem I have with the radio. This problem already existed before, and I am now focusing on that to have the car working 100% perfectly.

 

When I have the engine on, in whatever mode (AM FM Cassette) there is always an annoying interference according to the engine RPM. Higher RPM, higher interference volume. It sounds like a whistle.

 

Later, I found that that I have have interference when the blinkers are on.

 

When the engine is off, ignition on and blinkers off, the radio works perfect.

 

When the engine is off or on, ignition on and blinkers on, I can hear the flashing sound coming from the speakers.

 

I have tried the following without success so far:

1. Directly connect the radio to the battery. Didn't work, the interference noise remains unchanged as soon as I get the blinkers or engine working.

 

2. Checked all ground points, everything seemed OK and all the remaining electronics and lights in the car are working 100%.

 

3. Disconnected the alternator cables, didn't start the engine, but with ignition on, alternator off and blinkers on, the noise from the speakers remained.

 

I'm now out of options, i dont know what to do next. Are the interference noise from the engine rpm related to the blinkers? Could  it be a relay problem or something like that? Or could it be a faulty?

 

The car belonged to my grandpa, but he passed away 23 years ago. The sound set up system is exactly the same as before, no modifications were made, so I really doubt it was not working properly at the time. I remember this problem already existed some years ago when I took the car to the anual MOT.

 

Note: The noise only exists when the radio is ON, when it is OFF, there aren't any kind of interferences.

 

Many thanks.

 

 

Edited August 29, 2023 by Jorge Silva

[stephers]

Make sure that the body is well grounded to both the battery and the engine as well as between the battery and engine

You may also need what we used to call a "radio choke"      It was a noise suppressor that went between the radio and the + pos pick up         Does your alt have a little black box attached and wired into the back of the alt?  That is one noise suppressor 

 

There as also a ground cable kit that went between the hood and the main body of the car to help with noise suppression ( although, I am not so sure that this actually did anything )

 

Thanks, Rick

[tzei]

Interference comes from alt or ign.system. Check (again) radio’s earth.

 

About 5kOhms on every plug/wire should do. Also there are anti-noise gismos out there for few bucks.

[Son of Marty]

Are you running resistor wires or spark plugs? Is your ignition system stock? As above any electrical problems on a 02 the first step is to clean all grounds.

[Jorge Silva]

Thanks to all of you for the tips. I will give it a try again tomorrow.

 

Buy if it was a bad ground, would the noise remain with the radio ground directly connected to the battery? I mean, I did try to connect 2 separate wires straight from the battery to the radio but no changes. 

 

And yes, the alternator already has that little black box attached and wired.

 

The ignition is original, the car is most likely 100% original. I'm using spark plugs, replaced some months ago, also new spark plugs cables but none of these improved the interference noise.

 

Many thanks.

[John76]

51 minutes ago, Jorge Silva said:

new spark plugs cables

Jorge,

What type of spark plug cables are you using?

Do not use solid copper core wires. These cause radio interference.

As noted above by @Son of Marty, use resistor caps on the distributor and spark plugs, and use the carbon-core resistance spark plug wires.

Also check your antenna wire to make sure it is grounded properly to the radio.

[Son of Marty]

2 minutes ago, John76 said:

Also check your antenna wire to make sure it is grounded properly to the radio.

And to the body via the mounting screw.

[Jorge Silva]

18 hours ago, John76 said:

Jorge,

What type of spark plug cables are you using?

Do not use solid copper core wires. These cause radio interference.

As noted above by @Son of Marty, use resistor caps on the distributor and spark plugs, and use the carbon-core resistance spark plug wires.

Also check your antenna wire to make sure it is grounded properly to the radio.

 

Hi,

 

I do not understand much about spark plugs cables, but I took a photo of what I did installed. Before this new set, the car still had the original cables which were hard as a rock and cracked when I touched them.

 

Antenna is properly grounded, anyway I did run some tests without the antenna cable connected to the radio but no changes.

 

Thanks 

[Jorge Silva]

So today I did some more tests but without success. 😪

 

I cleaned all ground points again: inside the glove box, under the dash next to the heater box, also in the hood handler, from the engine to the firewall, relays, etc. Everything I could find doing ground connection I cleaned again, check the connections but all seemed to be in proper condition.

 

Voltage measured in the battery and between battery and other ground points was still the same: 12,56 Volts. The Ohms between the negative battery and other grounds in the car were maximum 3,2 Ohms, but the average was between 0,3 and 1,4 and at the radio ground cable it was around 1,2 Ohms.

 

I did find another interference cancelation device (small black box) connected to the coil.

 

I'm out of ideas now, i attach some pictures below and a video with the whistle noise when engine is running.

 

Many thanks.

 

[jimk]

The black boxes are capacitors.  A capacitor will let voltage spikes and alternating current leak to ground through it's mounting screw/bolt.  Where you found them is where they should be and except for cleaning their mounting and assuring they are grounded, they should be ok.

[ray_]

5 minutes ago, jimk said:

The black boxes are capacitors.  A capacitor will let voltage spikes and alternating current leak to ground through it's mounting screw/bolt.  Where you found them is where they should be and except for cleaning their mounting and assuring they are grounded, they should be ok.

Older capacitors would tend to leak over time. Not sure if those qualify as "older."

 

Cheers,

[visionaut]

It might be those plug wires...especially if that’s all you changed.

 

Class C wires are the lowest rated that still pass the SAE standard for High-Tension Ignition Cables (SAE J2031). Class E is the best. The classes relate to both the thermal handling and the EMI/RFI noise suppression capabilities of the wire…

[Son of Marty]

It looks like your Grand Pa was fighting this problem for a while, there's more sound suppression devices on your car than I've ever seen. The fact is does it while using the tape player IMO, and I'm not a radio guy, kinda rules out over the air transmission of the interference, do you have another radio you could try?

[tzei]

Or bench test that radio & speakers.

 

 

Oh and that left side of engine bay ”electrix” screams attention.

[Jorge Silva]

13 minutes ago, Son of Marty said:

It looks like your Grand Pa was fighting this problem for a while, there's more sound suppression devices on your car than I've ever seen. The fact is does it while using the tape player IMO, and I'm not a radio guy, kinda rules out over the air transmission of the interference, do you have another radio you could try?

 

The sound supression devices near the alternator wiring were all installed by myself some months ago as I did try to eliminate the noise with a cheap and quick fix, avoiding disassembly the center console, etc. I will try to move those devices to the radio wiring and see what happens. 

 

Something I noticed is that when I disconnected the radio from the car wiring and directly connected it with 2 independent wires to the car battery, the noise interference decreased its volume, didn't disappear but it got better.

 

I don't have another radio, but I will see if I can find one to try. If with another radio the interference doesn't dissappear I will try to focus on the plugs wiring.

 

Thanks to all of you.