[JMB36TA]

I posted this in the electrical section and haven't been getting any responses so I hope someone here can help.

Here's my issue. I bought a cheap Bosch tack to use to tune my fresh rebuilt 400 for my 69 bird. I needed something to set the timing and idle and didn't plan on installing it permanently in the car. I temporarily installed it during the break in to keep an eye on things but the wire from the distributor is interfering with my radio. With the tach hooked up and the car running the radio buttons sometimes don't work, it won't turn off with the power button and sometimes when I turn the car off, the volume knob don't work, the presets get screwed, and sometimes the speakers don't work. I unplug the wire from the distributor and the radio goes back to normal. I plug it in and it goes haywire again. The problem only happens with the car running, it's fine with the ignition in the on position and the car not running. I talked to the radio manufacturer and they suggested putting noise suppressing magnets on the distributor wire (I forget what they're called) so I got some and put 4 on. It helped but there were still issues with the radio. Then they suggested rerouting the wire so I tested it by running it through the driver side window but that didn't help either. It was originally routed through the firewall and behind the radio. I disconnected the tach and now my speakers turn off for a split second and makes the radio sound like a record skipping. I think it's permanently damaged. Retrosound is sending me a new radio body under warranty but I want to keep a tach in the car. I'm looking at a Stewart Warner tach to match my other gauges but don't know if I want to spend the $125 and possibly ruin another radio. I know this has to work somehow, anybody else ever have this issue in their car?

[steve25]

I do not think that your HEI or Tack is the issue I think that by coincidence your radio took a big static discharge hit that damaged it at the same time you where doing the Tack install!

[JMB36TA]

Originally Posted by steve25

I do not think that your HEI or Tack is the issue I think that by coincidence your radio took a big static discharge hit that damaged it at the same time you where doing the Tack install!

If I disconnect the tach wire from the distributor the radio worked fine. When I plugged the wire back in, the radio went haywire again. I tested it several times all with the same results. But I think it’s permanently damaged now. I’m no electrical scholar but if it took a big static discharge that damaged it, wouldn’t it be screwed up no matter if the tach was connected or disconnected?


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[lust4speed]

I'd check the grounds on the tach and radio --and also check dash ground to body and firewall to engine. Sounds like you might be getting voltage back-feeding into the radio that should be completing its circuit to ground.

[leeklm]

Originally Posted by lust4speed

I'd check the grounds on the tach and radio --and also check dash ground to body and firewall to engine. Sounds like you might be getting voltage back-feeding into the radio that should be completing its circuit to ground.

This^^^ I do not think you can have too many ground straps to the chassis, engine, etc. A bad ground can give you some really crazy symptoms!

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[JMB36TA]

Originally Posted by lust4speed

I'd check the grounds on the tach and radio --and also check dash ground to body and firewall to engine. Sounds like you might be getting voltage back-feeding into the radio that should be completing its circuit to ground.

They were both mounted to the same bracket under the dash. I can try running the tach ground somewhere else.

[HWYSTR455]

What kind of radio?

.

["QUICK-SILVER"]

Originally Posted by HWYSTR455

What kind of radio?

.

Retrosound in first post and they are sending a replacement.

He didn't mention bluetooth or remote control info.

With failed/shorted components the thing might be a geiger counter now.

Clay

[JMB36TA]

Originally Posted by HWYSTR455

What kind of radio?

.

It's a Retrosound Rodando and it's less than a year old. It has bluetooth and USB ports.

[johnta1]

Where are you getting the power for the HEI?
And the radio?

I'd try a capacitor (noise suppressor) and see if that helps.

["QUICK-SILVER"]

Originally Posted by JMB36TA

It's a Retrosound Rodando and it's less than a year old. It has bluetooth and USB ports.

Did it ever work right? If it worked and then failed...Have you had any other problems; like over charging?

Found this from 2010 over on Team Camaro. Posting link for info and future reference. May or may not have any relevance to what's going on here.
https://www.camaros.net/forums/19-el...-problems.html

I'd say definately need to find out why the tach lead/coil (-) is turning in to a transmitting antenna when it's hooked up. Could just be a stray spark caused by a plug wire problem. Or maybe a coil ground problem. Either under the dust cap or where it screws down with the radio capacitor inside the distributor.

Going to need a good radio to figure out what's going on..If anything is.

Clay

[george kujanski]

Do not put additional capacitors on the tach wire. Make sure the radio is grounded to the dash metal well and the dash/firewall is connected well to the engine block. Route the tach wire away from the radio, in fact route it along the dash sheet metal.

George

[torqhead]

^^^ What George said, read carefully and do both items he mentions!

[rohrt]

I would be doing some troubleshooting by putting a meter on the Radio power leads. Read the DCV with the tach both on and off. Then read ACV the same way. Not as good as putting an O-scope on the line but may give you some clues as to what is going on.

[steve25]

This is a very strange issue because that wire only carrys a magnetly triggered pulse that has far less electrical radiation then for instance the spark plug wires themselves !
With the Tack wire unhooked to you hear any minor spark plug firing static in the radios output?

[JMB36TA]

Originally Posted by steve25

This is a very strange issue because that wire only carrys a magnetly triggered pulse that has far less electrical radiation then for instance the spark plug wires themselves !
With the Tack wire unhooked to you hear any minor spark plug firing static in the radios output?

None at all. The radio was perfect without the tach hooked up.

[george kujanski]

The tach wire has some nasty electrical transients on it with noise going up to hundreds of volts. Tach inputs suppress these transients but the wire itself can be a really good transmitter.

George

["QUICK-SILVER"]

Originally Posted by george kujanski

The tach wire has some nasty electrical transients on it with noise going up to hundreds of volts. Tach inputs suppress these transients but the wire itself can be a really good transmitter.

George

Would a shielded wire help with that? Using distributor ground and tach ground for the ends of the shield.

Clay

[torqhead]

Originally Posted by "QUICK-SILVER"

Would a shielded wire help with that? Using distributor ground and tach ground for the ends of the shield.

Clay

Interesting idea Clay, possibly would help. And you've known me long enough that I'm not bashing or discounting the idea but I gotta believe there's probably something basic going on here. Many of us use HEI hooked up tachs with decent stereo's and don't have this issue.

[george kujanski]

If the noise is radiated, the shielded cable may help. However, if the issue is a poor ground between the panel metal back to the engine ground it may not help.

The panel metal must have a good ground connection back to the engine ground. Without that, the tach noise current may mix with the radio power return injecting noise into the radio.

The 67 A body dash is a good example...the dash panel to dash/cowl metal connection is primarily thru a metal bracket that attaches the back of the panel metal to the column support. If the panel is ever removed, lazy mechanics either forget or disregard the bracket mounting bolt, eliminating this main ground path. Funny things begin to happen.

As a test, attach a good size wire between the radio metal chassis to a good dash/cowl metal to make sure the radio metal has a good ground path. If the problem goes away, the metal ground path needs improvement.

George