LadyKenai

hello again,

im trying to fix this issue, the radio in the jeep is a bluapunkt rpd 440 not an old stock model. when im listening to a station on AM i get a lot of interference over the speakers from wipers and blinkers i can hear the relays clicking over the speakers this gets even worse when the engine is running and goes to an higher RPM.
the speaker wires are good no kinks. i read somewhere to run a seperate ground wire from the radio to the battery so ive tried this but the interference is still the same even a bit worse. all the ground points in the engine bay and cab area are refreshed. when having the engine off and nothing else on but the radio everything sounds clear front right left back all good.
what would be the issue here ?..

thanks , marc

CCKen

Does the Grand Cherokee have a bonding strap going from the firewall to the cylinder head bolt, like in the pic below?


Pic is of an XJ Cherokee bonding strap. As you can see in the pic it's for radio noise suppression.



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LadyKenai

sorry yes i am talking about the xj 88 renix and i do have that breaded cable.
last summer i went through cruiser54 tips on grounds and i have refreshed all those
the ground wires (brushed clean to clear metal and removed oil gunk) you are taking about i have scrapped the metal clean on the firewall and reattached it. with my multimeter on ohms and that exact scrapped part to the negative of the battery i get 0.03 ohm i think that is good?

now the other end of this breaded cable i did not take lose cause it is attached underneath one of the studs on the cylinder head and i didnt want to mess wit the torque specs since i dont have a torque wrench but its on there tight and looks good

thanks

BlueRidgeMark

Kudos, Marc, you have done all the right first steps!

I'd still suspect that braided strap, though. It's cheap to replace, and though you've cleaned up the mounting point, the problem may be the strap itself.

Since you are getting it from multiple sources, the problem probably is most likely a systemic problem like a bad ground, hence the suspicion about that ground strap.

However, it's also possible that that particular radio is just sensitive to noise. If that is the case, you'll need to attack it in several ways, but I'd still start with that braided strap.

If the problem persists after that, another thing you can try is to install a capacitor between the power and ground leads on the radio, close to the radio itself. I'd put it right behind (on the vehicle side) of where the radio plugs into the car's harness.

You don't need one of those monsters that audio buffs like to install on their amplifiers. Something in the under $5 range is plenty.

LadyKenai

thank you for your reply,

what gauge should i replace the cable with ?

CCKen

You can use a Dorman bonding strap. See pic.



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BlueRidgeMark

Yep. It doesn't need a huge fat cable, just a good one like Ken showed. It's not intended to carry a lot of current. That braid is actually better for this purpose than a #1 welding cable.

LadyKenai

ok this is what i found at oreilly's

http://www.oreillyauto.com/site/c/de...1558&ppt=C0005

something like that ?

if this is the right cable what about the old one, do i leave it attached and just double this one up ?
i see also a new contact point at the fuel rail instead of the engine stud, perhaps i can just cut the old wire at the engine stud and leave that untouched and remove the rest ?

i sure hope this will fix it that would be nice its so annoying to listen to that noise.

CCKen

I wonder what size holes are in the ring terminals on that piece you linked.


That Dorman strap I posted has the small hole for the fuel rail hold down bolt, and the large hole for the firewall.

CCKen

I did read in the 1990 FSM about eliminating static from the turn signals, etc., using a capacitor like BlueRidgeMark mentioned. If the new bonding strap does help I can post up some pages from the '90 FSM that talks about these things.

LadyKenai

ok, i have to see it up close at the store.

i will update in here about the results..

CCKen

Don't be afraid of removing that bonding strap nut on that cylinder hold down bolt. Apply some penetrating oil then remove the bonding strap nut with a box end wrench. That cylinder head bolt is torqued in at 110 ft/lbs so it ain't going anywhere. Lots of penetrating oil BTW.

Here's a pic of what I did to my old strap before going with the new smaller strap.



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The reason I went with that new smaller strap is that I cut off the threaded portion of that hold down bolt so I could get a shallow socket on it when I replaced my cylinder head and therefore could not reuse the original strap.



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BlueRidgeMark

That would be perfect!

LadyKenai

ok back home, installed the new braided cable the interference remains, the holes in the cable were just right one was a little bigger for the bolt on the firewall and the other end a little smaller eye, just right. i want to say the interference is a bit less but still quite strong. a capacitor of what range/value am i looking at, i asume this will be installed in the lead wire of the radio not the ground ? marc

[edit] i just read it again, the capacitor will be installed from the lead wire to the ground wire closest to the radio

ive tried uploading a picture of the braided strap but didnt work, it is in fact the one i posted earlier for 6$

LadyKenai

here is a picture of the wiring on the back of the radio, i do know and you will see the two orange wires coming together leading into one and then stops.. i have an idea this is the wire for the display since the display worked before but cant find the other end that seemed snapped off if that else the display is just broke not sure.