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Another Noise question

D

Dodgeboy426

Member
Jun 20, 2006
11
0
11
Hi, been a lurker here for about a year, great site.

Now, the question:

We have a 2000 durango with an electric cooling fan. our RF noise level is unacceptable!

I bonded the hood and it's no better, and when the fan kicks in it makes the radio useless.

So, how do I filter the fan noise out? I've heard about putting a cap in the system but i'm not sure how to do this.

Thanks in advance, DB426
 

Use a capacitor of about 0.01 microfarads and install it directly across the wires going to the fan motor as close to the fan motor as you can. Just strip a bit of insulation off each lead and solder each leg of the capacitor to a wire. Polarity does not matter. Be sure to tape the connection well after. That should reduce the noise considerably.
 
You might also look at installing a heavy duty choke in the B+ lead (positive power lead), as close to the radio as reasonably possible. A lot depends on whether the noise is coming in via the power leads or via the antenna. You can always check this by disconnecting the antenna when the noise is present. If the noise disappears, it's obviously coming in via the antenna, and the choke won't be of much help.

Radio Shack used to sell such chokes, and I think some of them might still have a few lying around. If not, places that install aftermarket car stereos would be a good choice.

If you want to make your own, you can take 20 - 30 feet of #16 gauge wire and wrap it around a steel or ferrite core. I remember seeing one that was wrapped around a steel carabiner, and everyone who took the 10 minutes or so to make one of these seemed to be happy with the results.

As long as I'm making suggestions, since most of the noise caused by DC motors is due to worn/dirty brushes, it probably couldn't hurt to get a new set of brushes and to install them and get them properly seated. If the existing brushes are in good condition, look at the commutator for signs of wear.
 
Beetle said:
You might also look at installing a heavy duty choke in the B+ lead (positive power lead), as close to the radio as reasonably possible. A lot depends on whether the noise is coming in via the power leads or via the antenna. You can always check this by disconnecting the antenna when the noise is present. If the noise disappears, it's obviously coming in via the antenna, and the choke won't be of much help.

DB426-It is the antenna

Radio Shack used to sell such chokes, and I think some of them might still have a few lying around. If not, places that install aftermarket car stereos would be a good choice.

DB426-I already have one installed, still NFG

If you want to make your own, you can take 20 - 30 feet of #16 gauge wire and wrap it around a steel or ferrite core. I remember seeing one that was wrapped around a steel carabiner, and everyone who took the 10 minutes or so to make one of these seemed to be happy with the results.

As long as I'm making suggestions, since most of the noise caused by DC motors is due to worn/dirty brushes, it probably couldn't hurt to get a new set of brushes and to install them and get them properly seated. If the existing brushes are in good condition, look at the commutator for signs of wear.

DB426-The fan is a brand new aftermarket sealed unit
Click to expand...
 
QRN said:
Use a capacitor of about 0.01 microfarads and install it directly across the wires going to the fan motor as close to the fan motor as you can. Just strip a bit of insulation off each lead and solder each leg of the capacitor to a wire. Polarity does not matter. Be sure to tape the connection well after. That should reduce the noise considerably.
Click to expand...



Ok, I will try this out. I have a 0.01 mf Cap in my parts bin.

One question though, will the heat effect the cap? It gets ripping hot there. Also what about water?

Thanks everyone for the replies
 
Heat shouldn't affect a capacitor. I'd use a disc ceramic, and the actual value may not be all that critical. 0.01 uf is a good place to start, though. For voltage rating, don't use anything rated at less than 35 volts (and I'd go higher still). Most disc ceramics are rated at least 200 volts.

In my earlier post, I said that the noise filter in the B+ line might not work if the noise is coming in via the antenna. And you verified that.

It sounds like even "brand new aftermarket sealed units" can have problems. If you bought it locally, you might take it there and show them. They might offer you a replacement. Maybe not, but it couldn't hurt to ask.
 
dodgeboy

hook the radio stright to the battery

should cure your porb

we have a durango also and run a magnum s980 and have to run the noise blanker and have no probs

also what type of antenna are you useing
 
fatdude1 said:
dodgeboy

hook the radio stright to the battery- it is ;)

should cure your porb- Nope such luck :roll:

we have a durango also and run a magnum s980 and have to run the noise blanker and have no probs

also what type of antenna are you useing- 4'firestik on a fender mount :roll:
Click to expand...
 
WOW, uh......With that perfectly good roll bar there just waiting to be grounded to the frame and have a 8' Francis Amazer mounted up, whats with the fender mount?
Go with the strait to the battery idea, it should solve most of the bs, but with the antenna so close to the elect motor and in the same grounding field, you may benefit from the antenna relocation the most.
 
Running the radio power leads directly to the battery may not help much if the noise is being picked up by the antenna.If it was coming in on the power leads I would agree however. Try the cap on the fan leads first since it is relativly easy to do then see where you stand with the problem.
 
skirtchaser said:
WOW, uh......With that perfectly good roll bar there just waiting to be grounded to the frame and have a 8' Francis Amazer mounted up, whats with the fender mount?
Go with the strait to the battery idea, it should solve most of the bs, but with the antenna so close to the elect motor and in the same grounding field, you may benefit from the antenna relocation the most.
Click to expand...


the prob is with our Durango, not my Ram ;)

the Ram is awesome: 5' Wilson silverload on the rollbar and we get out like no tomorrow :LOL:
 
QRN said:
Running the radio power leads directly to the battery may not help much if the noise is being picked up by the antenna.If it was coming in on the power leads I would agree however. Try the cap on the fan leads first since it is relativly easy to do then see where you stand with the problem.
Click to expand...

like I said, the radio is straight to the battery, we have a noise filter on it as well. It is all engine RF coming through the antenna.

and the wife doesn't want me to drill a hole in the roof for a mount there so we have to stick with the fender mount :roll:
 

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