Radio Capacitors
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Cross-Country
Joined: Nov 2014
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Radio Capacitors
'97 E150 with 5.4 liter
My radio, which until recently was silent, now has a bit of noise to it. I'm looking at the capacitors. Are those only for quieting the radio or do they also serve to suppress RFI to the engine control module?
I understand that if they short the engine will not run, but if they fail open will it result in anything but a noisy radio?
BTW: Why are they so darn expensive? It's just a small capacitor with a wire and connector. $30 each, really?!!!
My radio, which until recently was silent, now has a bit of noise to it. I'm looking at the capacitors. Are those only for quieting the radio or do they also serve to suppress RFI to the engine control module?
I understand that if they short the engine will not run, but if they fail open will it result in anything but a noisy radio?
BTW: Why are they so darn expensive? It's just a small capacitor with a wire and connector. $30 each, really?!!!
Laughing Gas
Joined: Feb 2005
Posts: 786
Likes: 26
He's probably referring to Radio Shack. I think they are gone. They sold their stores to Sprint, and have a few outlets in HobbyTown, but I don't think they exist otherwise.
If they are just for radio noise suppression, the value isn't really critical. Just get in the ballpark. Are there any markings on them?
If they are just for radio noise suppression, the value isn't really critical. Just get in the ballpark. Are there any markings on them?
Fleet Owner
Joined: Aug 2010
Posts: 21,255
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From: Reynoldsburg, Ohio
If I were looking for an RFI suppressor I'd check with a car audio shop, locally or online. Crutchfield or eBay would be my online choices.
Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
Radio Shack went bankrupt several years ago. They still have an online presence and the brand still exists to support small network of franchised dealers only. They did not sell their stores to Sprint, that was a last gasp effort to maintain some sort of retail B &M existence before they finally pulled the plug on corporate stores.
Going back to the original post...
The RFI caps are there to suppress ignition noise. If they fail open, the engine will radiate electrical impulse noise while running that can interfere with multiple things, the most obvious would be the vehicle's own radio. The noise will be particularly pronounced on AM radio. Just be aware that a noisy AM radio can have multiple causes, this is only one of them.
Going back to the original post...
My radio, which until recently was silent, now has a bit of noise to it. I'm looking at the capacitors. Are those only for quieting the radio or do they also serve to suppress RFI to the engine control module?
I understand that if they short the engine will not run, but if they fail open will it result in anything but a noisy radio?
I understand that if they short the engine will not run, but if they fail open will it result in anything but a noisy radio?
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Cross-Country
Joined: Nov 2014
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Could be that the increased noise is the result of the new alternator. Sounds more like alternator whine than spark plug noise.
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Laughing Gas
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https://duckduckgo.com/?q=radio+shac...=v171-1&ia=web
Hotshot
Joined: Jan 2004
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From: St Louis
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Cross-Country
Joined: Nov 2014
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Amazingly enough, there is still an electronic parts supplier in Knoxville. Shields makes most of their money from networking supplies and installations, but they still have a store selling components.
BTW: I had the rear cover off the engine today so I got out my capacitance meter. Both my caps measure 390 pF. Don't know if this is correct, but they both measure the same.
Laughing Gas
Joined: Feb 2005
Posts: 786
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Yes, it's very good, but you do have to know what you want. Does he need tantalum or electrolytic? Or maybe ceramic? Polarized? Or not? Axial? Pass through? What size? Well, it looks like we've already covered that, but what are the tolerances? Can he use one half the size? Twice the size?
There are a LOT of questions to be answered, and someone who is not well versed in the subject is going to be lost in that site.
For myself, I'm glad you posted it, because I had not known of them before and I will find it useful. But it's a bit much for someone who just needs a radio suppressor.
There are a LOT of questions to be answered, and someone who is not well versed in the subject is going to be lost in that site.
For myself, I'm glad you posted it, because I had not known of them before and I will find it useful. But it's a bit much for someone who just needs a radio suppressor.
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