where can i get a quiet automotive relay?

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trevors

Copper - Posts: 86

Joined: April 14, 2008

Posted: July 31, 2009 at 9:20 PM / IP Logged

I just built and installed an intermittent wiper circuit for my rear, but although it's working correctly, the 30/85/86/etc relay I got from PepBoys (A2C Part# 775) is unpleasantly loud when it releases. It wouldn't be a problem for lock/unlock or engine start functions, but for intermittent wiper control, the noise occurs at the beginning of every wiper cycle and is impossible to ignore. I've tried wrapping it in heavy felt, but it made only a minor improvement.

I don't know if there are other manufacturer's 30/85/86/etc relays that are reasonably quiet (which would be preffered since that's the installed socket) or if I have to go to something else entirely, but if there's a much quieter SPST NO relay out there that doesn't cost a pile, I'd love to learn about it. (The rear wiper fuse is 15A.)

trevors

Copper - Posts: 86

Joined: April 14, 2008

Posted: July 31, 2009 at 9:22 PM / IP Logged

Car is 2008 xB, but I don't see that as germane to the question,

i am an idiot

Platinum - Posts: 13,670

This member consistently provides reliable information

Joined: September 21, 2006

Location: Louisiana, United States

Posted: July 31, 2009 at 9:26 PM / IP Logged

Turn your radio and amps off, do you still hear the noise? If the noise goes away with radio and amplifiers off, install a diode across the relay as depicted in the following link. Any 1 amp diode will do. Radio Shack will have one. https://www.the12volt.com/relays/page5.asp#ctm Disregard the diagram in the link. Only pay attention to the diode. The Banded end of the diode must attach to the positive wire.

Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB

91stt

Silver - Posts: 564

Joined: May 24, 2006

Location: New Jersey, United States

Posted: July 31, 2009 at 9:44 PM / IP Logged

try a solid state relay, no click at all.

check digikey.com to see what fits your application

trevors

Copper - Posts: 86

Joined: April 14, 2008

Posted: July 31, 2009 at 10:01 PM / IP Logged

i am an idiot wrote:

Yes, this is with the radio off -- it also did it during my bench testing before install, which is when I wrapped it with felt. I hoped it might actually be OK installed, but unfortunately no. The noise is specifically mechanical -- I can hear the spring vibrate. The engagement is a reasonably survivable click (mechanical again), but the release is just a bit much.

KPierson

Platinum - Posts: 3,527

Joined: April 14, 2005

Location: Ohio, United States

Posted: July 31, 2009 at 10:02 PM / IP Logged

How much current do you need? Reed relays and transistors are both silent. Depending on how much current you need one or the other should work.

Kevin Pierson

trevors

Copper - Posts: 86

Joined: April 14, 2008

Posted: July 31, 2009 at 10:13 PM / IP Logged

91stt wrote:

try a solid state relay, no click at all.

check digikey.com to see what fits your application

Thanks, but the highest SPST NO socketed solid state relay current capability I see there is 3A. A bit low for driving a motor with a 15A fuse.

trevors

Copper - Posts: 86

Joined: April 14, 2008

Posted: July 31, 2009 at 10:16 PM / IP Logged

trevors wrote:

91stt wrote:

try a solid state relay, no click at all.

check digikey.com to see what fits your application

Thanks, but the highest SPST NO socketed solid state relay current capability I see there is 3A. A bit low for driving a motor with a 15A fuse.

Oh yes, and the unit price is $43.52, think I'd better stick to mechanical.

trevors

Copper - Posts: 86

Joined: April 14, 2008

Posted: July 31, 2009 at 10:30 PM / IP Logged

KPierson wrote:

How much current do you need? Reed relays and transistors are both silent. Depending on how much current you need one or the other should work.

I don't know the actual current requirement, it's a motor fused at 15A. I imagine the current needs will tend to be higher on icy/snowy weather than at present. Yes, I could add a power transistor and another driver I suppose, but I'd prefer to avoid the heat and stability issues in driving high current, and a winter motor stall could be deadly. A mechanical relay is both a simpler and more reliable solution.

I'm not used to reed relays being high current capable, and wiper motor's can present unfriendly loads, but still, I'll take a look.

trevors

Copper - Posts: 86

Joined: April 14, 2008

Posted: July 31, 2009 at 10:36 PM / IP Logged

trevors wrote:

KPierson wrote:

How much current do you need? Reed relays and transistors are both silent. Depending on how much current you need one or the other should work.

I'm not used to reed relays being high current capable, and wiper motor's can present unfriendly loads, but still, I'll take a look.

I see 3A at the high end of the reed relay spectrum -- doesn't look good to me.

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