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radio suppressor relay 700 1986

posted by  Don Foster on  Tue Jan 6 23:39 CST 2004
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last visit: Sun Oct 5 11:53 CST 2014
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The so-called "radio suppression relay" controls power to the fuel injectors. If the relay becomes troublesome, it can intermittently disable the fuel injectors (this happened to my '91 740 -- resoldering completely solved the problem).

It's called "radio suppression" because by using a relay to remotely control the injector power, it suppresses RF interference from reaching the radio. Injectors (and switching their power) causes considerable electronic noise on the power line, and Volvo decided to keep that noise under the hood rather than bring it into the passenger compartment on the wiring harness.

"...and it will at times get engine noise through the radio..."

Most likely this is ignition noise, not electrical switching noise from the injectors.
--
Don Foster (near Cape Cod, MA)






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New radio suppressor relay [700][1986]
posted by  jackart  on Tue Jan 6 17:07 CST 2004 >


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