Hi, my car won't start this morning. After figuring out what was the problem, I switched the 2 relays in front of the coolant reservoir and the car started right away.My question is this: what are this 2 relays and how do I know w/c one is bad, since i switched them-left to right and right to left. Thanks guys for your input.By the way I have a 90 740 wagon 8 valve engine.

..you have got all the answers already, but just to share my experience:

I have ackuired my '90 745 less than a year ago, and it had this time-to-time no-start condition. Turned out to be one these relays. The old one says "Made in West Germany". The country which no longer exists... East plus West Germany reunion happened in 1990. Provided that these relays are made as good as before, one should expect at least 10 years life span for them.

If you're not sure which one is which, just leave one unplugged and try to start it and work it out that way. You won't harm the car.
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Ken
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'
Click here for the 700/900 FAQ

Yes they are identical. One is the "radio suppression relay". Not really radio, but provides power for the injectors. The other is for the electric cooling fan.
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Post Back. That's whats makes this forum work.

The part everyone leaves out is radio NOISE suppression relay. To keep the injector pulses from producing elecrical(radio) noise throughout the car's other or related circuits. I'm not sure which circuits, but that word would eliminate so many bouts of confusion...

Cheers
-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

Thanks guys for the input. God bless.