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Electronics question


YSR_Racer_99

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Working on the SV1K. Getting rid of a bunch of the stock wiring/ cluster, etc. Instructions called for a .5w 100 ohm resistor, but all I had was a 1w 100 ohm. Okay to substitute? This is to keep the cluster from throwing a code, I believe (which is funny, cuz like I said, I got rid of the cluster..). Had it set up this way on the 650 as far as the wiring. wattage is the only difference, and now the fuel system won't prime/ pressurize.

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This resistor may cause an issue with the code being thrown, but I think you have another issue with the fuel pump. One of the troubles you run into when you deviate from stock is you really, REALLY, have to know your shit with some systems. Some systems have a failsafe, some don't, some work with a code, some don't. It's tough to say... we'd run into stuff like this a lot at Nissan and the more complex the vehicle, the bigger issues minor changes would cause. Sorry, I don't think that answered the question...

Go to Radio Shack and get the correct resistor. Or find different directions?

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LOL. Same directions worked fine on the 650, and the 1K DID start/ run/ etc just fine until....

Well. I don't know. Messed with a few things between it starting, then trying to start it again.

I guess my question is really about the .5w vs. 1w rating on the resistor. Its still the same resistance being read by the ECM, so shouldn't matter. Is that correct? I hate electronics...

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I really don't see why not. From a quick google it looks like the wattage rating is a function of heat dissipation vs. internals, or how much heat resistance the resistor can take before it burns itself out. With .5W difference, I don't think that's a huge deal.

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You are fine. You are using the same resistance, which is what is important. If it was a higher voltage/amperage system then it would require a larger Watt resistor, but since these are electronic components you can get away with low watt (read: cheaper) resistors. The code that gets thrown might cause the ECU to go into a "limp mode" where the map is tweaked for less power. If you are following a tutorial, I would follow it to the T without knowing the system well.

What were the last things you changed since the fuel pump stopped working. And stupid question, but is it wired up (you said you were doing a lot of re-work, sometimes things slip by when putting it back together)

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Agreed with above. 100 Ohm is the magic number. Keep that the same and things are good. A .5 watt resister can only dissipate .5 watts worth of heat. The 1 watt can dissipate more heat without damage. It will physically be larger to deal with the extra power and the wire leads will most likely be thicker. In the case of the wattage always use the spec part or one higher, but never go the other way as it may overheat and burn out.

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Figured it out. The resistor itself is bad. No conductivity through it at all. The key switch in the SVs has a 100ohm .5w resistor in it to help prevent hotwiring theft. If the ECU/ ECM doesn't see the (reduced voltage??) coming in from that line in the keyswitch module, it won't activate the fuel pump. So yeah, the resistor is necessary, and nothing was passing through mine anyhow.

Thanks to all for the input.

Soooo relieved that that is all it was. Only four more months or so til I can take it out and shake it down.

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