My car has started making an intermittent buzz noise from the under the dash area. Any ideas what it could be? I have removed all of the panel work but the noise seems to go away when I can look for it. The air-conditioner etc. is off and it still happens. Only when the car is running. I thought it might be a dying relay?
Is it intermittent, or only when the car is in motion? Is it independent of smooth / rough roads? I was thinking of a dead / cracked speaker cone in the factory warning speaker behind the dash, but that may not be consistent with occurrence.
It can happen when the engine is running and the car is stopped. It can happen on smooth or rough roads. It is intermittent. The only consistent thing is that the engine is running when it happens, so far anyway....
There is the flap that diverts air from the different vents on our 93+ Z's. Worn gearing or a wire shorting out may cause the buss from behind the centre panel of the dash. Other than that, the clutch booster can make more of a squeaking / hissing noise if it's on its way out. Unless its coming from the passenger footwell, or the fuse compartment in the drivers footwell, I would not think that its a relay on the blink. It's not from your tacho or shift light is it?
At the same time as I was blissfully unaware that my Rear U/C arms were disintegrating, we were also experiencing a mysterious rhythmic buzz that sounded as though it was coming through the speakers. My wife was convinced that it was coming from the drivers side of the cabin, and I was equally certain that it was from the passenger side. So, after checking all the stereo wiring and speakers(without success)I switched off the stereo system to halt the annoyance. Eek! It's still there. Hang on, it's coming from the roof.....you guessed it, it was the bloody miniature fan in the overhead Map Light console. 15 minutes later(after re-adjusting the bearings on said fan)no more noise(except for the constant "I told you so" from a soon to be former passenger):zlove:.
Problem fixed here is a solution As I originally suspected it was a faulty relay causing the buzz noise from under the dash. The specific relay in this case plugs into the back of the fuse block near the accelerator pedal and is called the "bulb check relay" it powers the "stop and tail" check light on the dash. The only clue that led me to this relay was that sometimes the "stop and tail" check light would flicker when the buzz noise started. Wiring diagrams and locations of the bulb check relay for a 2+0 can be found on pages EL-45, EL-46, EL-145, EL-158 and EL-159 of the maintenance manual. There are six relays that plug into the back of the fuse block. The bulb check relay is located on the top row and closest to the back of the car on a RHD vehicle (the maintenance manual is for a LHD vehicle in my case). This is a difficult relay to change and requires that the accelerator pedal is partly removed so you can partly remove the fuse block and most of its plugs. The bulb check relay can be removed buy firmly pulling it out, there are no clips holding it in. It is smaller than any other relays I have seen on the zed and has no part number on it. After doing a bit of research I have decided to leave the bulb check relay out. I also believe it was causing extra electrical load during failure as the alternator belt would sometimes slip a little when the buzz stopped (this might have been an effect rather than a cause of the belt slip). One guy on TT net blamed a whole range of problems on a faulty bulb check relay including: HICAS, brake, and the 'tail light out' warning lights randomly lighting up. Idle problem - high idle coming to a stop with a slow settle A/C - compressor clutch not working normally Warm start problem Safety boost - car stuck in safety boost HICAS - not working properly http://www.twinturbo.net/nissan/300z...---solved.html
Good to hear you got to the bottom of it mate. It really was a weird sound when you came over and we looked at it. Could you Rig up another relay, either nissan or off the shelf DSE type? Or will running without it be the plan for now?
You could rig up another relay if you wanted but that would probably make it more unreliable. I think it is easier to leave the relay out (like me) because of the difficulty in changing it and possible electrical issues it causes. Using LEDS in the tail lights is probably not a bad idea with the relay removed.
