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Technicaldan
Technicaldan, UK Car Mechanic
Category: UK Car
Satisfied Customers: 104
Experience:  Accredited
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My speedometer and oil temperature gauge doesant work. Fuse

Customer Question

My speedometer and oil temperature gauge doesant work. Fuse # ***** and #7 blows when egnition turns on. These circuits goes to the VSS and oil temperature sensor +++. I have changed both sensors and checked wiring. I have also measured resistance in wiring(00.7ohms in both) but still both fuses blow. I suspect there is an earth fault in one of these cuircits that triggers both to blow. How can i find out where the fault is?
Submitted: 5 months ago.
Category: UK Car
Customer: replied 5 months ago.
Fuse # ***** goes to:
- K142 Control lamp gear shifter
- M16 Left taillight
- M17 Right Taillight
-G22 VSS(automatic transmission)
-N18 Gas Throttle
Customer: replied 5 months ago.
Fuse # *****
- G65 Air condtition compressor
-J131 Heating driver seat
-J132 Heating passenger seat
-J255 Climatronic
-G266 Oil level/temperature sensor
-N147 Two way valve for cooling fluid
-V154 Stallmotor for airconditioning/ air circulation valve
Customer: replied 5 months ago.
Fuse 7= 10A
Fuse 5= 7,5A
Expert:  Ron replied 5 months ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

If bot sensor are not defective then you have to be dealing with a short to ground. I would start with rechecking the power feed wire to the VSS (black/green) for a short to ground. I have enclosed the wiring diagram in the link below for reference. Copy and paste the link to your browser to open and view it.

https://dl.dropboxusercontent.com/u/104923897/VSS%20wiring%20Jun%2014.pdf

Customer: replied 5 months ago.
Hi, thank you for your reply. As i mentioned earlier i have measured resistance in both Black/Green(Fuse 7) and Black/Darkblue(fuse 5). Both of these were 0.7ohms. If there were a shortage here they would show much higher resistance.
Any other ideas?
Expert:  Ron replied 5 months ago.

These circuit and or the components to them have to be shorted to ground or the fuse would hold. What happens if you unplug both new sensors? Do the fuses still blow?

Customer: replied 5 months ago.
Hi, Yes they do, so it has to be something else that is is shorted. I just changes and measured the sensors because i thought that was the easiest way to start. I was hoping that maybe you could tell me what component that was most likely to cause the fuses to blow since it seems that they are connected somehow. Its a big and almost impossible job finding and measuring all of the components/wires in both of these circuits.
Customer: replied 5 months ago.
I can mention that i have also cleaned off all main earth points that i have found while troubleshooting.
Expert:  Ron replied 5 months ago.

Unfortunately this is all the information I have on this, I will open the post back up for you and perhaps someone else may have something new to add. If they can help, they will respond.

Customer: replied 5 months ago.
Okay, thank you for giving it a shot. Have a nice day :)
Expert:  Technicaldan replied 5 months ago.

If you've measured the continuity of the wiring from end to end, that would not take into account for a short to earth, all that shows is current can make if from one end of the wire to the other.

A short to earth, that hasn't broken the wire would not increase the end to end resistance.

Try measuring the resistance from the wires to earth, it should be infinite, if not then there is a short somewhere.

Customer: replied 5 months ago.
Thank you for your tip, i have measured what i could trace on these two circuits and i can't find anything that points out. I can't say that im 100% sure that i found every wire that leads to these two circuits because it is difficult to follow/find everything from the cluster. I think its strange that two independant circuits short out at the same time so im thinking maybe its the ECU or something that connects these two is making a mess for me. I was hoping that maybe you guys had some diagrams that could show a possible connection between these two and maybe narrow the search down for me.

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