Tach doesn't work ECU burnt...

[USRB25S13]

My tach have never worked since I did my swap into my S13. The engine is a 95.5 RB25DET. When I first got the clip I took the ECU out and I noticed a "hot burnt" smell coming form the ECU. (no smoke or anything) Since the engine ran fine I didn't think much of it till I finished the swap and found out tach wouldn't work. I checked my wiring to make sure that was right. I then checked for a signal from the ECU and got nothing (No AC/DC or Hz signal) I then opened the ECU and found a burnt part on the circuit board.....the car drives ok but just no tach.

I have located and purchased a used ECU and before I hook it up I want to check and make sure my tach isn't shorted so I don't burn my new ECU. Does anyone know what a normal tach should measure for resistance? I plan to physically move the tach through it's full range to make sure it doesn't show low resistance to ground or power at any point. Is this a comman problem for them to just burn up for no resound?

[BigDatto]

Hi USRB,

Did you check this thread ? http://www.skylinesaustralia.com/forums/sh...ead.php?t=22535

Maybe your tacho is drawing too much voltage/current. I have no first-hand experience, but drawing 12v from an 8v rail could explain the carbon & freon smells from your ECU.

hope you sort it soon !

[USRB25S13]

I tested my tach. I saw 8v with the wire unhooked from the ECU. I grounded the wire and it moved. So I put my new ECU in and it works now! I am soo excited. After driving a month without a tach. lol

I put an inline a 1 amp fuse in the wire just to be safe.

[rsx84]

i've just put in a autometer 5" tacho and seem to have the same problem its ither there not enough power going to the tacho or i've cut the wrong wire on the tacho or there is no tacho pulse from the ecu ??

what it does is just sit on 3000 rpm and not move, when i remove the wire from the ecu it goes back to zero, the instructions said to cut the brown wire loop which i did???? any ideas

[BigDatto]

I tested my tach. I saw 8v with the wire unhooked from the ECU. I grounded the wire and it moved. So I put my new ECU in and it works now! I am soo excited. After driving a month without a tach. lol  

I put an inline a 1 amp fuse in the wire just to be safe.

Cool !

You kicked that one squaw in the nootz !:kick:

[rsx84]

I tested my tach. I saw 8v with the wire unhooked from the ECU. I grounded the wire and it moved. So I put my new ECU in and it works now! I am soo excited. After driving a month without a tach. lol  

I put an inline a 1 amp fuse in the wire just to be safe.

so it was your ecu that was the problem then!

[USRB25S13]

Yes My ECU wasn't putting out a signal. I think when I was wiring the insturment cluster into my car I put ing power to the circuit going to my ECU. BTW the car feels better with the new ECU.