3N71B ELECTRICAL TROUBLE

[Datsun fan]

The CAR IS 510 AUTOMATIC , THE WIRING HARNESS IS NOT STOCK , all electrical things work

just fine (including gearbx inhibitor swicth,reverse light) and gearbox-to-intake hose

is connected well, Oil level and smell are good with no slipping.

The gear changing is pretty good except electrical kickdown is absent .

 

The switch under gas pedal does works perfect,then the wire goes to gearbox on driver side

"diaphragm",just before that "diaphragm" the power is good and just after exitting that

"diaphragm" the power becomes weaker :angry: (the 3 WATTs test bulb I use will become dim) then goes to passenger side wire (Black/yellow stripe as I remember) , IS THIS NORMAL ?????

The elec kickdown worked fine in the last 4 months . Is there possibility that there is

mechanical failure somewhere in the g/b ? How to diagnose ?

 

I Hope problems with those automatics will go away someday..........

[datzenmike]

With the key, on have someone depress the gas pedal. Listen near the solenoid there should be a clicking sound. No sound would likely mean it isn't working.

 

If power is good before the switch and slightly lower after, that sounds right. The solenoid has a coil of wire which will have some resistance.

 

Try providing a good ground on the wire coming out of the tranny. If the old ground is poor, this may fix it. If there is still no sound, replace the solenoid.

 

I think the 3N71B was used in 510s after April '71. They are a good reliable automatic.

[Datsun fan]

No clicking sound near g/b :( and there is good ground to the g/b :angry:

 

How to test that solenoid using multi-meter , how much OHM resistance should it be?

 

How to get new solenoid and replace it ?

 

THNX Mike , I appreciate your reply .

[datzenmike]

No clicking sound near g/b :( and there is good ground to the g/b :angry:

 

How to test that solenoid using multi-meter , how much OHM resistance should it be?

 

How to get new solenoid and replace it ?

 

THNX Mike , I appreciate your reply .

 

I would think you would hear a click sound if it was working. Could be wrong.

 

Use the ohm scale. Any rading means the wires insid aren't broken and the commection is complete.

 

Pull one off another 3N71B, there were lots made and I seriously doubt they made one for every car different. Find one in a wrecking yard or ask here. Looks like they just screw on like the oil pressure sender on the motor. Someone has one laying around. They are $100 at dealer.

[Datsun fan]

I tried to whack the diaphragm gently when key is on and kick down switch is on also and the solenoid worked sometimes (I heard weak clicks) , so either poor wiring or the

solenoid is going bad .I tried to feed the solenoid with good + .... no luck, tried with g/b housing as ground to black wire and HALLOOOYA It clicked well loud and strong!! I think the black wire coming out from g/b is bad or (half working) wire, I'll try to replace to be sure .

Again...... thnks Mike

[datzenmike]

Ah, the ground side. Power is important but it also had to have a good return (ground) circuit.

[Datsun fan]

I used a small test bulb on that ground I suspect,when cranking engine the bulb light came on and was pretty

dim, This confirm that the black wire coming out from g/b HAS NOT good ground . I gave it good ground and the

problem is gone ...... a damned tricky problem!