Can somebody please help me identify what may be some kind of relay on my 72. It is located in the engine compartment, under and to the left of the coil. It has a plug-in to the wiring harness that may or may not be part of the signal/hazard light harness. Thanks!

Bill

Sounds like your car is an automatic to me. Or was originally. If so, that relay has something to do with the shifting from one set of points to the other in the automatic's dual-point ignition.

Bill, If you are using the original dual point distributor and an automatic transmission as Arne mentioned, let me know and I can dig up the specifics for you. If not..no point.:classic:

Yes, it is an automatic. I was concerned about it working because the previous owner(s) painted the engine well with no regard to covering these types of things. The connector is also covered, and the connections inside are in need of cleaning. How can I tell if it is working properly? Thanks again!

Bill

1 Any malfunction of the spark timing control system (cars with automatic transmission) will probably be due to a failure of the water temperature switch or relay.

2 The water temperature switch can be checked as described in Chapter 3, Section 23(.

3 The relay can only be checked by substitution, unless is is removed for testing by a competent auto technician.

Chapter 3, Section 23(

( water temperature switch

10 Testing the operation of this switch can only be carried out if an ohmmeter and thermometer are available. Connect the switch plug to the meter and then immerse the switch in water which is at a temperature of 77 deg. F. The onmmeter reading should be infinity (switch open).

11 Heat the water until between a temperature range of 88 and 106 deg. Fthe ohmmeter reading falls to zero (switch closed).

The water temperature switch is referred to as THERMO-SWITCH in Ron's attachment. I guess that doesn't help you much, really. Aren't we "competent auto technicians"? There has to be a test somewhere for that relay. Perhaps in the FSM?

I agree Stephen. Although I've never seen this particular relay in person, from what is shown in the drawing, there is nothing complicated about it, but I would heed the warning and test it while it is disconnected from the distributor. This is from late 1970 and is the only thing I've seen that explains the system.

This is from the 'Datsun Engine Analysis-Performance and Emissions 1970-1980' manual. Not really a test of the realy but a test of the system.

Yes, it is an automatic. I was concerned about it working because the previous owner(s) painted the engine well with no regard to covering these types of things. The connector is also covered, and the connections inside are in need of cleaning. How can I tell if it is working properly? Thanks again!

Bill

Bill you didn't say weather or not you are still using the old duel point Dist. or not. If you have changed to a ZX or other up grade ignition , then the relay is out of the loop. I left my relay there only because it gave me a place to connect the unused OEM plug. Gary

One other thing needs to be pointed out here Bill. The information Stephen provided is more accurate for your car, as it is 1972 specific. The information I provided is from 1970 and references the earlier 3N71A transmission. I believe the methods of operation are identical with the only difference I noticed was the air temperature switch sense of 40 degrees which is measuring ambient air temperature in the 1970 example and the water temperature switch that Stephen noted for 1972, that measures water temperature (a definite improvement). I have seen the factory manuals that cover the newer 3N71B transmission up for auction on Ebay occasionally, which will most likely cover this in better detail.

Bill, you will have to confirm this for us. In Post #7, in the attachment Stephen provided titled Spark Timing Control System for Automatic Transmissions 1972, the ambient temperature of the passenger cabin is being used to trigger the Temperature Switch at 50 degrees and not a water temperature switch. I think because the Haynes manual referenced in Post #5 covers many model years that point was skewed and sent me down the wrong path. That's what happens when you don't have the car in front of you. Just a point of clarification.