[gtstephenson]

Background:
I just completed a Street Fire HEI install in my 71 El Camino. I did some homework prior to the install and recognize the requirement for increased current to the HEI unit over the stock ignition. I decided I should install a relay along with some really healthy wire (12 gauge) to be sure things would work properly. - I followed recommended procedure and tape off the yellow wire from the distributor and connected the red wire to the control pin on the relay.

Now for the problem.
Engine runs great. Starts easily and all. But the engine doesn't quit when I turn the ignition off. I measured 8V on the red wire connected to the relay. I have no idea why there is 8V on that pin. If I pull the wire from the relay the engine shuts off properly and there is no signal on the wire (without it being connected to the relay). At first I thought the relay was defective. Bought another relay but have the same results.

Anyone have a clue as to the source of the signal ?

Thanks for any ideas..

Tom Stephenson

 

[ccc]

put a resistor in the line and it will solve the issue.or you could put a small light bulb in the line and it will also do the same.

 

[xcookpac]

My understanding is that the Delco DN alternator was phased out within Chevrolet product lines at various dates during the late 1960s and early 1970s. Meaning that your 1971 EC may have a a Delco DN alternator (with external voltage regulator) or a Delco SI alternator (with internal voltage regulator). Last time I had alternator resistor issues was with an SI alternator (in that instance it was in a SI to CS 130 swap). I seem to remember the resistor needing to be a minimum of 50 ohms and maximum of 250 ohms for the resistor (radio Shack should stock such resistors). Can anyone else confirm the resistor ratings.

Usually (in SI alternator situations) this resistor is placed in the line of the excite wire on an SI alternator (two wire plug on SI alternator has two wires: i.) little wire also known as the excite wire or #1; and ii.) a bigger wire known as the sense wire (as in sense how much voltage exists).

.
This image is from an inline6 Jeep (pic that I had handy but most importantly it has clear picture of an SI alternator).

Assuming that you have an SI alternator, I would think that I would test the problem by seeing if the motor shuts off (when the key is off and it continues to run on)by removing the two wire plug from the SI alternator. If removing the plug from the alternator causes the engine to shut off, then I would place the resistor in the excite wire near the alternator (cut excite wire and splice in resistor with solder and shrink-tube). Alternatively, if removing the SI plug does not shut the engine off while in run-on mode (viz., key is off, but engine continues running) then try removing ignition switch connector from the ignition switch. If removing the ignition switch connector works then you are back feeding from somewhere else (very unlikely put possible if a lot of people have monkeyed with the harness).

I have attached a picture of the SI (internal voltage reg.) and DN (external voltage reg.) alternators. The alternator on the left is the SI (plug on top) and on the right is the DN alternator (plug in back).

If you have a DN alternator then the resistor is placed in the accessory wire for the ignition switch. See image below.

Let us know what you find out.

 

[gtstephenson]

I have a photo (how to insert here?) of the alternator connections. This looks like the SI unit but it has two wires in the same connector body (aside from the B+ wire) in the connector.

I can install a resistor but would like to know the wattage and resistance value required. And since there are two wires (blue and yellow), need to know which wire.

Thanks

Tom Stephenson

 

[gtstephenson]

Oh yes, the engine does shut off (ignition off but engine running) when I remove the connector with two wires (blue and yellow).

Tom Stephenson

 

[xcookpac]

How to Post Photos

I have a photo (how to insert here?) of the alternator connections. This looks like the SI unit but it has two wires in the same connector body (aside from the B+ wire) in the connector.

I can install a resistor but would like to know the wattage and resistance value required. And since there are two wires (blue and yellow), need to know which wire.

Thanks

Tom Stephenson

Tom:

I just bumped a thread from the other day on how to post photos that I posted. You should look closely at the screen shots that I posted. Be aware some people as noted in this thread can only copy by right clicking on the enlarged image while I can only copy from the photobucket picture by hovering over the fourth yellow little box and clicking. Like I said see my screen shots and it will make sense.

 

[gtstephenson]

OK, I've uploaded a photo to photobucket.

 

[xcookpac]

Tom:

You clearly have a Delco DN alternator (you can tell that because the R and F wires plug into the back of the alternator) same side of alternator as the output (AKA battery) terminal is located upon. Which means that the 50 to 250 ohm resistor wire should be placed into the accessory wire.

Make sure you test this analysis before you start cutting and installing a resistor. You should determine the color of the accessory wire at the back of the ignition switch then look for that same color on lug 4 of the voltage regulator (lug 4 should have two different wires - make sure you get the right wire). Try disconnecting the accessory wire from the voltage regulator while the run-on condition occurs. Disconnecting the accessory wire from the voltage regulator should cause the motor to stop running, Further you may be able to install the resistor in the accessory wire adjacent to the voltage regulator (this would likely be an easier install).

Let us know your progress.

 

[ssr71]

I can't see how the alternator has anything to do with this. If you installed a relay to act as a switch, then it should cut off 100% when the trigger voltage goes away. Did you use the original coil wire as the relay trigger?

 

[Beepster]

My understanding is that the Delco DN alternator was phased out within Chevrolet product lines at various dates during the late 1960s and early 1970s. Meaning that your 1971 EC may have a a Delco DN alternator (with external voltage regulator) or a Delco SI alternator (with internal voltage regulator). Last time I had alternator resistor issues was with an SI alternator (in that instance it was in a SI to CS 130 swap). I seem to remember the resistor needing to be a minimum of 50 ohms and maximum of 250 ohms for the resistor (radio Shack should stock such resistors). Can anyone else confirm the resistor ratings.

Usually (in SI alternator situations) this resistor is placed in the line of the excite wire on an SI alternator (two wire plug on SI alternator has two wires: i.) little wire also known as the excite wire or #1; and ii.) a bigger wire known as the sense wire (as in sense how much voltage exists).

http://i436.photobucket.com/albums/qq87/xcookpac/JEEP_SI.jpg.
This image is from an inline6 Jeep (pic that I had handy but most importantly it has clear picture of an SI alternator).

Assuming that you have an SI alternator, I would think that I would test the problem by seeing if the motor shuts off (when the key is off and it continues to run on)by removing the two wire plug from the SI alternator. If removing the plug from the alternator causes the engine to shut off, then I would place the resistor in the excite wire near the alternator (cut excite wire and splice in resistor with solder and shrink-tube). Alternatively, if removing the SI plug does not shut the engine off while in run-on mode (viz., key is off, but engine continues running) then try removing ignition switch connector from the ignition switch. If removing the ignition switch connector works then you are back feeding from somewhere else (very unlikely put possible if a lot of people have monkeyed with the harness).

I have attached a picture of the SI (internal voltage reg.) and DN (external voltage reg.) alternators. The alternator on the left is the SI (plug on top) and on the right is the DN alternator (plug in back).

http://i436.photobucket.com/albums/qq87/xcookpac/SI_DN_alt.jpg

If you have a DN alternator then the resistor is placed in the accessory wire for the ignition switch. See image below.
http://i436.photobucket.com/albums/qq87/xcookpac/GM_external_reg_alternator_wiring.jpg

Let us know what you find out.

Now, I'm not at all familiar with a DN alternator, but I am familiar with an SI 1 or 3 wire alternator. The colored photo (by itself) is a 3-wire. There are two wires in the plastic plug (mine are red and brown with red being much bigger). The red wire is connected to the terminal post (normally above, on the alty), along with the wire that runs to the battery to recharge it. The brown wire is the "excite" wire for the "idiot" lite or the volt meter. There is only one wire for a one wire alty, and that comes off the post. The charge to the battery is dependent upon rpm to "excite" the charge. Oh, and there's a mixture of the two (I have one). The connector recepticle for the 3-wire has a rubber cap on it. You don't have to use the plastic connector with the red and brown wires. Just connect the post to the battery, and it will act as a 1-wire. Personally, I prefer the 3-wire connections, and that's how I wired a 140A SI alty about a week ago.

 

[acauth1]

I can't see how the alternator has anything to do with this. If you installed a relay to act as a switch, then it should cut off 100% when the trigger voltage goes away. Did you use the original coil wire as the relay trigger?

x2 here. Where did you pick up voltage for the hot side of the relay coil?

 

[gtstephenson]

Ok, I have a working system now. The alternator *does* have an external regulator. I would have sworn it did not but you guys know best. I dug thru the alternator wiring and found that after going behind the headlight on the passenger side it worked it's way to the drivers side where hidden way behind the canister is a voltage regulator. I couldn't get to it without removing a bunch of things but I could see that on connector #4 was that blue wire from my alternator. So I then did install 200 ohms (two 1W 100 ohm resistors in series) over near the alternator where I could easily undo bundle the wiring.

Starts, runs and shuts down on command.

Thanks so much to the experts on this forum.

Tom Stephenson

 

[gtstephenson]

x2 here. Where did you pick up voltage for the hot side of the relay coil?

This HEI distributor has a coil built in. Only one wire to connect (the red wire from the ign switch). But it's pointed out that energy from the alternator feeds back thru the ALT lamp and the ign circuit keeping the relay held in.

The relay has no spec that I could find that would identify the drop in or drop out voltage but 8V from the alternator was sufficient to keep in engaged.

The resistance in that circuit is sufficient to lower the signal and allow the relay to disengage.

Thanks guys

Tom Stephenson

 

[acauth1]

Where did you pick up voltage for the hot side of the relay coil?

From the original coil + as relay coil + as ssr71 asked?

 

[xcookpac]

Tom:

Good work and thanks for letting us know the outcome. Sometimes it takes a little detective work to solve these wiring mysteries especially on a 40+ year old car. Make sure you either take pictures or write down some notes on the various wire colors and their respective posts so that you have some base to work from if new problems should develop.

 

[fauxrs]

what exactly is the purpose of the relay in the first place? is it part of some security system? I've done a dozen or more HEI conversions on points equipped cars and not a one of them required a relay to function so I'm a bit confused.

I have used relays with momentary contact switches to act as an ignition cutoff for security though so I'm just curious.

 

[Jack_K]

what exactly is the purpose of the relay in the first place? is it part of some security system? I've done a dozen or more HEI conversions on points equipped cars and not a one of them required a relay to function so I'm a bit confused.

I have used relays with momentary contact switches to act as an ignition cutoff for security though so I'm just curious.

I assume it's because the voltage to the original distributor is only about 8 volts under load, but the HEI needs 12 volts. He's using the "8 volt" circuit to energize the relay that will supply 12 volts to the HEI. At least that's the way I read it.

Jack

 

[fauxrs]

I assume it's because the voltage to the original distributor is only about 8 volts under load, but the HEI needs 12 volts. He's using the "8 volt" circuit to energize the relay that will supply 12 volts to the HEI. At least that's the way I read it.

Jack

OK yeah that would work, a bit more involved and requires a lot more wire.