pcard

Hi guys, just to begin I have done a number of searches on the questions below. Either the answers are not there, or I am getting slow (both I think).


All for a 1970 Cutlass:


Question 1 and 2 are for emergency repair purposes:


1. What is the gauge and length of the fusible link wire? Are there any preferable makes?


2. Can the Ignition resistor wire (points setup) be replaced with a regular wire and resistor in series, and if so, what gauge wire and what value resistor?
I looked for this wire on Napa etc. but could not find it.


3. I am thinking of changing my starter circuit to include a relay to power the starter solenoid with a direct fed off of the horn relay/junction block. Can anyone advise of a good quality relay and what size fuse to use for the feed?


4. I am thinking of changing my power top circuit to include relays to avoid pushing the feed through the switch. Again, can anyone advise on a relay and size of fuse?

joe_padavano

Rule of thumb is that the fusible link wire should be one gauge smaller than the wire you are trying to protect. Length is irrelevant. All you need is a few inches of fusible link wire.

Yes, it's called a ballast resistor. Chrysler used this instead of a resistor wire.




This is an excellent idea and will pretty much solve any hot start problem. 30A should be sufficient. Just get a generic automotive four pin relay and socket.

Find out what amperage the circuit breaker is rated at. Again, one of the generic automotive relays should be fine. Actually, you'll need two, one for each direction.

pcard

Thanks Joe.


Re. question 2, there seems to be a few different resistances available. Which would best be suited for the 1970 455 standard coil?


Re. question 4, the factory circuit breaker for the power top was 40amps, but I think that the power windows would draw off of that also, and for that reason was not sure if a lower rated fuse to power the would suffice. Come to think of it, I can feed the relays from the factory circuit breaker and not worry about a fuse.

MDchanic

Peter,

2. Here's a chart of ballast resistor resistances from an old Glenn Manual. Looks like it's 1.35Ω:





4. They make the little black cube automotive relays in 30A or 40A. There is no external difference, and the prices are about the same.
Just get the 40A.

- Eric

pcard

In addition to using a relay for the starter, would it be acceptable to power the headlight lamp switch via the 87a terminal on the relay, so that if the light switch was in the "on" position the lights would turn off momentarily while the starter is engaged?

pcard

Thanks Eric.

MDchanic

Sure, but why? You can do that with your hand.

- Eric

oldcutlass

For the starter I like to use a Ford type solenoid, it's what they are made for.





The "I" terminal on them comes in handy when your using a mini starter that has no way to run a bypass wire to your distributor.

pcard

I guess that would be too simple

pcard

Hey Other Eric - I do not understand the wiring diagramme for the Ford relay.
Does this setup not have a direct heavy wire from the battery to the solenoid upper terminal? Is this where the starter gets its cranking power from?

oldcutlass

It does away with the purple wire to the starter. There would be a heavy wire going from the big lug on the solenoid (B Terminal) to the big lug on the starter. Then there is a smaller jumper from the big lug on the starter to the "S" terminal on the starter solenoid. It prevents the heat soak problem and you don't have a hot wire to the starter at all times, only at start.


It also creates another main power junction through the "A" post on the solenoid that you can tap off of to power an Hei through an aux 30 amp relay that can be triggered off the resistor wire.

joe_padavano

The Ford solenoid is a popular wiring change (note that I carefully did not use the word "upgrade") to the GM starter circuit. Unfortunately, it is usually done for all the wrong reasons. The reason why the Ford solenoid "fixes" the GM hot start problem is NOT because it switches the main battery cable. It is because it lets you put that little jumper from the main power cable to the S terminal on the GM starter. Note that this does NOT bypass the GM solenoid contacts - they are still required to carry full battery current for the starter to operate.

The real reason for the GM hot start problem is the resistance in the starter wiring, from the battery to the ignition switch to the NSS to the firewall connector to the solenoid. Adding a Ford relay and a jumper to the S terminal bypasses this resistance drop, but at the cost of adding two more potential corrosion prone connections and another set of high current solenoid contacts. Simply using a 40A relay to provide battery power directly to the S terminal and leaving the stock battery cable untouched (assuming it is in good condition) will do EXACTLY the same thing.

This has the added advantage that you don't need to install a Ford part in your Oldsmobile.

joe_padavano

Here's my suggested starter relay wiring.

pcard

Thanks Joe. Any suggestion on where to mount the relay?
I was thinking of putting it under the dash. I would run the supply lead through the accessory grommet. Then, break into the purple solenoid wire at the neutral safety switch connector, connect the 85 to the neutral safety switch connector, and the 87 to the purple wire that extends on to the starter solenoid. This would mean I would have to run an extra wire in plane view in the engine compartment.
Your circuit diagramme lends itself to mounting the relay closer to the starter, perhaps low down on the firewall, but I would be concerned about water getting in.
Thoughts?

MDchanic

Joe is exactly right here.

I've had the same problem (in my Chevelle), and used the same solution.
In my case, turning the key to START would seemingly do nothing (no clicking, no cranking), but the ammeter would swing to -30A, indicating that current was flowing through the solenoid, just like it always had.
I had the whole thing apart and together a couple of times, and had replaced the solenoid, before I finally figured out that the factory wiring was supplying enough current to deflect the ammeter, but not quite enough to actually pull in the solenoid.
When I jumped the solenoid straight to the battery cable, she turned right over.


Anywhere you'd like, but on the firewall is certainly the closest and easiest place.
You can find plenty of places to hide it, if you prefer, or you can use an original GM relay, like the one used for the power window circuits in many fullsize cars, so that it looks like it belongs there.

- Eric

joe_padavano

Your idea will work, but you want to keep the wiring between the starter and the relay as short as possible to minimize resistance. Personally I'd mount the relay on the engine side of the firewall, near the brake booster. I'm not particularly concerned about water on the relay at that location, but if you loose sleep over it, get one of these GM style relays with the environmentally sealed connector:

pcard

Joe - now those are sporty! Made in USA too.
Where can I get one of those? I googled to no avail.

joe_padavano

Google waterproof relay

pcard

Thanks Joe - could not find one made in USA, but have one from Hella in my shopping cart.