Starter relay or no starter relay, Been reading up for an hour and still don't know!! Options

[David Stowers]

On two occasions recently on pulling onto my driveway after a long journey my car won't restart after turning off to unlock the garage door. Luckily I can then just push the car in but with a European tour booked in the summer I'd like to sort the problem.
When I get back in after opening the garage the lights on the dash dim when I turn the key to start but there is no click. 20 minutes later it will start right up. Is this the problem that will be solved by a hot start relay kit or just a good old fashioned sticky solenoid? I'd rather do just the relay or just replace the solenoid so which is it?
Thanks guys

[stugray]

Tom,

That is a pretty good explanation. The technical explanation is that the current through an inductor (starter solenoid) cannot change instantaneously.
So when the switch is closed and ~35 Amps is flowing, then you open the switch (resistance goes to infinity), the current cannot stop flowing, so the voltage climbs to infinity to try to maintain the current flow until it reaches the breakdown voltage of the air gap (10,000 volts or better) before it arcs across.
This is exactly how the points & coil make the spark jump the plug gap and the gap inside the rotor.

The diode inside the relay in the picture above gives the current someplace to go so the voltage doesnt try to climb to keep the current flowing until it dissipates.

Solid state relays is the way to go.

A SSR would work, but it has to be the kind that can allow "avalanche breakdown" to dissipate the Reverse EMF or it will fail quickly. (that just means it keeps flowing current even after told to turn off).
The electronic ignition a lot of us use to replace the points is technically a SSR.