Hi! Iam wrs my 1991 C4 when hot will not start,does not turn over,does not dim lights,no clicking,just nothing.I let it sit cool down and I here a clicking sounds like a relay but still does not crank.Then all of a sudden I turn the key and she cranks up runs find,dead cold always cranks and runs find drive to show shut it down hit the key she fires up ,shut her down hit key nothing!! But wait about an hour hit key fires up.I was thinking about the starter relay,or the safty relay.                ANY INPUT WOULD BE WELCOME

sounds like starter solenoid. probably need to replace starter. i've had the same problem on other cars before and almost always turns out to be the starter.

I'd agree with the starter solenoid. The solenoid can stick when hot. Usually, just replacing the solenoid will correct the problem, but....replacing the starter at the same time is a good idea...unless you just like taking the starter on/off.
One thing you can check before condemning anything, is voltage at the Purple(usually) wire on the solenoid. This will be the small wire closest to the engine on the solenoid. You really wanna check voltage here, not just whether or not it will light up a test light. You want a full 12v+ there with the key turned to "Start". If you see 12v at that terminal when trying to start, the ignition switch is fine, and the problem is most likely the solenoid. If you do NOT see 12v there with the key on "Start", then you prolly have a wiring issue, or an ignition switch that is failing.
hth

Agree wIth the solenoid is probably bad. Replace the whole starter while you are down there. I would also recommend adding a solenoid heat shield as well. They are a couple of bucks at AZ, Advance or Pep Boys. The shield bolts right on. The heat generated from the exhaust pipes is what kills your solenoid. Good luck!

Well there is nothing wrong with my starter, my clicking is coming from th dash or fire wall, but before I got to check this my alternator burnt up killed the batt well got new alternator coming don't know wheather to get 140amp or 105amp chrome or what ever and paint it o-well check the batt charge it up shows 12.5 volts that's good I hope this was my poblem along with 144,000 on her rebuilt eng.,trans,rear,suspension, ETC. all I can say is NEXT THANK YOU ALL FOR YOU INPUT WRS     (will let you know what happens)

The clicking is most likely the starter relay, but it could be any of the other relays, too, depending on which ones go on or off when the key is turned to "Crank". Try swapping the starter relay with another identical relay, and see if that allows the car to start. The relay may be just getting too hot, or the contacts may be pitted enough to make contact sometimes, but not every time....

Having had the same exact problem with my 1990 recently, and having to take it to the stealer to finally get it diagnosed, it did indeed turn out to be the solenoid. But it also turned out to be the cracked, baked, and cooked 20 year old wiring around the starter. I replaced the starter and the solenoid, and all the wiring as well as having them all heat wrapped to protect them.  Now if this will just last another 20 years I will be in GREAT Shape......LOL.

could the clicking sound be the fuel pump relay? should only hear it for about 2 seconds when you turn key on. also, i agree with the solenoid but is it also possible something is amiss with the vats system?

From past experience, I'd put the VATS and the fuel pump at the bottom of the "suspect list". The fuel pump clicking should only come from the rear (gas tank) and the VATS should not make a peep. Based on the description, there's a chance it's the relay to either of these 2 systems, but I'd put the actual systems themselves as a low possibility. Solenoid and/or relays sound the most suspect

105 amp or 140 depends on extras on the car i guess.