Again,2007 FX35 Infinity keeps blowing 40 amp fuse, pt#24370-C9900. No start takes place, obviously fuse controls ign,starter,alt systems. Most likely cause please?

What all does that fused supply B+ voltage too ? Do you know ? That would be your first thing to find out ! Do you know what a electrical distribution diagram is ? Do you know how to test electrical circuits with a DVOM - digital volt ohm meter ? Do you know what a short to ground is ?
Which fuse ? IGN A - 40 amp ,under hood fuse / relay box ? This fuse powers the Starter Relay and Ignition and Start Switch
Does your vehicle have a manual or automatic transmission ? The starter relay could be shorted inside , It's also located in the under hood fuse box . If you pull the relay out of the box it's plugged into an look on the bottom of it you would see four sets of numbers ! 30 & 87 an 85 & 86 . If you were to jump 30 to 87 in the relay box the starter should spin the engine over , not start an run just spin ! 85 & 86 is the control side . Could be the ignition switch !
That 40amp fuse powers a lot of subsystems !

Here is a web site for free diagrams !
http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model an engine , Under system click on electrical distribution , under sub system click on power distribution . Then click the search button .Click blue links one at a time . First blue link scroll down to the second diagram . You will see Ign A 40 amp fuse at the top of the page .you will also see it powers the igintion switch ,look at last part of ignition switch , when in start or run that 40 amp fuse powers all those other fuse's plus three relays i see there also . A/C compressor relay , rear window defroster relay ,daytime running lights . Any one of those circuits could have your short . You need to isolate the circuits , pull fuse's till the fuse doesn't blow !

There are two fuses for the fuel pump relay. One fuse is load side of relay, that fuse also sends voltage to load side of asd relay, the asd relay sends voltage to several systems, two of which are the fuel injectors and ignition coil. I'm not telling you to replace, anything, but, you need to do some testing.
The other fuse goes to control side of relay, smaller amp fuse. I don't know the amp rating of the fuse that keeps blowing.
See that fuse, it supplies voltage to load side of fuel pump relay and also to asd relay.

You replace any blown fuse[--- one time only---

Then you have to go to wiring diagrams of the
circuit in trouble & find a problem

Hi Jeff , in what fuse box is this 10 amp ign. fuse located ? I am looking at a power distribution diagram and i see a IGN 3 10amp fuse located in the I/P fuse box ! Is this the fuse that blows ? I see where you replaced the 10 amp with a 30amp . That is never a good idea , you don't want to make your problems worst . Melt wiring harness , could start a fire . Do you know how to do electrical trouble shooting ? How to use a wiring diagram , power distribuition diagram ? That fuse is hot in the run , powers the rear Heat / A/C , automatic level relay, ESC - electronic suspension control module , rear wheel steering control module , Plus someother thing's depending which vehicle , Y91 - ULT . Your Taho doesn't have all this options . http://www.bbbind.com/free_tsb.html find the thing's that fuse powers , disconnect them one at a time till the problem goes away .

The problem could be a shorted park netual safety switch . Do you know what a wiring diagram is ? It shows all the componets involved in a electrical circuit ! You IGN.1 fuse 40amp , GM calls it IGN A fuse 40 amp . It feeds the ignition switch and pin 30 at the starter enable relay .When you turn the key to the start position it sends B+ voltage to #8 crank fuse , located in the I/P fuse box ,from there it goes to the park netual safety switch , to pin 86 or 85 of the starter enable relay ! If you pull the relay out of the fuse box an look on the bottom you will see this four set's of numbers ,30,87 & 85 ,86 You can test at the fuse box where the relay plugs in . Here is a video on how to test . The guy presenting the video uses a horn circuit , but it works the same way . It happens a lot , the park netual safety switch shorting out . It may or may not be the problem . VEHICLE RELAYS Operation Diagnosis
Here is a web site for free wiring diagrams
http://www.bbbind.com/free_tsb.html Enter your vehicle info . then under system click on engine , then under subsystem click on starting . Then click on the search button an a link will pop up , click on it .You will see all the componets , connections , wiring colors etc... for the starter circuit for your vehicle .

Have an auto electrician look at it.

I had the same problem just last week. It turned out to be the idle regulator. Every time the IR got hot it would blow the fuse. You can drive the car without it attached but get it fixed asap. Got one for $40 from a spare parts place ($200 brand new) and my mechanic mate changed it for me (looked easy enough to do it yourself). Good luck.

is the only thing not working the cigarette lighter? the fuse that operates it is usually the accessories fuse, it normally operates the interior light as well, which fuse box have you checked,there is most likely one under the bonnet & there also may be one under the dash as well, it might well be that the cigarette lighter element is the problem,try another lighter....hope this helps....cheers

You need a bigger fuse

make sure of two things one is any wires touching at the starter to ground or melted and or is the starter drawing too much amperage causing the fuse to blow.starter may have a dead short in it.

car won't start after putting on new starter (1994 ford tempo)