Need help with Starter fuse blowing

[95cutlass!]

I'm hoping someone else has experienced and solved this.  I have a 1995 Cutlass Supreme Converitble with the 3.4.  I bought the car 1 1/2 years ago with 44,000 miles and it now has 50,000 miles on it.  The car is stock and has no visible signs of tampering, electrical or otherwise.  It's in nice shape and was a California car...no rust anywhere.

 

For a while I was experiencing starting issues that seemed like a weak battery...engine was very slow and labored to turn over, just like a weak/dead battery, but the battery was new and tested fine.  Shortly before I replaced the starter, the car began occasionally blowing the starter fuse (5 amp located in the dash fuse panel) when starting the car with a warm engine.  I eventually replaced the starter with an old-stock GM rebuilt unit I purchased off of ebay.  The new starter seems perfect and solved the slow turn-over condition.  I also thought it would solve the occasional blown fuse too, but it hasn't.  In fact, the fuse is blowing more and more often.  It rarely (if ever) blows the fuse when the car is cold, but often does it if warm.  When it blew in the past, it would often blow before the starter energized.   I experimented with putting the car in neutral to see if perhaps the transmission range switch was the culprit.  That seemed to make some difference, but the fuse is still blowing.  Now, the starter will engage and start the car, but the fuse will blow during the starting process...starter stays engaged and starts the car.  

 

I removed the transmission range switch, took it apart, cleaned the inside and but it back together.  There was minor corrosion on the inside of it so I figured that it was the problem.  After reinstalling it, it does the same thing.  I guess it could still be a faulty range switch, but before I replace it I wanted to see if anyone else has ever experienced this problem.  I have the GM shop manuals, and the only other thing in this circuit  is a theft deterrent relay and a theft deterrent module.  

 

I appreciate any help or guidance.

[Imp558]

Looks like you were on the right track, it has to be a short to ground before the ground pin (A1) on the start enable relay. It could even be the relay itself.

 

 

I would unplug the relay and then pull the fuse and read across the terminals in the fuse block with a voltmeter or a light bulb to see if there's a ground. Cycling the P/N switch while I watch it.

Edited November 21, 2017 by Imp558

[95cutlass!]

Thanks for the input...that's great advice in finding the short.  To be clear on which relay, from the schematic, do you mean the one marked theft deterrent relay or the one marked theft deterrent module?

[Imp558]

Relay, I'm assuming it's in the UEC. If you straighten the pins on a 194 bulb it might sort of stay half assed plugged into the fuse socket. The relay can be tested with an ohm meter across it's coil after removal, then test a similar relay and see if your start relay may have a shorted coil with a significantly lower resistance causing it to draw more current.

[55trucker]

Reading the schematic I see the starter circuit not having an issue there's only the main 40 amp fuse that powers the starter side,

 

what DOES have an issue is the 5amp powered circuit that goes thru the transmission switch that feeds the VATS relay & the VATS module. The VATS circuit is paralleled off the ground side of the ignition switch. That circuit fails, the 5 amp fuse blows & the control side of the VATS relay won't energize to close the relay & the starter circuit doesn't engage.

 

A light tester would be simpler to use than a voltmeter, as suggested pull the VATS relay & also disconnect the VATS module, with the ignition on (start) & the trans in either park or neutral test the circuit at the fuse, then test at the input side of the trans switch, then on the output side. If you don't see a visible short move on to the input side of the VATS relay & test again (electrical center), if the harness between the relay and back to the switch is good move on to the ground side of the VATS relay, bypass the relay by bridging the contacts for the control side of the relay and check the control side wiring terminals. If at the relay you find there's no visible lack of test light ( the fuse hasn't blown) then now you're testing the circuit between the relay & the VATS module looking for the short.

 

With the relay pulled the starter circuit will not engage, testing the circuit before the relay you don't need the relay in place, the light tester acts as the load to complete the circuit. To test the circuit between the relay & the module & prevent the starter from engaging you'll have to bridge the contacts in the electrical center for the control side to keep the circuit live, when you find the damaged portion of the circuit you'll know quickly as it WILL get hot & blow the fuse. You need someone on the ignition switch to go to *start* to do this test.

[95cutlass!]

I really appreciate all of the input.  The relay checked out fine, and after more diagnosis, I decided to replace the Transmission Range position switch.  I found one at Pull-a-part out of a '95 regal.  After installing it, I drove the car for a while until it warmed up, and after that, the car started every time for probably a dozen tries and did not blow the fuse.  In the past It would have blown before that.  I need more time to be sure, but it seems this might have fixed it.  The car goes into winter storage tomorrow,

so I may not know for sure until spring.  The Cutlass & I thank you!

[Imp558]

There was precious little in that circuit to be grounded / shorted and the switch was the most complicated thing. It's probably safe to assume you got it.

[95cutlass!]

Welp.....I didn't get it.  I was at my dad's today and pulled the car out of the winter storage barn to drive it for a bit...it's still blowing fuses like crazy.  Granted, I replaced the transmission range switch the day before going into storage back in November, but I started it over and over back then and didn't blow one fuse.  I'll start over with the diagnosis in the spring.  In the mean time, shout out if you've ever experienced this problem.

[Schurkey]

According to the posted schematic, that 5-amp fuse is also powering something in the Air Bag system.  A ground or high-amperage draw in that will also pop that fuse.

 

The range switch is intended to ground via the VATS crap.  "I" would have a look at the VATS module.

 

Of course, grounded wiring anywhere beyond the 5-amp fuse would pop the fuse.  It could easily be a "harness" problem rather than a "component" problem.

[Imp558]

It's not VATS, that's on the wrong side of the load, just looking at the print again it looks like one could simply bypass the whole circuit by jumping the yellow and purple wires together. It would allow the starter to engage with the shifter somewhere other than park or neutral.

I don't know what the airbag system would ever want a start signal for.

That could be a short term option to make it drivable until there's time to fix it correctly. 

[Grandprix1]

I wonder if the airbag gets its charge indicator from the starter. Just a thought though.

[95cutlass!]

FOUND IT!   FOUND IT!   FOUND IT!!!!  Hallelujah I found it!!!   This thing has taken me FOREVER to figure out, partly because it was intermittent, and partly because the wiring diagram was a little confusing.   At first glance at the diagram from the GM shop manual (same as above) it seems like circuit 806 is only a purple wire.....I couldn't find a short in the purple wire ANYWHERE and all of the components connected to it checked out fine as well.  After working on it for a long time last night the problem went from intermittent to continuous blowing of the fuse, which helped in the long run.  I decided to check the yellow wire running from the transmission range switch back to the starter relay even though it at first appears not to be in circuit 806 (they just didn't label it there).   The yellow wire was shorting...the location turned out to be on the right side strut tower where the harness runs near the power steering line...the hard line was bent slightly out of place and rubbing the harness....I will sleep well tonight!     

 

Thanks to all who offered input.

[vipmiller803]

Thank you for reporting the update. Congratulations on finding the short! wiring harness shorts are the worst...

[ron350]

Glad you found the problem.

 

Can you post a picture of  the spot where the wire shorted?

[95cutlass!]

Glad you found the problem.

 

Can you post a picture of  the spot where the wire shorted?

I hope to post a pic tomorrow.