Barry A. Waters

Folks,

I've recently started to experience an intermittent electrical fault that I'm chasing and hope someone can help. Did a search on past posts with no luck so here we go. I have the Helms factory manual set (about five books total) so that's what I'm using to diagnose. Here's what I know so far...

While driving along normally with AC on (and cooling well) and no Warning Lights lit on the Instrument Panel Cluster, the following infrequently occurs all at once:

AC Blower shuts off
AC Compressor shuts off
AC Control Head loses power
ABS Warning Light in IP cluster lights
Brake Warning Light in IP cluster lights

Engine continues to run fine and truck is very drivable with only the exceptions noted above. When this happens I shut AC and Blower off as a precautionary measure. In a few minutes (or after a shutdown/restart) the IP ABS and Brake Warning lights go out, the AC Compressor & Blower come back on line and everything functions as it should.

A check of the ABS Control Module shows a single code set, 65. This alludes to a 'Power or Ground' fault with the ABS Pump Motor. That seems to account for both the ABS AND Brake Warning IP lights as the latter can be set by the ABS failure.

The schematics show that ALL of the systems above receive their Ground connection from Ground 105 (G105 - Engine Ground) after passing through Splice 107 (S107). And here is where the schematics fail me for the 5.7L engine.

There are conflicting diagrams/text as to where G105 is located. On the left side of the engine block? On the right side? On the right fender-well next to the battery? G101, G102, G103, G104 and G105 show up in various locations in the 5.7L diagrams and G105 appears and disappears depending on where you look. Maybe I should have subscribed to the 'correction bulletin' service?

Anyway, my next step is to find every Gnnn Ground Connection I can discover and clean them all - can't hurt! Hoping that will serve...

Does anyone know where G105 is located on a 1995 5.7L? Or Splice S107 for that matter? Sure does look like a Ground failure as no wires or fuses in the circuits (CKT 150 for Ground on everything above and CKT 442 for Power to the ABS Module) appear to be smoked. Remember, things come back on line after a bit.

An automatically resetting Circuit Breaker (Thermal?) could exhibit this behavior but I'm not finding any in the schematics other than the two in the IP Fuse Block (on the left side of the dash) that serve the Power Locks/Seats and Power Windows.

At a bit of a loss here and hope that cleaning every Ground in sight will resolve this but still have to wonder if someone has been down this road (circuit?) before and could back me up or lead me down the right path...

Barry

Barry A. Waters

Folks,

Lots of good work/finds and still no certainty on locating Ground G105 for my truck BUT the 'drop out' problem has not occurred again so I don't really know if I've fixed it or not. I don't believe I have but we'll see. What I DO know is that I've certainly done a world of good for the rig's overall 'Ground Health', something that was probably LONG overdue.

I've been testing using the HVAC Blower as a litmus as I find and disconnect each Ground (one by one) and it has continued to work well with each disconnected. When I truly find (and disconnect) G105 the blower should go INOP or, at least, work poorly via a 'sneak ground'. Next time my 'drop out' happens I need to turn the Windshield Wipers on to see if they are INOP as well - one more pointer to G105 if they are.

It's amazing how many grounds in the engine compartment are not accurately identified (or even listed) in the factory manual's electrical schematics...

I've attached an interesting .PDF w/photos of my recent 'Ground Search for G105' and hope it may help someone (me?) I think I MAY have closed in on G105 and possibly found it - see the .PDF for details. It's a connection that's pretty difficult to get to so I haven't been able to disconnect/test/clean it yet. Hell, I can't even get a look at it - only 'feel' it.

Anyway, give the .PDF a look and DO let me know if you know of any Ground Connection Locations (Gnnn type) for a 1995 C1500 w/5.7L Engine to add to the document.

I'm also VERY interested in exactly where Ground G200 (Instrument Panel Ground) is located. The manual says "Behind LH Side of I/P, Below Fuse Block" but does not have a figure (image) reference. I see nothing obvious on a quick inspection but haven't removed any trim panels yet. Does anyone have a photo or a better pointer to G200's location?

Barry

TexasChevy31

Had huge ground problems like blinker setting off unstoppable windshield wipers and running light switch taking out headlights . Wiggled ground coming off back of motor to frame. Don't know how but fixed all eletrical problems.

Barry A. Waters

Was the Ground you 'wiggled' the one I show as potentially being G105 in Photo #8 of my .PDF file above? The Windshield Wipers on the schematics I have for a 1995 C1500 5.7L indeed show G105 (via Splice S107) as their primary Ground. Not seeing the other circuits you mentioned grounding through G105 (lights/turn signal) but with 'sneak grounds' strange things can happen. Glad you seem to have solved you issue!


Barry