Bypassing C500... (Page 1/1)
CSM842M4 JUN 30, 09:24 PM
I've got a thread going about our '84 2.5 that we were able to get started a few days ago, then (as now) it won't start. That thread is, I think, about to reach its logical conclusion, but while researching that problem, I came across another suggestion that might help prevent letting a known problem become a problem...
So, the two circuits or groups of circuits protected by fusible links coming from the starter solenoid - I've read recommendations to take those out of the C500 connector on the firewall and bring them in the car by another means. The justification for this is that either the terminals in the C500 or the connector housing cannot tolerate everything that COULD go through those circuits at once (worst case scenario, but ain't that what you want to prepare to try and prevent?). I'm thinking a pair of insulated bulkhead pass-through studs to get those circuits out of the connector but in the car where they belong. Not trying to re-invent anything, just trying to avoid trouble using a little foresight. Thoughts, anyone?
jelly2m8 JUL 01, 01:44 AM
HUH? your isolated pass through connection is the C500 connector. That's a pretty robust over built connector. that most likely isn't your problem.

Find your problem and fix that before you add a possible failure point.

The only output to the engine running in the C500 is the Starter Solenoid feed and Coil power, the rest are all mainly inputs back into the car, some gauges, fans etc.

[This message has been edited by jelly2m8 (edited 07-01-2024).]

theogre JUL 01, 08:50 AM

quote
Originally posted by jelly2m8:
HUH? your isolated pass through connection is the C500 connector. That's a pretty robust over built connector. that most likely isn't your problem.

Find your problem and fix that before you add a possible failure point.

The only output to the engine running in the C500 is the Starter Solenoid feed and Coil power, the rest are all mainly inputs back into the car, some gauges, fans etc.

Wrong. Read the Top Post Again. Note: '84 2.5

84 C500 has F-Link A to C500 E4 then to the rest of the car & This Pin is Easy to Over Loaded for Several Reason & Why GM eliminated this pin & move to another plan.
See https://web.archive.org/web...erocave/altsense.htm

Simplest way to bypass C500 is cut off E4 & splice them near by.
Or follow the rest of that cave page.

GM also stopped having Fusible Links connected to the Starter Solenoid in 85 MY because so many problems because of road crap etc attacking them. Even stopped CSI for V6 for this & more reasons.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

jelly2m8 JUL 01, 10:39 AM
Correct you are, missed the part it was an 84.
CSM842M4 JUL 01, 11:07 AM
I'm not saying this is causing my problem right at the moment. After some elimination, my current focus is the ignition switch. But I recall reading from one heavy hitter on this forum, while researching the fusible link portion of the current no-start, that the terminals (I think) in C500 were not up to the task of handling everything that could go through at least one of those connections at once. The wiring diagram he provided seemed to back up that assessment, with numerous circuits further downstream being fed by the circuits protected by fusible links A and B, and not only circuits related to the engine starting and running. Since this car is not yet in the daily-driver rotation, I'm not forced by a lack of time to put it back in service using tape and chewing gum; I have the luxury of being able to fix known issues before they become a problem for me. If the A5 and E4 question does indeed turn up as a common issue, I can head it off at the pass
CSM842M4 JUL 01, 11:12 AM
Thanks, ogre and jelly.
theogre JUL 01, 01:19 PM
A5 is Headlights & other light wiring. Believe both have bigger pins then all others to handle more power but E4 w/ the big pin is easy to over load for several reasons.

A5 could be cut out & splice like alt wires.
But...
May Still need HL Relays in Cave HL page because "Silver Star" class legal halogen bulbs max out power used but OE HL switches etc barely handle that power when new then any wear = higher contact resistance = more problems @ those points.

So eliminate A5 can be near worse-less because have relays w/ own link/fuse/breaker removing it's main load.

If have lighting problems...
Check first:
the HL bulbs as maybe old or others have used hotter HL that "eats" old switches etc.
all ground especially G101 G102 near HL's
See cave light pages for more common problems...

Note: While most "books" list only H6054 for Decades, many model lines more so w/ lower Trim Levels, not necessarily a "base models," actually had 6052 Standard Tungsten HL that are less bright to start & after years to decades of use even dimmer. Even I miss that in the cave HL page.
(Any w/ Round or 4 Bulbs Sealed Beam HL had same "problem.")
IOW 80's Cadillac Lincoln etc may have factory install Halogen SB HL but Others often did not or base models did not but "GT" & related trim might have the better lights.
CSM842M4 JUL 02, 07:35 PM
What I'm gathering from this is to get the E4 circuit through the firewall some other (safe) way than in the C500 connector, and hold off with going that route with the A5 circuit until/unless a problem shows up, yes? I was gearing up to turn a pass-through connector or two on one of my lathes at work, until I priced them; less than $8 a pop is is WAY quicker than sneaking in 20 seconds at a time, a couple of times a day, for a week and a half, even as much as I enjoy making my own solutions...
theogre JUL 03, 01:07 AM
Yea, leave A5 alone.

the pin will easily handle the lights.
If you use legal "Silver Star" that pulls more amps, the relays are best way to prevent the switches to die.

E4 does not need a pass thru connector.
Just crimp a closed eye on each end w/ a good crimper & use silicone or permatex green label break grease & a bolt to connect them.

Can use heat shrink crimp that has "glue" to keep out most crap. Use 3M not cheap crap from Amacon etc. 3M/Scotch cost more but most people not using many of them. Or Use "rubber" self seal tape not electrical tape.

You only need the eyes & bolt so that if needed can disconnect/reconnect later w/o making new joint.

GM did same thing just studs in plastic shown in https://web.archive.org/web...ocave/ecmwire_fl.htm