flashing "sys", blowing fuse [Archive] - ZR-1 Net Registry Forums

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rgfllamas

04-26-2009, 02:49 PM

About a week ago I jumped in the car, a 91, and tried to start it, no go. Battery was low, it had been sitting 2 or 3 weeks. I pulled out the trickle charger and let it charge overnight at about 2 amps. Went for a ride yesterday, and noticed the "sys" light flashing and I was unable to get any readings from the DIC. Sys alternated with the instant MPG display which always displayed "0". I couldn't switch to any of the other options. Also noticed that none of the lights were on on the A/C panel nor was anything displayed on its read out.

Got home from the ride and grabbed the FSM to try to figure out what's going on. Tried to pull the codes but was unable, checked the A/C fuse since the manual says if it's blown you won't be able to pull the codes. It's gone. Installed new fuse and tried again. It blows. Checked the archives and saw a posting about side terminal batteries that also have top terminals shorting to the frame. I checked and sure enough it appeared to be shorted. I insulated the top post, replaced the fuse and tried again. It blows.

The electrical supplement shows that 10 amp A/C fuse supplying about 9 or 10 different circuits. As far as I can see the only way to find the short is trial and error, and if that's the case I need a whole lot more fuses.
I'm puzzled because everything worked prior to the low battery. I didn't boost or jump start the car, just used a 2 amp trickle charger, so I hopefully didn't overload anything, yet now I have a short.

Any suggestions before I go looking for a needle in a haystack?

GOLDCYLON

04-26-2009, 03:49 PM

Unhook the battery for about 30 seconds and hook it back up. The low battery may have temporarly hosed up the ECM. These C4s require and demand 100% battery power ALL the time. Flashing sys is normally a shorting battery/ undervoltage issue or is indicitive of a recent aftermarket radio install. However before replacing the battery I suggest unhooking it first and seeing if that clears it up.

HIZNHRZ

04-26-2009, 04:29 PM

While there could be other root causes, in all likelihood there is no need to go looking for a needle in a haystack. I've had the same problem (flashing sys), for the same reason (dead battery that needed to be charged) on several occassions. As GOLDCYLON stated, unhook the battery and hook things back up. You should not see the sys flash after hooking back up. Then - go enjoy the great weather!

gbrtng

04-26-2009, 04:31 PM

This sounds like what I saw with my wife's 91 L98 car last summer. As near as I could figure, there is a diode across the AC clutch coil that absorbs a current transient when the AC clutch engages and disengages, and it failed. Blew the 10 amp fuse every time the AC compressor cycled.

So, disconnect or disable the AC compressor and see if the fuse holds. I solved the problem by installing a slow-blow 8 amp inline fuse at the fuse box. Problem solved.

The point being, you need to disable as many of those branch circuits on that fuse that you can.
I ended up buying a DC clip-on ammeter so I could watch current flow in the circuit. The AC clutch draws about 3.5 amperes steady state, and the CCM probably less than one amp (I never managed to measure that one).

rgfllamas

04-26-2009, 04:54 PM

You are the BEST!!

I disconnected the battery and went to Wallie World to pick up some fuses after making the first post. Just got home and read your responses. Went out to the garage, hooked the battery back up, replaced the blown fuse and fired her up. No "sys" and the DIC is now working. A/C system came right up, just like it should.

So much better than trying to track down a short that doesn't exist. That kind of stuff is sooo frustrating.

I'm back in business.

Thanks all.

GOLDCYLON

04-26-2009, 11:12 PM