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

rgfllamas · 04-26-2009

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

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

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

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

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

Quote:

Originally Posted by rgfllamas

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.

Glad to have helped. Welcome to the forum. GC

04-26-2009	#1
rgfllamas Join Date: Aug 2008 Location: Palm City, Fl Posts: 32	flashing "sys", blowing fuse 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? __________________ Ken 63 vert 91 ZR-1 #786 91 Z-07 (sold) 67 coupe (sold) 72 LS5 coupe (sold)

04-26-2009	#2
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,120	Re: flashing "sys", blowing fuse 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. __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

04-26-2009	#3
HIZNHRZ Join Date: Apr 2004 Location: Germantown, MD Posts: 732	Re: flashing "sys", blowing fuse 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!

04-26-2009	#4
gbrtng Join Date: Feb 2006 Location: San Antonio area Posts: 1,177	Re: flashing "sys", blowing fuse 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). __________________ “Buy the best example of what you want, and pay whatever it takes. That way, you cry only once.” ~ Bruce Meyer Last edited by gbrtng; 04-26-2009 at 04:40 PM.

04-26-2009	#5
rgfllamas Join Date: Aug 2008 Location: Palm City, Fl Posts: 32	Re: flashing "sys", blowing fuse 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. __________________ Ken 63 vert 91 ZR-1 #786 91 Z-07 (sold) 67 coupe (sold) 72 LS5 coupe (sold)