HVAC blinks but no codes present - ZR-1 Net Registry Forums

Matt B · 10-24-2021

The headline says it all: I have a blinking HVAC LED short after starting the engine but there are no error codes present. A/C work well and I can't spot any other malfunctions.

Any ideas?

TX '90 ZR1 · 10-24-2021

Does the light blink over each button that is selected or just in the off position? Most common cause of blinking light, in my experience, is a code 9 low freon.
To start with I would disconnect the battery for a couple of minutes. Be sure and check the condition of the battery connections while you have them loose. A dirty battery connection can cause all sorts of issues with the electrical system.

GOLDCYLON · 10-25-2021

Correct 9 out of 10 times the blinking light is low Freon condition.

Matt B · 10-25-2021

The flashing comes over each button, so also in those conditions where A/C is off.

When is that code 9 triggered? Before it quits working or when it's "too late"? I'm asking because cooling works well.
Interestingly when she was imported all freon was removed with no pressure left in the system. Under that condition no "low freon" code was set in the system at all...

TX '90 ZR1 · 10-26-2021

Matt,
My experience with this is that the AC compressor will not engage when a code 9 is present. This makes your situation curious.
By disconnecting the battery the code will clear and allow the compressor to engage until it picks up the code again.
My suggestion would be to check electrical connections, check AC system pressures and verify correct cycling of compressor.
If blinking light persists after verifying above is correct get into the FSM and follow the troubleshooting steps.
Let us know what you find.

Matt B · 10-27-2021

Well... As said... Not much to troubleshoot...

Everything works as desired, from A/C operation to vent control. No codes set. I entered the HVAC diagnostic mode right after turning on the ignition, right after starting the engine, immediately after the LED started blinking. The error code layer of the menue constantly reports "00" - no codes present. This is really strange. Maybe an error with the HVAC control unit diagnostic mode itself?
When all refrigerant was removed the A/C compressor didn't engage as you said - BUT there was no Code 9. When I refilled the system it immediately started working after a certain refrigerant charge was reached. No battery disconnect needed.

I think I'll observe it for a while to see if it narrows down to a point. Really strange...

TX '90 ZR1 · 10-28-2021

Matt,
Seems really strange to me as well.
If the AC was activated with no pressure I would certainly think that a code should have popped up.
Maybe someone more knowledgeable than me will chime in with some thoughts.
Keep us posted to what happens.

Matt B · 10-28-2021

I certainly will

. However over here fall has become serious and winter is straight ahead. I don't think my ZR and I will have many dates in a foreseeable time. Usually we have grit salt on the roads from mid November until march or even April. Wish I was in Texas, too...

TX '90 ZR1 · 10-28-2021

Yep, here in Texas the weather allows us to ride our jackrabbits nearly year round!!
Texas Jackrabbit.jpg

Matt B · 10-29-2021

Hahaha, that's hilarious! I knew that things are just bigger in the states

10-24-2021	#1
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 523	HVAC blinks but no codes present The headline says it all: I have a blinking HVAC LED short after starting the engine but there are no error codes present. A/C work well and I can't spot any other malfunctions. Any ideas? __________________ ZR-1 #638/1991

10-24-2021	#2
TX '90 ZR1 Join Date: Oct 2017 Location: TX Posts: 2,027	Re: HVAC blinks but no codes present Does the light blink over each button that is selected or just in the off position? Most common cause of blinking light, in my experience, is a code 9 low freon. To start with I would disconnect the battery for a couple of minutes. Be sure and check the condition of the battery connections while you have them loose. A dirty battery connection can cause all sorts of issues with the electrical system. __________________ Kenny 1990 #442

10-25-2021	#3
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,155	Re: HVAC blinks but no codes present Correct 9 out of 10 times the blinking light is low Freon condition. __________________ 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

10-25-2021	#4
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 523	Re: HVAC blinks but no codes present The flashing comes over each button, so also in those conditions where A/C is off. When is that code 9 triggered? Before it quits working or when it's "too late"? I'm asking because cooling works well. Interestingly when she was imported all freon was removed with no pressure left in the system. Under that condition no "low freon" code was set in the system at all... __________________ ZR-1 #638/1991

10-26-2021	#5
TX '90 ZR1 Join Date: Oct 2017 Location: TX Posts: 2,027	Re: HVAC blinks but no codes present Matt, My experience with this is that the AC compressor will not engage when a code 9 is present. This makes your situation curious. By disconnecting the battery the code will clear and allow the compressor to engage until it picks up the code again. My suggestion would be to check electrical connections, check AC system pressures and verify correct cycling of compressor. If blinking light persists after verifying above is correct get into the FSM and follow the troubleshooting steps. Let us know what you find. __________________ Kenny 1990 #442

10-27-2021	#6
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 523	Re: HVAC blinks but no codes present Well... As said... Not much to troubleshoot... Everything works as desired, from A/C operation to vent control. No codes set. I entered the HVAC diagnostic mode right after turning on the ignition, right after starting the engine, immediately after the LED started blinking. The error code layer of the menue constantly reports "00" - no codes present. This is really strange. Maybe an error with the HVAC control unit diagnostic mode itself? When all refrigerant was removed the A/C compressor didn't engage as you said - BUT there was no Code 9. When I refilled the system it immediately started working after a certain refrigerant charge was reached. No battery disconnect needed. I think I'll observe it for a while to see if it narrows down to a point. Really strange... __________________ ZR-1 #638/1991

10-28-2021	#7
TX '90 ZR1 Join Date: Oct 2017 Location: TX Posts: 2,027	Re: HVAC blinks but no codes present Matt, Seems really strange to me as well. If the AC was activated with no pressure I would certainly think that a code should have popped up. Maybe someone more knowledgeable than me will chime in with some thoughts. Keep us posted to what happens. __________________ Kenny 1990 #442

10-29-2021	#10
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 523	Re: HVAC blinks but no codes present Hahaha, that's hilarious! I knew that things are just bigger in the states __________________ ZR-1 #638/1991