HVAC keeps blowing fuse - ZR-1 Net Registry Forums

biggiefl · 11-02-2018

I took my 90 to work one day and a/c worked fine. Parked and unplugged my radar detector. Came out of work and no air, no lights, nuttin. So I replaced the 25a fuse and it blew again. What do I need to check? Aux fan not kicking in? Not sure why it would work fine and then nothing so I doubt freon. I do have the FSM but not sure if I have the part for codes.

biggiefl · 11-05-2018

Wow! Everyone at corvetteforum.com always says to ask here for technical help. Guess not.

-=Jeff=- · 11-05-2018

sounds like a feed wire that go chafed.. Do you have the FSM? best place to start.

my best guess on the no reply is this is an odd issue and possibly not common so nobody has come a across it

9T1 Red ZR1 · 11-06-2018

Hello,
Page 1C1-16 of the FSM shows a diagram. You could try pulling the wire off of one of the two pressure switches to "break" the circuit and narrow down where the short may be.

Good luck,
Bill

biggiefl · 11-07-2018

Thanks for the replies. I got the same answer about a possible wire being chaffed. Will work on it as that makes sense on why it inconsistent.

GOLDCYLON · 11-08-2018

Quote:

Originally Posted by -=Jeff=-

my best guess on the no reply is this is an odd issue and possibly not common so nobody has come a across it

Yeah I have never heard of this one either...... I don't even remember a post about this problem to the HVAC systems in 15 years of reading on multiple forums on any C4. Plenty of other issues.... GC

gbrtng · 11-11-2018

The AC clutch coil might be shorted ... disconnect the power feed wire to see if the fuse still blows.

-=Jeff=- · 11-11-2018

yeah the short (especially intermittent) are the worst to troubleshoot.. good luck

mhobtr · 11-11-2018

I have a '91 ZR1 and the wiring diagram in the Electrical Supplement for my AC is on page 8A-67-0.

According to that diagram, the correct fuse is 15A so if a '90 is wired the same as a '91, it's curious that you have a 25A fuse. That might indicate that this is a older problem that was dealt with by installing a larger fuse to eliminate tripping. This is not a good situation.

If you want to eliminate the AC clutch as a potential culprit, pull the wiring connector from the low pressure switch at the accumulator and see if the fuse blows when you turn on the AC. If it does, you need to look elsewhere.

If it doesn't, you need to measure the resistance of the clutch coil with an ohmmeter. I believe the correct resistance is around 7 ohms.

Looking at the wiring diagram, I believe you should be able to check this at the low pressure connector but there is an "AC clutch diode" in that circuit that you will have to deal with. If you read zero or very low ohms, reverse the meter probes and see if the reading increases to approximately 7 ohms.

If it does not, you will have to go to the two wire connector for the clutch which is on the side of the compressor (unfortunately under the plenum).

The AC clutch diode is taped inside the wiring harness, under the plenum, right before the clutch wiring connector. If you separate the connector, you can then measure the true resistance of the coil without the diode in the circuit. If the clutch circuit reads good, you will then need to check to see if the diode is OK. If it is, it will read zero ohms one way and open circuit the other way.

11-02-2018	#1
biggiefl Join Date: Jul 2017 Location: Ellenton, FL Posts: 8	HVAC keeps blowing fuse I took my 90 to work one day and a/c worked fine. Parked and unplugged my radar detector. Came out of work and no air, no lights, nuttin. So I replaced the 25a fuse and it blew again. What do I need to check? Aux fan not kicking in? Not sure why it would work fine and then nothing so I doubt freon. I do have the FSM but not sure if I have the part for codes.

11-05-2018	#2
biggiefl Join Date: Jul 2017 Location: Ellenton, FL Posts: 8	Re: HVAC keeps blowing fuse Wow! Everyone at corvetteforum.com always says to ask here for technical help. Guess not. __________________ 1990 Red/Gray #451

11-05-2018	#3
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,162	Re: HVAC keeps blowing fuse sounds like a feed wire that go chafed.. Do you have the FSM? best place to start. my best guess on the no reply is this is an odd issue and possibly not common so nobody has come a across it __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

11-06-2018	#4
9T1 Red ZR1 Join Date: Jun 2013 Location: Warminster, PA Posts: 78	Re: HVAC keeps blowing fuse Hello, Page 1C1-16 of the FSM shows a diagram. You could try pulling the wire off of one of the two pressure switches to "break" the circuit and narrow down where the short may be. Good luck, Bill __________________ LT5 Red/Red

11-07-2018	#5
biggiefl Join Date: Jul 2017 Location: Ellenton, FL Posts: 8	Re: HVAC keeps blowing fuse Thanks for the replies. I got the same answer about a possible wire being chaffed. Will work on it as that makes sense on why it inconsistent. __________________ 1990 Red/Gray #451

11-11-2018	#7
gbrtng Join Date: Feb 2006 Location: San Antonio area Posts: 1,179	Re: HVAC keeps blowing fuse The AC clutch coil might be shorted ... disconnect the power feed wire to see if the fuse still blows. __________________ “Buy the best example of what you want, and pay whatever it takes. That way, you cry only once.” ~ Bruce Meyer

11-11-2018	#8
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,162	Re: HVAC keeps blowing fuse yeah the short (especially intermittent) are the worst to troubleshoot.. good luck __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

11-11-2018	#9
mhobtr Join Date: Apr 2016 Location: Birmingham, Alabama Posts: 60	Re: HVAC keeps blowing fuse I have a '91 ZR1 and the wiring diagram in the Electrical Supplement for my AC is on page 8A-67-0. According to that diagram, the correct fuse is 15A so if a '90 is wired the same as a '91, it's curious that you have a 25A fuse. That might indicate that this is a older problem that was dealt with by installing a larger fuse to eliminate tripping. This is not a good situation. If you want to eliminate the AC clutch as a potential culprit, pull the wiring connector from the low pressure switch at the accumulator and see if the fuse blows when you turn on the AC. If it does, you need to look elsewhere. If it doesn't, you need to measure the resistance of the clutch coil with an ohmmeter. I believe the correct resistance is around 7 ohms. Looking at the wiring diagram, I believe you should be able to check this at the low pressure connector but there is an "AC clutch diode" in that circuit that you will have to deal with. If you read zero or very low ohms, reverse the meter probes and see if the reading increases to approximately 7 ohms. If it does not, you will have to go to the two wire connector for the clutch which is on the side of the compressor (unfortunately under the plenum). The AC clutch diode is taped inside the wiring harness, under the plenum, right before the clutch wiring connector. If you separate the connector, you can then measure the true resistance of the coil without the diode in the circuit. If the clutch circuit reads good, you will then need to check to see if the diode is OK. If it is, it will read zero ohms one way and open circuit the other way.