Fuse blows out on 1986: Causes anti-lock light to come on and A/C panel wont work either!

[ghr4news]

Happened the other day, the anti-lock light came on the information panel in the dash. My vette is a 1986 Coupe. I also noticed the A/C controller panel lights went off knocking off all A/C. Checked fuse and it was blown. Turns out that same fuse feeds the circuit for both the anti-lock light and the A/C controller. I replaced the fuse, car worked ok for a day, then when I went to start the car the next time, the fuse blew out again and once again the anti-lock light came on and the A/C panel stopped working. It blew out just after I had turned the ignition key to the "on" position, before starting the engine. Only thing I can think of that may have added to the problem is the day the fuse went out the first time, I had to use the parking brake; something I don't generally do cause one of these days I'm going to have to adjust the cable/hand grip. When I took the parking brake off, the parking brake light stayed on. I had to put the parking brake on and off again, do a hard release so lever could engage the switch that turns the parking brake light off. Could that have anything to do with it? The fuse that's blowing out is the "10-A Gauges" fuse. Its located 2nd from the top on the right hand side of the fuse panel. What's causing this fuse to blow?
Looking forward to your help.

 

[Sierra'sVette]

I'm having some crazy fuse issues myself. Be sure to put to your parking brake on/off in drive, not in park (for automatics anyway).

 

[ghr4news]

I'm having some crazy fuse issues myself. Be sure to put to your parking brake on/off in drive, not in park (for automatics anyway).

Thanks for the tip, but my Corvette has a 4+3 tranny.
George

 

[ecss]

Don't see any connection with the Parking Brake.

The gauges fuse provides 12 volts on a Pink/Black wire to the following items.

1)C68 HVAC Control Head
2)C68 HVAC Programmer (Mounted on firewall above gas pedal area, towards transmission tunnel
has a group of vacuum hoses going to it.
3)Defogger relay (I think it's behind the DIC).
4) Vapor Canister Purge Solenoid (Metal canister driver side. Below the headlight. Has rubber hoses going to it).
5)Courtesy Light Delay Timer. Behind the ECM and fuse box area tapped to a wire harness.
6)Anti Lock Brake Relay (Storage bin behind driver seat).
7) Header Map Light on rear view mirror.
8) Low Coolant Module (Behind bread loaf near fuse box).
9)Audio Alarm Module (Behind the DIC).
10)Lighted Vanity Mirror on Sun visor If you have a lighted one.
11)Over Drive Relay for Manual Trans. (RH rear of engine compartment next to fuel pump relay).
12) Air switch solenoid, Air diverter solenoid. Both mounted in front of engine above water pump area.
13)EGR Solenoid On intake manifold.

I would first disconnect the Interior light delay timer and see if the stops the fuse from blowing.

Then I would start unplugging the connectors at each device if you can.
Below is a picture of the interior light delay timer.


Right click and save the schematic image, then print it out if you can't see it clearly.

 

[ghr4news]

ecss: Thanks for the info. As it turns out the schematic you provided is different from the one in the 89 service manual I have. So GM did start making some changes to later model Corvettes even thought they're both C4's and just three years apart. I'll start backtracking all these connections, but your schematic still doesn't make the connection with the Anti-lock light coming on when the fuse blows, less because its all part of the info dash panel and when the circuit is cut by the fuse blowing, it then turns the anti-lock light on. So the problem is elsewhere in that circuit and I wont know till I find the source. For all I know my anti-lock system may not be the culprit.

Tx,
George

Don't see any connection with the Parking Brake.

The gauges fuse provides 12 volts on a Pink/Black wire to the following items.

1)C68 HVAC Control Head
2)C68 HVAC Programmer (Mounted on firewall above gas pedal area, towards transmission tunnel
has a group of vacuum hoses going to it.
3)Defogger relay (I think it's behind the DIC).
4) Vapor Canister Purge Solenoid (Metal canister driver side. Below the headlight. Has rubber hoses going to it).
5)Courtesy Light Delay Timer. Behind the ECM and fuse box area tapped to a wire harness.
6)Anti Lock Brake Relay (Storage bin behind driver seat).
7) Header Map Light on rear view mirror.
8) Low Coolant Module (Behind bread loaf near fuse box).
9)Audio Alarm Module (Behind the DIC).
10)Lighted Vanity Mirror on Sun visor If you have a lighted one.
11)Over Drive Relay for Manual Trans. (RH rear of engine compartment next to fuel pump relay).
12) Air switch solenoid, Air diverter solenoid. Both mounted in front of engine above water pump area.
13)EGR Solenoid On intake manifold.

I would first disconnect the Interior light delay timer and see if the stops the fuse from blowing.

Then I would start unplugging the connectors at each device if you can.
Below is a picture of the interior light delay timer.


Right click and save the schematic image, then print it out if you can't see it clearly.

 

[ecss]

Number 6 on my list is a relay for the ABS. So if the Gauges fuse blows it will disable the ABS and light the ABS indicator on the DIC.

In the schematic the ABS relay is the rectangular box bottom left in the schematic.
It shows two Pink/Black wires going to the Module Relay located in the rear storage bin where the ABS control module and ABS pump are.

When the ignition is turned to On 12 volts from the gauges fuse closes the primary relay coil. The relay then provides 12 volts from the Brake fuse which is hot at all times to the ABS control module.

Yes the 89 schematic is slightly different from the 86. The 86 used the 4+3 trans and the 89 used the ZF 6 speed.

I'm guessing the problem is the light delay timer module, the vapor canister solenoid, egr solenoid or a chaffed wire shorting out some where.