kuks1975

I'm hoping someone can enlighten me on the next best place to look for my electrical gremlin. I have a 1984 Targa that I recently acquired which I have now started to work through some of the items that turned up on the PPI. One of such items is the AC didn't work on the PPI. I live in Houston and it will soon be necessary to have working AC in order to enjoy the car.

I have tried the AC system a couple of times before I took anything apart and one night, it actually turned on the evaporator blower and engaged the clutch on the compressor when I tried it. It was late that night and I left it for another day because it didn't blow cold so I assumed all the bits work but it needs a recharge. The next time I tried the system, it didn't work again so I assume I have an electrical gremlin. When it doesn't work, nothing works in the system, no evaporator blower or compressor clutch engagement.

I checked the fuses in the front of the car and the number 2, 25 amp fuse is good with 12 volts on both sides in the fuse box. I swapped relays around with the horn relay in an attempt to determine if it was a relay issue and although the horn worked with either relay (exact same part number), the AC worked with neither. Next I took the switch apart on the floor and determined that the hot wire is dead coming to the switch.

So, given that I have no power at the switch but believe the fuse and relay are both good, is there any common place that is problematic in this wiring harness? I see on the wiring diagrams I have that there are two connections somewhere in the car, between the relay the switch. The wire first changes from red/white to red, then another connection of red to red. Where might these two connections be located?

I'd prefer not to take the entire dash apart and cut the factory wiring loom up if these connections are accessible somewhere without doing so. I see the loom runs from the fuse box to a horizontal bung passing from the luggage compartment to the interior of the vehicle, and I see where that comes in above the drivers feet and then runs behind the heater diffuser but I haven't found where the two connections may be located nor see anything indicating a cut or pinched harness/wire.

Or am I chasing the wrong thing and this is a result of a bad ground on the car somewhere?

griffiths

The ac relay in the fuse panel powers the front condenser blower motor.
The ac relay you want to check is the primary ac relay located in the smugglers box. The original relays had a metal cover and had a amp rating somewhere at 20 amps or greater. The aftermarket relays have a plastic cover and some have an integrated 15 amp fuse. I'd recommend using a relay with 20+ rating.

The two AC controls are in the center console.
Left **** is thermostat.
Right is evaporator blower motor.

For the AC system to operate, ignition key must be set to accessory on position or engine running. AC evaporator blower (air you feel through the center vent above radio) must be set to 1 of its 3 fan speeds.

For the AC comp clutch to engage and the front condenser blower motor to run (plastic blower box next to battery), the AC evap blower must be in position 1-3, and thermostat must be 'unsatisfied' (demanding cold), so set the thermostat to full CW (right) position.

I don't recommend running the compressor (clutch engaged) for any long time periods if the refrigerant level is low or you will damage the compressor due to lack of oil flow.

The 2nd fuse, closest to the windshield is the AC fuse. Just insure the wires in fixture are clean and tight. Aftermarket plastic base fuses tend to melt.

Issues with the primary AC relay in the smugglers box can be the relay or connections (corrosion), its common to see some melted connectors when the load gets heavy (ie. evap motor on its way out).

Check the electrical plug on the front condenser motor. If you don't have an inline fuse on the positive wire splice in a 7 to 10 amp fuse. When the front motor gets old they tend to overheat and melt down the
plastic housing. There is a Porsche fuse splice available but you can make your own.

911 AC

This schematic is helpful.

kuks1975

Very helpful, thank you! I should have time tonight to run down more of this and see what I can locate.

kuks1975

Ok, so I was able to take a look at the main relay tonight and there is 12 volts coming in on the red/white wire when there is demand. In order to get a meter on the red wire out to the switch, at the relay, I had to unbolt it from the car. When I first put the meter on the red, there was nothing. I shifted around a bit while trying to better position myself and keep the leads on a ground and the red prong, and in the process, the relay arced against the body of the car a couple of times and turned on the condenser fan for a few brief milliseconds. Regardless of what else I tried, I couldn't duplicate that again until I bumped into something when I had the leads to my meter between the red wire and the ground post on the battery. Again, it was only a millisecond of energy sent through the system while I heard an arcing sound somewhere.

Does the relay need to be grounded to the body to work? If so, why did it not work when I ran a jumper from the relay frame to the ground post on the battery?

It is the metal bodied relay and there isn't an inline fuse that I can find so I assume it is all still factory original. Is the relay just not working? I haven't been able to discover any cut, pinched or abraded wires in the harness for this loop yet so I don't think it is a dead short anywhere.

kuks1975

So, just to follow up on this, changing the main A/C relay did in fact cure the problem. Thank you for the help! Now its time to figure out how I want to upgrade the system and if it is worth having someone charge it as is, for a baseline.