A/C was working great but now dead
 

Hi guys, the air conditioning in my 83 SC has been upgraded with some Griffith parts, including compressor and blower motor. It has been working pretty well in the 6 months I’ve owned the car, even this morning when I drove it to work on what’s the hottest day of the year so far in Dallas.

When I started the car this afternoon, there was nothing from the AC. The interior evaporator fan isn’t functioning and the comprsssor doesn’t appear to be running. I checked the factory AC fuse and it appears good. Any other thoughts? I seem to recall some systems having a low pressure switch, and while I haven’t checked the refrigerant levels in the system, is there a chance it could be low enough to trigger a low pressure switch? Would this stop the entire system, or just the compressor?

Is there a relay somewhere that I’m missing? Is there a test for the fan switch? Thanks in advance for your help!!

Factory AC systems for you car do not have a low/high pressure switch. If your car has an updated AC system it may have one typically located on the discharge line of the compressor (Griffiths system) to the engine lid condenser or on top of the dryer (Retroair system)

You should have two relays one on the electrical fuse panel in the front truck and the other in the smuggler box right side if memory serves me correctly.

Griffiths has a great troubleshooting page.

Great, thank you for the reference. The fuse panel relay appears gold as I swapped it with one of the others with no change. The smuggler box relay appears to be the original and I’m having difficult finding a replacement using the Bosch number. Anyone know of a replacement?

A gold relay? Normally these are black or red for a SC.

Our host has the replacement relay, 911-615-103-01, but this has been modified so the it includes a fuse and down rated to 15 amps, original 30 amps. I have noted that the new relay also does not appear to have a resistor across the coil.

The A/C relay Location thread list's Waytek as a provider.

EDIT

Sorry I should have checked the links first.

Bosch 0332019155 Waytek 75403

Here are photos of my 87 911 Carrera W-Germany A/C Relay.

http://forums.pelicanparts.com/uploa...1532142683.jpg

http://forums.pelicanparts.com/uploa...1532142719.jpg

http://forums.pelicanparts.com/uploa...1532143172.jpg

Sig... one of those relays in smugglers can get stuck (I forgot which one.) Shuts entire system OFF. Tap it a few times and magic can happen. No guarantee this is it but is very easy place to start.

Hey guys, I meant “good”, not gold. My apologies. I’m headed to autozone to pick up a new smugglers box relay, so hopefully that fixes it!

For future reference, it looks like a pretty common relay if anyone doesn’t want to wait on shipping from an online supplier. I bought it as a horn relay for a 2009 Beetle. The downside being you have to tell the parts counter you have a 2009 Beetle.

Good Morning Sig,

I'm sitting in my shop waiting on a pair of rear rotors that will never arrive.
Looks like rain will start up here around 5, so killing some time looking for a T off time.
So, let's see what we can do to get you going again.

Assuming you have a factory Behr system (2 condensers, drier in the LH front wheel well, thermostat and fan speed controls in the center console) , below is a schematic for a common SC system.

Primary power is supplied by the #2 blue 25 amp fuse located in the power panel in the front trunk, 2nd fuse nearest wind shield. Insure this fuse is good, the contacts are good. Looking at the schematic fuse 2 provides power to the primary AC relay in the smuggler's box, its terminal 30, check to see if you have power there.

When you turn the ignition key on to either the 'accessory' position or on position (engine running), the primary AC relay coil pulls its contact and you should have power coming out its terminal 87. See if you have power in this situation.

From the primary AC relay terminal 87 power goes to the fan speed switch, assuming you have a stock AC evap fan speed switch, you should have power to it, on the schematic this is the solid red wire, on the back of the factory switch the spade terminal has (+) adjacent to it .

When you turn the fan speed switch to either of its 3 speeds (low, medium, high), power goes to the evaporator fan resistor unit located under RH foot board inside the plastic trapezoid air intake. Speed to the motor is relative to the fan speed you select; sending power through the switches terminals in the schematic noted a "L" for slow, "M" for medium and "H" for high. On the back of the switch the nomenclature is "I" , "II" and "III" respectfully. The "B" in the schematic correlates to the "IV" terminal on the back of the switch which sends power to the thermostat as well as the front condenser blower relay in the power panel when either of the 3 available speeds are on.

So, taking the long road, if you have power to the fan speed switch when the ignition key is on the accessory or engine running (you can do all the checks simply in the accessory position), AND you have your fan speed switch on to speeds 1 through 3 you should have power to the correlating terminals or wires at the evaporator fan resistor unit previously mentioned, and power to the red/white wire at the evaporator blower motor located in the smuggler's well in the front trunk.

When the fan speed switch is turned onto either speeds 1-3 power from the fan speed switch is also sent the thermostat. When the thermostat contacts are "made" (contacting), such as when when the thermostat is calling for demand, you have it turned fully clockwise, then power travels through it directly to the compressor clutch wire near the oil filter by the engine, and to the front condenser blower motor relay in the power panel in the front trunk. Hence, if you have power to the thermostat and the thermostat is good, its contacts are 'made' you can hear the front condenser blower motor running, if you can't here it put your hand of the black plastic blower box next to the battery.

The thermostat's power in wire is a green white striped wire (hard to tell without good lighting). Its power out wire is solid green. To check for power through the thermostat: key on accessory position, fan speed switch on speeds 1 through 3, thermostat fully clockwise, you should have power at the green/white terminal and power coming out of the solid green. If not, then the thermostat is suspect to replacement if no power out.

To check for power to the compressor clutch, once again, key on accessory position, fan speed switch on speeds 1 through 3, thermostat fully clockwise, check with test light or VOM at the AC power wire's male spade terminal in the funky translucent plastic sheath near the oil filter. If you don't have power back there then work backwards to check for power coming out of the thermostat as discussed in the previous "stuff" above. If you have power at the this power wire and the compressor clutch is not pulling in when connected then check the resistance of the compressor clutch coil. Using an ohm meter you should have about 3 ohms nominal between the compressor wire and the compressor body as ground. If no resistance and the wire connections are good then you have a broken coil wire inside the coil, if the resistance is much higher then you have a bad coil as well. If your system has a pressure switch between the AC power wire and the compressor clutch wire then check for power coming out of the pressure switch, you can also do a continuity check on the switches wires. If no power coming out of the pressure switch then either the switch is shot or your system pressure is too low (refrigerant loss).

So, start off with the basics above, check for power starting at the primary AC fuse # 2 and work your way down the system. You could work it backwards, jump around here or there, however its always good to take the long road the first couple of trips.

Griff

PS. if I made any mis-o-spellings, grammar errors, confusion in steps, its a Saturday.

PSS.. Harold's 30 amp relay is preferred over the ones with a 15 amp fuse built in.
My suggestion is always use a relay of this amperage or higher.


http://forums.pelicanparts.com/uploa...1532184899.jpg

I have 83 SC. One relay in the smugglers box. This was the issue when my AC recently stopped working. I tested the relay per couple of YouTube videos and it was not good. After I played around little bit somehow it started working again. Maybe your relay is stuck also. I am thinking I should buy new relay anyways just in case it does it again. Does anyone know where to purchase heavy duty relays. Plastic ones from China are junk.

Well, I followed the path of least resistance/intelligence and bought an $8 AutoZone replacement relay for the smuggler's box which didn't solve the problem. I went through the next steps and eventually pulled the blower switch from the center console.

In technical terms, it's fried. All wires show signs of heat damage, and the switch is was so brittle from heat that one of the posts broke off when I was examining it. I have ordered a new switch, but any thoughts as to what would cause the heat damage? I suppose someone could have bypassed a relay at one point in time, but I don't see any evidence of that in the wiring I've examined.

Would it overheat simply because the switch is bad? I've only owned the car about 6 months, but I pretty much run the A/C whenever I drive it. This has included two 6 hour road trips. In that time, I've never smelled smoke or hot plastic/insulation. I suppose it's possible the damage occurred at some prior point, but I'd love to make sure prior to frying another switch.

Thanks in advance for your thoughts!

The primary load is the motor, the switch contacts see a lot of amperage.
The secondary load are the 2 resistors in the fan speed resistor unit.
The switches do fail over time simply from the load, and how old is your car?

First, you can test the evaporator motor by running leads off the battery our using an alternative 12v power source. Let the motor run for 15 minutes, if it continues to run that is a simple test. Next, if you have access to a simple inline amp meter (old school analog, 0-20 amps), see how many amps it is drawing after 15 minutes.
Typical amp draw a full speed is between 12-15 amps, the load will be higher when the evap motor and blower wheel are in the box as opposed to out of the box.

Second, you can inspect the fan speed resistor unit's 2 contact point sets, they bend as heat from the resistor springs increases to turn things off. Here, Discseven had a thread on the topic, Karl. please post the link.

Are you sure about that? Surely putting the fan in the box restricts the air flow which increases the motor RPM and draws LESS current.

More resistance against the fan blades, due to restriction, means that the motor will draw more amps attempting to spin at its max rate, correct?

Heno Cefnder John across the pond in Sussex UK. Your cousin here in Sussex, NJ.
Next time i'm visiting old grounds in Wales I'll swing back your way
and say hello.

Where did i get that crazy statement from? Probably years back when we observing the fpm of the stock bosch motor vs. another in the box, and we were running rpm tests on the motor and wheel out of the box; checking amp loads. I think we still have the setup on the work table playing with some funky Neodymium materials (bugger stuff loves to oxidize). I'll run the tests again for you if needed. However, I recall its matter of mass as well as the distance between the blades and walls of the box. Akin to taking the old shop vac and putting your hand over outlet and the rpms rise and the motor screams like a banshee (Irish woman imitating When Sally met Harry). Or is it more like a fuel pump that suddenly is pushing air rather than petrol? Anyway.

^ You'd be more than welcome. We'd have lots to talk about I'm sure!

Back to the fan thing. It seems backwards I know, but restricting the flow gives the fan less work to do as there is less air to move. The reason the shop vac screams when blocked is because the motor is running faster with less load. Less load is less current drawn.

Fundamentals of HVACR: Understanding Centrifugal Fan Motor Performance

No,Not correct. Its the opposite. Fluids 101

Yes, what Johnny H says. You restrict the inlet air then the work that the fan is designed to do is less. My Concept rower demonstrates this whenever I use it. Open the air and cal's, watts, etc goes up. Ahh, good ol fluids but I think that was either 201 or 301 for me.

Yeah, It was fluids 201.

I'll eat the crow on that. Ran test again this morning and amps dropped with motor and wheel out of the box..... logically.

More humble than a round at Carnoustie in Dundee .