A/C Relay Question - front condenser fan inop
 

Turned A/C on for the first time this year and performance was not good - I appear to be low on refrigerant. Rather than evac and recharge I opted to try topping off the charge using gauges. While working on the system I noted that the front condenser motor was not engaging. Unplugged and tested motor by direct connect to the battery and it works fine. Swapped #1 relay on the fuse panel and no change - still inop. Everything else appears to be working (compressor, evap fan and fans on aux condensers (2) in there rear wheel well). My question is does the A/C relay in the smuggler's box control the activation of the front evap fan relay and could that be the source of my fan problem?

Front condenser fan is fuse protected. I checked that fuse and all other fuses on the panel and all is good.

I think that is the case. However, I do not have enough experience to say for certain.

You can download the Bentley manual from this site and look up the wiring for your application.

Manuals

From the SC bentley: The AC temperature switch controls the compressor clutch and the relay for the front fan.

I have an 81 SC and I do not think I have a relay in the smuggler's box. My pal's 89 930 does have a relay in the smuggler's box and this would be the same system as the OP's car. Hence the suggestion to look at the Cannell Bentley manual.

If your SC doesn't have a relay in the smugglers box,its not factory A/C.
Howard

Fuse 20 powers the relay for the aux fan. Try rolling or replacing that fuse,they will corrode,use only copper element fuses. No Aluminum !!!!! The relay for the aux fan is seperate from the system relay in the box. That one is on the relay panel. electrical diagram is here on this site.
Howard

OK - Cool. You are probably right. I never had issues with the evap fan working. I do not remember seeing it but will do a visual check asap.

I had to replace the relay in smuggler's box on my '84 when the front condenser blower didn't work.

Mr. Thomas,

Follow Mr. Freeman's lead on this one.

Also check the connector to the fan. Mine was bad.

There is a fused update harness for the front condenser blower motor. If you don't have it, it is a very good idea. It is available from out host. Part number OEM-911 612 077 00

If you do have it..check the fuse.

Got it and have checked the fuse. All good there. Thanks!

The fuses all look OK but I do have some Alum that I will replace with copper. I need to check the wiring to the fan relay socket.....had battery replaced recently and something could have been pulled loose.

I have not opened up the smugglers' box yet to check the relay (I've ordered a new one already as I did not replace it when I did my A/C system 2 years ago. On drive back from a trip this AM I had the A/C on to test function and I started to get a hot electrical smell so I shut it off. All of the wiring, fuses and relays outside the smugglers box look OK so I am anxious to see what going on in there.

If you are getting power all the way to the fan motor, you may want to check the inlet side of the motor housing as well as the flow through area behind the bumper. The photos show the culprit I found a few years ago, unfortunately, my fan motor had self destructed long before I discovered the wad of paer inside which was binding the cage fan.http://forums.pelicanparts.com/uploa...1331928367.jpg
http://forums.pelicanparts.com/uploa...1331928381.jpg

No update yet. Smugglers box A/C relay arrives tomorrow and I did not get a change to work on it this weekend. I've now got two projects on my to do list. Fixing the A/C and installing a driver's side fender oil cooler from Elephant Racing that arrives today and was ordered prior to the A/C failure. Hoping to lower my oil temps this summer by 15+ degrees.

The smell was reminiscent of the melting A/C #1 fuse issue that I had several years ago before the Griffiths upgrade so that was the first place I checked and the fuse was OK. At that time, IIRC an overcharged system was part of the problem as an evac and proper charge at the dealership solved the overheating fuse issue.

As a reference, I'm adding a link to this thread with good info on the A/C relay in the smuggler's box. My new relay with the external fuse arrived yesterday, according to this tread, was introduced with an external fuse vs internal diode in 88+ years.

http://forums.pelicanparts.com/porsche-911-technical-forum/103419-c-relay-location.html

More thread reference info. Link to A/C wiring diagram:

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_AC.jpg

15 amp ac relay?

So... terminal 87 on the ac relay in the smugglers box is "suppose to" support:
a) an evaporator blower motor that draws 12-15 amps, depending upon conditions , plus
b) a compressor clutch coil that draws 3-4 amps, depending upon conditions,

At this point we are consuming 15 to 19 amps, depending upon conditions, and then we add:

c) other circuit items that consume amps, which include all wiring to things like the blower switch, bimetallic switch, thermostat, dme, front condenser blower motor's relay coil, compressor clutch, and the 'conditions' or integrity of the wiring as a whole and at each junction such as terminal connection or splice. Conditions can include things like the integrity (corrosion, effective contact surface of a terminal, number of complete strands intact) and temperature, air density, efficiency of a motor, etc.

Food for thought side notes:
i) I recall a very knowledgeable and experienced tech whom installed a blower motor in a clients car. He said the AC relay immediately failed after the installation. I asked him what amp relay was in the car and he told me 'factory original'. I suggested replacing it and checking the amp draw on the motor, and to 'run it over night and see if dies' before releasing the vehicle to his client. Well the client picks up the car, drives 1300 miles south and along the way the ac blower stops working. He visits another shop and the tech there inspects the relay, said it failed and it was a 15 amp relay. He also tests the evap motor and "feels" it might be drawing a bit more amps than normal. He installs a new evap motor just in case and replaces the 'factory relay' with a 25 amp relay. Client drives away happy. We get the evap motor back and test it. Its normal. The tech whom originally installed the evap motor calls us and demands we reimburse him because his client had to pay the other tech 1300 miles away. And he insists he installed a 'new factory relay'. Another story. Anyway, we further test the questionable evap motor on a bench for 6 months running in variations of 1 hour, 3 hours and 8 hours of continuous use. No problems. We run it in a car for 3 months using a 15 amp and 25 amp ac relay. No problems. Its a normally adjusted and happy motor. Moral to the story.... "conditions can be different in different cars". Use a 25 amp relay.

ii) A few months ago we finished a respectable client's ac upgrades. We test drive the car with the client, stop to chat, and he's happy with the work. He climbs in the car and turns the key and it won't start. OMG! I feel the anxiety of expectations face me. What now? But I'm lucky. He is very patient. He asks "so, what did you think?". OMG, where do I start. So I think about all the possible places we worked that might affect ignition and fuel supply, and frantically go over the car.
Check this. Check that. Wiggle this. Wiggle that. All wires look good. Suddenly the car starts. He says "So. What did you touch?" I tell him all the points and we ponder. Then, suddenly, thanks to having a mind like an elephant and total photo recall, I say "You know, my 87 did that before. Won't start after its warm. Hmmm, doubt its the coil.... hmmmm, Hey I got! DME Relay! Happened to me." "You think?"
"Well, I'm not an expert but its what I changed and it fixed the problem". So he drives away. Takes the car to his full tech. And the tech replaces a fuse. He drives away. A week later he calls me and it won't start again. I tell him "try the DME relay, alot of techs tell me they keep spares in the glove box". So he replaces the DME relay and advises me over the next month that it fixed the problem. Moral to the story.... statistics can be your best approach to solving car problems.

iii) Yesterday a tech calls and says a client's SC ac system is not consistent, the evap blower motor and system shuts off on its own sporadically, it has a mind of its own.
The tech and I go over the upgrades the client's car has and we ponder circuit points to check. 3 hours later the tech calls back, "You are not going to believe this, the relay is good however the yellow wire which goes back to the starter was loose at the starter". Moral of the story....."Hey, I learned something today!"

Griff, great info. So you are suggesting using a 25amp vs 15amp relay in the Smuggler's Box? If so, being more of a banker than an electrician, is that as simple as changing out the fuse on the relay or do I need a relay that is engineered for 25amps? Note, mine is stamped 12V/15A. Here are pics of my new OEM Porsche relay obtained up from the local dealership.

Thanks!
Mark

http://forums.pelicanparts.com/uploa...1332433488.jpg

http://forums.pelicanparts.com/uploa...1332433541.jpg

Mark,

Here is my opinion:

If you toasting a relay and its not because the relay is worn, then something (component or a circuit) is drawing more amps than it should.

First you want to determine if the circuit has good integrity (switch contacts, terminals, wire).
If you have a failing switch, poor terminal contact or frayed wires, fix them.

Second, check the individual components (motors) to insure they are not drawing excessive amps; meaning above what they are rated to consume. Replace those that are, such as a failing front blower motor or whatever. We had a client last month that kept popping a fuse, it ended up to be a brand new Spal brand blower motor on an add on condenser (even the best can fail at times).

A simple inexpensive amp panel meter comes in handy to trouble shoot problems

Third, if the relay is not sufficient enough to support the demand, such as having 19 amps of clean demand but only having a 15 amp relay, then replace the relay with a 25 amp. A 25 or 30 amp "AC" relay is very common, get one with the same pin outs. You don't need a relay with a fuse but you could simply put an inline fuse off of terminal 87 if you wish.

Griff