A/C relay Location

ruf-porsche · ruf-porsche's Garage

Does anyone know where the second relay that control the compressor and evaporator fan is located? Went to turn on the a/c today and got nothing. Checked the relay that is located in the fuse box in the trunk and that relay only turns on the condensor fan in the front condensor. Pelican website show a rectangular relay for the a/c instead of the round cylinder one. Any help would be appreciated.

Thanks

Porschedude · 03-23-2003, 06:55 PM

OK, you have a 911, but what year?

ruf-porsche · ruf-porsche's Garage

1982 911 SC Targa with Factory air

Porschedude · 08:08 PM

I have not worked on this year model, but could it be in the engine compartment left side. On my older and newer YM's, the fuses and relays are very close to the items being switched or protected.

Sorry, not much help for this year.

I'll check with my friend at work tomorrow, he has an '82 911SC.

Another problem is that it could be low on freon. When the pressures are low, the clutch will not even engage to protect the system.

Check the relays and I can guide you to bypass the low pressure switch to trouble shoot.

Keith

ruf-porsche · ruf-porsche's Garage

Neither the clutch or the evaporator blower is engaging. The front condensor fan motor will only work if I jumper the relay. Relay tested fine. According to the Robert bentley manual the seond relay must be energized in order for the condensor fan motor to work.

attach a set of gauges to the low and high side of the compressor, there is freon in the system.

LeRoux Strydom · 03-23-2003, 10:55 PM

My memory is not the best these days, but I think this second relay is located in the smugglers box next to the a/c blower fan unit. Check the Haynes manual to be sure.

LeRoux

RoninLB · 03-24-2003, 01:33 AM

Quote:

Originally posted by LeRoux Strydom
I think this second relay is located in the smugglers box next to the a/c blower fan unit.

there was one in my car's S box

LeRoux Strydom · 03-24-2003, 01:45 AM

BTW, you have checked that the a/c fuse is not burnt out, haven't you?

LeRoux

ruf-porsche · ruf-porsche's Garage

Thanks for all the help from all the posters.
Will check the smuggler box tonight when I get home from work.

Wil Ferch · 03-24-2003, 08:57 AM

While you're at it...replace the relay with the later style ( .01 last digits, as I recall instead of .00)...which incorporates an external fuse instead of having an internal diode. Used on 88+ model year.
Can someone explain why the external fuse is an improvement?....I 've checked the wiring and even though I'm *somewhat* knowledgable on electrial circuits...this has me stumped. RoninLB?... care to comment?
--Wil Ferch

RoninLB · 03-24-2003, 02:03 PM

Wil.. the diagram doesn't show why another fuse is needed.. not that I trust the 911 wiring system.. I looked at 2 workshop diagrams.. the S A/C dia., and the SC A/C dia. if I still had my A/C installed, and was curious, I'd get the evaporator motor running and start pulling fuses to confirm it's fused .......Ron

ruf-porsche · ruf-porsche's Garage

Check the smuggler box this evening and sure enough the second relay for the a/c is located in there.

I have power to the relay when the ignition is switch on and there is a constant power at terminal 30 so I guess the relay has finally gone to that part heaven in the sky.

Guess I'll order a new relay from pelican. Pelican only list one type of relay for my car.

Thanks to all the people that help me with this problem.

ruf-porsche · ruf-porsche's Garage

I order a new a/c relay from pelican parts, but while at the local rat shack I check out their relays selection and found a 12 volt 30 amp relay similar to the a/c relay in the car.

Even the marking for the wiring was the same. Price was only $5.99 so I brought it and installed it in the Porsche. Started the engine and turn on the a/c and it's working again. I will probably replace it with the relay from Pelican parts, but I wish I did this before shelling out $21.95.

Wil Ferch · 03-27-2003, 05:05 AM

Be careful:
The normal "cube" type relays may have the proper "pin" locations...and it may indeed work, but...
The "old" style relay has at least an internal diode...think of this as a check-valve if it were a piping system that doesn't allow reverse flow...this diode performs a similar job in not allowing reverse current. Whenever an original wiring system uses this type of relay, it must be important not to allow reverse current. A regular relay without this diode removes such protection. The newer style oddly has an external 16A fuse...and no-one...not even Alan Caldwell from the PCA tech site...could explain why. Alan has written a number of tech articles on A/C systems that are found in Pano.
---Wil Ferch

targa80 · targa80's Garage

The diode across the coil in a relay is to prevent relay chatter. The contacts in the relay will open when the coil is deenergized and close again momentarily due to the reverse current (collapsing magnetic field of coil) causing arching from the momentary closing of the contacts. The diode is there to prolong the life of the relay contacts by preventing the reverse current / momentary contact (chatter). I have seen circuits designed without the diode installed and they function with no excessive prematue failure of the relay contacts. I think the need for the diode in the relay would depend on the amout of current being drawn across the contacts. Most of the circuits that I have worked on have the diode installed for reliability purposes and in many cases the circuit current draw across the contacts are minimal. I do work specifically on military electronic equipment and reliability is essential so the cost for that reliability is is built into the design.

KTL · 03-27-2003, 07:15 AM

Waytek Inc. is a good source for relays. Great website and customer service. Alot like Pelican Parts.

http://order.waytekwire.com/IMAGES/catalog/215_44

According to the 74-89 Parts Reference, it looks like the A/C relay in the smugglers box is a four terminal relay. The page in the manual has a notation beneath the part number (911 615 103 01) that says "(16A fuse on top)".

I believe, based on what Wil mentioned, that you would want relay #75103/Bosch #0 332 019 155 from Waytek's page. It's a SPST (single pole, single throw) with a diode and you would only use one of the two 87 terminals? If the relay plugs into a female connector, then obviously a five terminal relay is not going to fit into a four terminal connector.

You can also check Hella's pdf chart to find the relay you need:

http://www.hellausa.com/maineng/lev1b/lev2bb/lev3bbf/catalog02/ElecProd1.pdf

Searching thru the different Hella relays, I did not come across a four terminal relay with a diode. The Porsche relay must be a special application?

Oh well, just some suggestions. Ignore my recommendations..........

ruf-porsche · ruf-porsche's Garage

Speaking of relays, everyone mention that the fuel pump relay should be red. The fuel pump relay in my car is black. I order a new fuel pump relay from Pelican when I ordered the a/c relay.

I will change it to the red relay, but since the black relay work right now, I will keep it in the glove box as a spare. Anything special about the red relay other than the color?

Hey Targa80

Did anyone of your neighbor ask if they could come over for the b.b.q. when they saw the Targa on the spit?

My wife would think that she married a red neck if she saw the P car on a spit. I know what it takes to do a body off ground up restoration on a Lotus, it takes a divorce from the first wife.

82 911SC Targa
70 Lotus Type 52 with twin webers
70 Lotus Europa
97 Isuzu Rodeo the Grocery, parts and the baby seat SUV

targa80 · targa80's Garage

ruf-porsche:

I believe the red relay is rated for a higher ampere load.

My neighbors are a little amazed at what I am doing with the car. Some have suggested that I was a little excessive in the auto hobby maintenance . I don't think anyone has ever accused me of being a red-neck, my New York City accent is to strong. The car on the spit fits into my garage with no problem so it is not an eye sour. Heck with the garage door closed you would never know there was a Porsche torn apart in the garaqe.

Wil Ferch · 03-28-2003, 04:54 AM

The red relay has the diode I spoke about...the black does not...use the right one in the right location.
--Wil Ferch

Hurdigurdiman · Hurdigurdiman's Garage

I have a 99 C2 966 Cabriolet and the inside courtesy lights over the windshield and in the lower door parts do not come on as the doors are opened. Fuses and bulbs checked and all are good. Does anyone know if there is a delay relay somewhere on the car which I should be checking on? Everything else on the car is working fine. Even the inside light can be used via a switch on the light itself. It's just a niggling little thing I know but I would like to get it working again. Any help would be much appreciated.