Red or Black Relay?
 

Does anyone know what the differences are for these two relays besides the color and part number

911 615 108 01 standard type relay red
911 615 109 01 stardard type relay black

I have an '88 911 and discovered that all of the relays on the fuse panel are red except for the 2nd one from the rear which is black (Aux Oil cooler fan I think?).

Is there a spec difference and what is it? Is it ok to have all red or all black or does it even matter? http://forums.pelicanparts.com/uploa...1356052315.jpg

The red relay is for the fuel pump. First socket on the left side in the picture above. The red relay has a diode inside to protect the pump. All other relays should be black, but it wont hurt anything to run all red as shown above.

Thanks Nostril Cheese - This is an '88 Carrera with motronics

According to bentley page 201-10 the fuel pump relay is located under the driver seat. It is a two part relay. According to my fuse chart on the fuse cover and bentley page 971-3 the relay you mention "The red relay is for the fuel pump. First socket on the left side in the picture above." is for the footwell blowers. Thanks for the info about a diode in the red relay. Any other specs???? Amps...? Can I assume that a related component will not function without the associated relay in place? I'll begin systematically R/R each one with a known good one eventually replacing all with new black ones.
All input is appreciated.

search for "quench diode"

The diode in the relays is there to prevent the back EMP pulse.
In othere words...when the relay opens...it creates a spike in power that can cause problems...like popping sound in the stereo....or a jump in the guages...anything that a power spike of more voltage than is normally carried in the battery or charging circuit.
Even switching off a high power circuit can produce some power spikes.
If in doubt...use the red relays...no problems will be encountered...other than perhaps the relay will be a little more expensive.
The contacts inside the relays are rated for the same current.
Bob

Thank you Bob I have replaced all red with black and will see what type of changes occur.

I would replace all blacks with reds....

BEST!

Doyle