Erik Juhl

I am trying to correct my windshield washers not washing and I think the problem is the intensive washers relay. The headlamp washers work(though they tend to stay open and leak out completely) so I feel that the pump is probably ok. I don't think I hear the pump running when I try the windshield washers so I suspect the relay. Can anyone tell me what tools I will need to test this relay or alternatively, how I can confirm whether or not the relay is the issue via some sort of short circuiting? Thanks in advance.

dr bob

Erik:

Before you get deep into electrical stuff, some reminders:

There are three separate washer pumps on the car-- one for the regular washers, one for intensive washer fluid, and one for the headlight washers. The regular washers and the headlight washers have separate pumps located in the right front wheelhouse. The intensive pump is by the intensive washer fluid tank, base of the windscreen on the drivers side of US cars. Each pump is diagnosed separately. The fluid systems for the regular and the intensive washer fluids are separate into the hood, where they are connected through a couple 'Y' fittings and four check valves.


By far the most common failure mode for the 2 washer systems in the hood is clogged or corroded check valves. To see if the pumps are working, you can carefully remove the two hoses that attach to the hood plumbing there on the right side of the hood, just inside the hinge. Put the hoses in a cup, and activate the washers to verify liquid flow into the cup. If you have flow, go after the check valves in the hood. No flow means you have a pump problem.

To do a relay bypass, make a jumper out of a short section of wire, with male 1/4" spade terminals on the ends. Plug the wire ends into 87 and 30 (in that order...) to simulate a closed relay. If the pump now pumps, you have either a bad relay or a bad switch feeding the relay.

This jumper should always be in your tool kit in the car, by the way. It's the emergency fuel pump relay bypass that will get you home in a pinch.

If you have pump flow but nothing out the nozzles when connected:

The washer check valves are not expensive. Dave Roberts sent me a pack of four, some new hose, the 'Y' connectors, and for me a replacement fitting where the hoses go up into the hood. Not at all expensive, and the new non-yellowed/browned hose helps with the appearance there under the hood for sure.

Remove the two plastic access plugs under the washer nozzles (one has the hoses and heater wiring passing through.) Attach a piece of string or wire to the drivers side hose, and disconnect it from the nozzle. Disconnect the passenger side nozzle, and pull the hoses and the end of the string out through the passenger side hole. Keep the driver side end of the string tied off so it doesn't get pulled through.

Assemble your new hose, check valves and 'Y' connectors to match the old parts, using small wire ties as hose clamps on those little connections. Note the direction of the check valves when assembling. Pull the new assembly back in using that fish string, attach to the nozzles, and you are pretty much there.


Hope this helps!

Erik Juhl

Excellent information! Thanks for the help.

PatrickP

Hey Dr. Bob!

This is one of the jobs I also will need to tackle in the relatively near future. Thanks for the detailed explanation. Wish I could reciprocate and pass on my "extensive" 928 maintenance knowledge. Sadly, to date, no one has asked how to change the air filter!

Moss928

Relays can be tested easily by switching. Choose a non critical relay that you know works (horn etc,.) with one in question. Make sure they have the same part number.

You can find information/charts on relays here: http://www.928gt.com/

Adrian

Dear Moss,
Before attempting any work on relays I highly recommend you have the wiring diagram laid out in front of you.
However in this case the fault is 80% going to be the pump. No pump running, pump has failed.
The pumps fail internally the fluid leaks through them. Common problem in colder climates when the fluid freezes and cracks the internals of the pumps.
You can mess around with checking relays, I do not advise swapping relays because I have seen far too many mistakes made in this area. With the wiring diagrams you can remove the relay and jumper the contacts however it is just as easy to remove the conenctor to the pump and apply 12VDC to it and see if it cranks ups. It should also be noted that there are two possible faults with relays. One the relay coil itself is failed and it will not energise or more commonly the contacts are burned out or welded together. One will ensure an open set of contacts when you want them closed and theother a closed circuit when you want an open or a contact change.
Ciao,
Adrian
911C4

PS: If you wish to save money when replacing these pumps. Use the Audi/VW version. Same Bosch p/no number. Much cheaper and the same pump. The most important item to remember is the mounting gasket. This must be renewed. If this is damaged the tank fluid will leak out from around the pump mounting.

Erik Juhl

Adrian,
Thanks for the parts tip. I always like to hear about alternative(and acceptable) cheaper parts. For example, the porsche horn relay on my 84 lists as $12-$15 on pelican and 928intl, but my local parts shop had the VW equivalent for $5! Has anyone put together a list of acceptable-alternative-cheaper parts? Such a person should be praised and adored.

jim morehouse

On parts, is anyone aware of a source that translates the Porsche part number to the Bosche (or vw,audi) part number? If not, myabe we could start building a 'database' of our own?

Jim

Randy V

Great idea Erik and Jim. If you all can come up with a standardized format for interchangeable 928 parts, I'll see if John D will give us some server space for this list to reside on.

Let me know how you want to proceed.

Erik Juhl

Maybe we could just start a new topic asking all owners to submit their list of known interchangable parts. If the amount submitted is very little, I wouldn't bother formatting. But, if the other owners have lots of data, then maybe we format it to follow the porsche parts PET. Could an Admin maybe make a topic that is always on top that asks for these submissions?

Randy V

I guess I could start a new topic, then post a reply once in awhile to keep it active, but this doesn't seem to be an elegant approach.

Any other ideas gang?

Adrian

On the relays you will find "sometimes" the Vendor and Manufacturers part number. Bosch and Porsche. On the silver relays this is normally quite easy. Simple examples are fog light relays. Even the black plastic cased Hella versions work. The more complex relay systems (the dual relay packages or the relay/regulator packages) you need to take care but the vast majority will be found in VWs and Audis. Audi being the better source for the more complex stuff.
This is where the wiring diagrams are needed. Also remember that the vast majority of relays have the contact set up on the side. Always check that the new relay matches the old one.
Ciao,
Adrian
911C4

PS: Some of us are slowly building a database of such items. It takes time because I will never tell anyone that something works unless I have personally tried it first. My book on the 964 which is now finished and awaiting publication has these things throughout. Much is usable on all Porsche models from 1978 model year and up.

Randy V

That's great Adrian - let us know when you release that cross-matched parts index.