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I'm sure the heat and AC fans do the same thing. I.e. if one is working the other is, and if one is not the other is not. I'll double check to be sure but I say this because through all my testing I had no idea they were two separate things.
Another thought has come to mind. The electric bus (labeled X on the schematic) is powered by the ignition switch when the ignition is on but not in the start position. The issue could be in the wire from the ignition switch to the panel, a thick black with yellow stripe wire. This powers high current things that are shut off while the starter is cranking (including the wipers.) If this is intermittently disconnected, it would also cause the issues. An easy way to test for this would be to turn on the rear defogger and see if the bulb on the switch comes on. If it does not, I think this wire is more likely the cause of your problems.
Your wipers have some other issue, but while you are having this problem they are a least staying off, because they have no power. This further adds to the case for the ignition switch wire.
The large plugs at the rear of the fuse panel are color coded. If someone will tell us the color of the plug, that will help. Also, when removing the plug, 1: is the battery disconnected? (Ground side, please). You wil have to use a screw drive or maybe two to get the plug out of the panel. Wiggling will help. Appropriate plug numbers or letters are on the front of the panel under 40 years of dirt, I think. HTH some.
It is definitely the ignition switch itself (though he has replaced it,) or one of the connections on the thick black/yellow wire from ignition switch terminal X to terminal E10 on the back of the fuse panel, or the wire itself. It explains both his fan issue, and why his wipers don't act up when he has the issue with the fans, though his wipers have another issue as well.
Photo taken from the interwebs, though I've annotated it.
If the headlights go up and down properly while you are experiencing the fan problem, you can eliminate the ignition switch, and it reduces the probability it is the ignition switch connection. Two wires come from ignition switch X, one to the headlight switch, the other to the E10 terminal.
If the headlights go up and down properly while you are experiencing the fan problem, you can eliminate the ignition switch, and it reduces the probability it is the ignition switch connection. Two wires come from ignition switch X, one to the headlight switch, the other to the E10 terminal.
Funny you mention this because last time the fans weren't working I tried to flip up the headlights. They went up and the fans came on. This may have been a coincidence though. Usually the headlights aren't affected by what's going on with the fans.
Funny you mention this because last time the fans weren't working I tried to flip up the headlights. They went up and the fans came on. This may have been a coincidence though. Usually the headlights aren't affected by what's going on with the fans.
It may not be coincidence, and if the ignition switch looks easier to get to than the back of the fuse/relay panel, and it were me, I would start there. The momentary high current draw of the headlight motor may have heated the contact slightly, causing the other wire to make contact in the connector. Disconnect from the ignition switch, de-pin the contact with the two fat black/yellow wires, and have a look. Even if it looks ok, crimp it again before reinstalling.
It may not be coincidence, and if the ignition switch looks easier to get to than the back of the fuse/relay panel, and it were me, I would start there. The momentary high current draw of the headlight motor may have heated the contact slightly, causing the other wire to make contact in the connector. Disconnect from the ignition switch, de-pin the contact with the two fat black/yellow wires, and have a look. Even if it looks ok, crimp it again before reinstalling.
It'll be one end or the other, pick your poison.
Thanks. I'll start with the easy end, but I'm happy to know that if I have to dig around down by the relays it's a little less of a wild goose chase now.
Another thought has come to mind. The electric bus (labeled X on the schematic) is powered by the ignition switch when the ignition is on but not in the start position. The issue could be in the wire from the ignition switch to the panel, a thick black with yellow stripe wire. This powers high current things that are shut off while the starter is cranking (including the wipers.) If this is intermittently disconnected, it would also cause the issues. An easy way to test for this would be to turn on the rear defogger and see if the bulb on the switch comes on. If it does not, I think this wire is more likely the cause of your problems.
Your wipers have some other issue, but while you are having this problem they are a least staying off, because they have no power. This further adds to the case for the ignition switch wire.
Which schematic are you referring to - the one in the Haynes manual?
Oh God no. I'm looking at the one from the factory workshop manual. Do a google search for 944 workshop manual and you will be able to find a PDF to download. I've been looking at an '84 which I have separated out, but the '83 is almost the same. You should look at the '83, starting on page 916.
After you download it print it off and take the sheets down to a UPS store or an Office supply store. I had mine duplicated on 2x4 foot sheets. Much easier to read.😀!!
A year later because, ya know... Anyway, I checked the defogger light and just as you said: the light was on when the cooling fans worked and when the fans failed the defogger light didn't come on. And just like that, I think we have a winner! The fans will still come on if I give the relay box a few good whacks so it's gotta be the E10 connection at the back of the box.
I haven't been able to find the wiring diagram and was hoping for some help. I made it here: Porsche 944 manuals - Free download (uriarte.dk) but the Electric Manual should be Volume IV which isn't listed. Could anyone share it?
07-22-2023, 01:18 PM
