Porsche Repair: 1977 924 blower motor, amp fuses, jumper wire

Question
My son and I are putting a 1977 924 together and we have everything working great except the air/heater/ventilation system.  The blower motor is  getting some power (2 volts ~), there is nothing going to fan control in dash and as far as I can tell there is no fuses for the blower.  There is a relay but I am not sure how to test.  It appears that blower fan may be dead.  Can the contacts be cleaned or am I going to have to tear the dash apart and get a new blower?

Any help would be appreciated...

Thanks..Chris  

Answer
Hi Chris,

Congrats on the father/son combo...that can be a lot of fun.

I don't have any 924 wiring diagrams and for the 944's I only go back to '83...so for your "'77 antique", let's see if we can logic this out.

Blowers are big electricity users and normally for German cars have 25 amp fuses and relays.  For the '83 944, those sneaky engineers put in "an additional fuse board" with five fuses and hid it under the passenger seat.  If you have a red wire at the relay, it's a good bet the other end goes directly to the fuse.

Let's wait on the dash control part.

As for the relays (plural), because there are several involved, this can get complicated.  But first things first.  Your blower relay probably has terminals designated as 30, 85, 86, 87 and /or 87a.  Pull the relay and do these tests:

1.  Using a jumper wire at the empty place where the relay was sitting, jump terminal 30 and 87 while you are measuring voltage at 87.  You should get battery voltage and the fan should run.

2.  To test the relay itself, use two jumper wires and connect one end of each to the battery terminals.  The other end of the 12v jumper wire gets connected to the #85 relay prong.  The negative gets very briefly touched at #86 relay prong and inside the relay you should hear a tiny little "click".  If so it's fine.

Try this first and let me know what you find.

Dave