328 AC cabin fan not working. Very early 1986 328. Fan worked last year but doesn't now. 1) Fuse looks good. Fuse is hot. 2) Removed relay -- no hot or keyed hot 3) From known hot to what I think is AC switch relay slot shows 12.7 volts no matter position. If I check heater similarly shows 12.7, but at full ON shows 13.2 volts. 4) Should add that I never use AC, only check before shows, so conceivable that it never blew full on. Unfortunately doesn't work at all now. Does anyone have a legible schematic which could help? I have a blurry .pdf one I bought many years ago which is pretty much useless. Also looking for how to proceed. Thinking running a hot jumper (fused of course) into relay plug-in to test motor. Suppose should check relay slot to motor plug to confirm correct slot if I knew wire color. In addition relay receptacle not making sense. In addition to no hot, wire from AC fan switch goes to #30 relay tab. I would expect that to be hot. Owned car over 30 years, so sure nothing messed up recently. Looking for some guidance from someone smarter than me (which should be pretty easy to find) THANKS in advance!
You need to replace the reostat located in the duct under the dash in the center it a plate with the reostat solders on Here is a pic with the part number you can get them on e bay for $2.00 it also controls you variable fan speed for the AC Image Unavailable, Please Login
Does the AC cabin fan: 1. Only work at full speed? (Probably caused by a bad power transistor as mentioned.) or 2. Not work at any speed? (More likely a bad fan motor or loss of +12V to run the fan system.) See if this is a better quality pdf of the 1986-87 US 328 wiring diagram 440/86 than what you have: https://www.dropbox.com/s/vsxcnaheq1igub4/328 US 1986 1987 wiring diagram book 440_86.pdf?dl=0 Fig 8 item 105 is the (AC cabin fan) evaporator blower and item 106 is the power transistor (that is involved in all fan speeds except full speed).
AC fan does not work on partial or full speed. Assuming the partial is controlled by the transistor, but assumed full was through the relay. Again no hot or keyed hot to relay confusing. THANKS guys for suggestions. I'll take a look at the .pdf and also check out the transistor. If I throw known hot to fan, that should tell me if it works or not. Will report back.
Sounds more like you've lost +12V power to the whole HVAC system. My recommendations: 1. Confirm the power windows work with the key "on". This verifies that relay u is working (and relay u is what operates relay p). If your power windows don't work = try a different ...113 relay in the relay u position. 2. Check fuse #17 "Air conditioning system" 3. try a different ...113 relay in the relay p "Relay for Air Conditioning operation" position. 4. Unplug and inspect the white w connector on the fuse relay-panel (the w connector is the single vertical connector). The large MN (brown-black) wire in the 2nd down for the top position is what runs the HVAC system. When the key is "on" = this MN wire should be +12V. (If you do have +12V on this wire with the key "on", but still no blower operation = EEEECK!) No, there's no "hot" at the AC fan relay terminal 30 nor terminal 87. The way it works (when it's working correctly ), is that one terminal of the AC cabin fan always has +12V on it whenever the HVAC system is "on". The other terminal of the AC cabin fan relay is either: 1. connected directly to ground by the AC fan relay when full speed is requested (so the fan runs full speed), or 2. is connected to ground via the C-to-E path in the power transistor, but the (large) amount of current that flows thru the power transistor (in the C-to-E path) is set by the speed knob which controls/varies the (small) current that flows in the B-to-E path of the power transistor (this varies the fan speed). This arrangement is known as "common emitter".
HUGE Thank You to all who responded. @SteveMagnussen, followed your step by step. Low and behold replaced relay P, and it works! I was checking relay V, which obviously was wrong! Concours coming up in a week and a half, and we usually score well so definitely needed it fixed. Again THANK YOU!
You're welcome, and glad that you got it sorted (I appreciate getting the feedback of your findings to add to my "gut-feel probability database" of what can go wrong). Relay p does not have an easy life -- the total current to run the HVAC system is a large percentage of its maximum current rating (and is even higher that the current to run the CIS fuel pump -- and that's troublesomely huge! ).
