Don Carter

I'm trying to get my AC going for OCIC in DFW, but not making much progress, even after having a rebuilt compressor installed, and installing a new resistor pack, I've still got several issues.

This thread is about my blower fan speed issue. Several years ago after having some AC work done, the car came back from the shop blowing only low on all speeds with little if any difference between speeds. The shop couldn't explain what happened, and I was tired of spending cash on the car, so just lived with it for a while. Last week I installed a new resistor pack to try to fix it, and it made little or no difference. It was the newer type so I had to re-wire my plug to make it work with an 86 model (removed wire for pin 8, moved wire from pin 6 to pin 8 socket). As far as I can tell from all my reading and studying the wiring charts, I've got it wired right, but I still have low fan speed on all speed settings. The speed does increase some, as I move to higher numbers but 4 is still very low. On Defrost it blows very high. Here's a picture of the back of my resistor plug with the cover off.
(The story continues below picture..)



Pin layout in picture:

7 5 3 1

8 6 4 2

I created a spreadsheet to record voltage readings on the pins with the plug plugged in, and again with it unplugged (ignore column 9 on the right). Looking at the top grid (plugged in), Pin 8 feeds the blower and you can see the voltage increase with each speed, but it tops out at only 4.2v. Pin 4 feeds the resistor pack, so stays a constant 13.1v.

In the bottom graph (unplugged from resistor pack to only show voltage coming from fan switch and remove any affects of resistor pack), you can see that I get power to an additional pin each time I go to a higher speed, which makes it seem like the speed switch is working. The cell in red shows that I'm not getting the direct full power on speed 4 that I should be (my understanding is that the resistor pack is bypassed on speed 4)

Relay and power to the relay checks out as it should.

Evaporator is not clogged and has been brushed and vacuumed.

Any ideas what might be going on? I've done lots of forum searching but haven't run across anyone with this issue after installing a resistor pack.

NickT

If you unplug the fan and carefully apply 12V to it, does it run at full speed? If not the cause maybe a bad blower motor.

Don Carter

I haven't tried that. Since it runs at full speed on defrost, I figured the blower is ok.

Leon Speed

Don, the only contribution I can make is to check the resistor pack. I had a new one installed and it worked fine, then a half year later, same problem you have. I couldn't figure it out until I looked closely at the resistor pack and found that one pin (I think power supply) was a little bit loose, thus creating an interruption. I soldered it tight and since then the blower works again at different speeds.

borland

I would unplug the harness from the resistor pack and update your spreadsheet to see if the console switch is working properly. Then I'd use the WSM wiring diagram to see if the resistor pack is open circuit.

There is is a bi-metal switch protection circuit in the resistor pack to keep it from overheating should the air flow be restricted. The bi-metal switch can sometimes fail, but might be repaired without having to buy a new part.

Also, the resistor pack was redesigned but the newer part is not interchangeable with the old. My 90' S4had the wrong resistor pack installed when I bought it which was causing a blow speed problem.

ROG100

928 616 101 00 is the resistor pack that Don has in his car
928 616 101 01 is for the 94 to 95 cars.
Borland care to elaborate please?
Why will the 01 not work? Its cheaper than the 00.
Alan has already covered this and "search" is your friend.

Alan

The '94/'95 resistor pack is quite different to the earliers ones - it doesn't even mount in the plenum (due to pollen filter) - only has 4 pins used and 3 resistor elements. Speed 0 for these cars is really off (no blower) for all other models Speed 0 is just a very low speed mode (though some still allow an off mode via the blower relay controlled by the head unit off mode).

The '89-'93 model that Don has as a replacement(?) is incompatible with the earlier model only due to its pinout - it actually has the same features and mounts in the same manner. It does not have a bimetalic strip to bypass the resistance group* - instead it has a series thermal switch - if it gets too hot it just turns off (full speed mode still works via the switch & DEF).

Older versions switch to full speed via the bypass when they overheat (aka "magic blower syndrome").

Since the early version is NLA - the available '89-'93 version can be subsituted with some pin swaps in the blower socket - this is what Don has done - but he seems to be having some issues with this.

I believe the '94/'95 version could also be used - however I've never really written about this - The pinout of this model is MORE different than the others.

If Don has the '94/'95 versions - he's using the wrong instructions....

Alan

Don Carter

Roger, I thought the pack I got from you was for 89-93 originally. Sounds like the 94-95 pack is very different. Looking at the wiring diagrams, the 89-93 is only slightly different and many here have successfully rewired the plug and used this pack with success on older cars.

Borland,

I did unplug the pack and tested the voltages, those are the numbers in the lower spreadsheet.

Alan

OK Don - if you have the '94/'95 unit and assuming it fits in the plenum in the same way and has the same pinout designation (check this - I haven't looked) these are the swaps you need to do.

Note these instructions are only good for mounting a '94/'95 unit in a <'89 vehicle.

White wire stays on Pin1 (no change)

Move White/Green wire from Pin 5 to Pin 3

Move White/Blue wire from Pin 7 to Pin 4

Move the 2 Black wires from Pin 6 to Pin 2

Leave the Red/White & Red wires on pin 8 (they will not connect to anything)

Move the Red/White wire on pin 4 to pin 5, 6 or 7 (it will not connect to anything)

(its possible the pairing of the wires on pins 4 & 8 will be reversed - doesn't matter - what I listed is whats in the wiring diagrams - I think in practice pin 8 has just the Red/White and pin 4 has the Red/White & Red (functionally this is the same -> its the same red/White wire)

Alan

Don Carter

The pack I have is almost identicle to the pack I took out. 7 pins (socket 3 is empty), socket's numbered the same way and the pack mounts exactly the same way. The new pack had a cage around the coils, old one didn't, but it could have been removed in the past.

Alan, are you saying the '94/'95 pack only has 4 pins, or only 4 pins are used? If it only 4 pins, then I don't have it, I have 7.

Alan

Don - no its likely to look exactly the same but have only pins 1-4 connected to anything (you can check this with a DMM on ohms mode) if the part number is 928 616 101 01 it is for the '94/'95.

Alan

borland

Here you go. You can see what Alan was talking about rewiring the harness to fit the later resistor pack by swaping the two wire pin 6 with pin 8 and removing the jumper between pins 4 and 8.

Don Carter

I think we are talking about two different packs here. Alan is describing a pack with only 4 pins connected to anything and 3 coils (93-95?), but Borland posted a diagram showing the later pack with 5 pins connected and 4 coils, which I think is what I have. I'd have to remove the pack to see the part number which I'll do if I need, to but of course would rather not.

Roger says above that I have 928 616 101 00 (not 01), and the invoice from him also says 928 616 101 00.

Given all that, I think I have the 90-93 or 89-93 pack. I did remove the wire and female pin from socket 8, and move the wire from 6 to 8 but didn't cut any wires. I saw in an old thread where someone mentioned cutting a wire, but in all other instructions I found, like on Nichol's
http://www.nichols.nu/tip022.htm
it didn't mention cutting any wires.

ROG100

Don,
You have the right pack and not the 94 to 95 one.
In theory you should be good.
Roger

Alan

Don - Borland shows all 3 types: 78-88, 89-93 & 94-95

Check the part number on the blower relay - or if you can't do that - check with a DMM to see if pin 6, pin 2 & pin 8 are connected togeher ?

Alan