The heater fan speed on my 1993 Saab 9000 has reduced from 4 speed to maximum only. Is it a major strip of the dash to replace the unit or is it easily accessible? The usual backroom expertise would be greatly appreciated.
You need a new blower resistor pack, about £40 from Saab. It's located on the blower housing, passenger side, under the bonnet on the bulkhead. Just a couple of screws to undo, and you're done, 5 mins tops.
With minimal information and no circuit diagram it is only possible to guess. But if the first 3 positions dont work and the 4th position does, (at high speed) I would be looking for a common point of failure. Depends how they wire the resistors, but if the Resistor pack is openable look for burnt out wiring or a common burnt out resistor.
Replacement high wattage resistor about £1! Try Maplin or RS.
pmh (was peter)
Some cars ( I am thinking specifically of early 90's primeras) do not have physical resistors for this function but a pcb with the tracks themselves providing the resistance. There is a fuseable link on the card that goes, when this is repaired it will work again. It is up to yourself what chance you want to take,repair with a blob of solder, piece of fuse wire, pukka fusible link, the choice is yours but if you go for the blob of solder do not come crying when it goes on fire. Don't know if this applies to Saabs though.
I can confirm the symptoms do point to the resistor pack.
After some web research I just repaired my 91 9000 CD with the exact same symptom. The resistor unit is on the US passenger's side, beneath the false bulkhead (plastic cover just behind the firewall). Mine was gray, about 3" long, 1" wide with a rounded top and bottom. I believe it is mounted on the side of the air ducting just below the AC evaporator.
You can buy a new part- I've found them as cheap as $55 from eeuroparts.com (Connecticut, USA). However after taking mine out and testing it I thought I'd try to repair it. I went to a local electronics store looking for 50W resistor of 0.22 ohms which is what I read on the web was required. This was not the case. Those power resistors are huge and nothing like the original part. On mine there was a gold colored "resistor" with a green stripe and a label of 109C. It is actually a thermal fuse or thermal cut off (TCO) and cost $1.69. Part number NTE8108, also replaces ECG8108, SK859. It gets crimped on with the crimp rings supplied. I bought mine at Active Electronics, www.activestores.com . They are the US subsidiary of Future Electronics. www.futureelectronics.com .
So far everything has been working fine again. If the TCO blew because the blower was drawing too much power I guess it may go again soon and I'll need to replace the motor and the fuse. I might also try a slightly higher temperature TCO. I don't see how another 5C could hurt and it may provide enough margin to keep the blower going. I'm not looking forward to digging deep into the system to pull the blower, condsider replacing the heater core etc. I hope this helps.