Repeated blower motor resistor failures

[bobfope]

First off, yes. You may well have a worn motor
that's taking out your speed controlling device.

But, first - There are two climate control systems
available in these cars. The basic MCC and the more
sophisticated ECC, so, it would be helpful to start
with the basic question: Is your system MCC or ECC?

MCC ( Manual Climate Control ) has a 4 speed fan
control and uses an actual set of resistor wires.

ECC ( Electronic Climate Control ) has a fully variable
fan speed control, includes a switch marked "AUTO"
and uses an electronic "resistor" to control fan speed.

As there are different diagnostic steps for each system,
please let us know which one you're dealing with.

Thanks for your response. We definitely have the MCC system and I have a wiring diagram for it. As it stands now we do know that the evaporator is leaking refrigerant and will have to be replaced to fix the AC problem. It's reasonable to suspect the evaporator is plugged up and restricting airflow (The motor turns on the highest setting but the air volume is low) that allows the thermal fuse on the blower resistor part to open. To get control of the airflow in the system (and before doing the major job of tearing the cabin apart to replace the evaporator) we're going to replace the blower, clean out the ducts and replace the cabin air filter. I'm hoping that we can replace the thermal fuse on one (or both) of the two blower resistor parts (#9137937) I have already bought instead having to buy a new one in order to gain multi-speed control of the new blower motor, knowing I can't use the AC until the evaporator is replaced. Do you happen to know what the nomenclature is for that thermal fuse and where I can get them?
Do you think we are on the right track? Again thanks for your help and insight.

[RickHaleParker]

Do you happen to know the nomenclature and how I can get another one of those thermal resistors?

Thermal Fuse not thermal resistor.

You can get one at just about any electronics supply store. Your need 215°C - 230°C (419°F - 446°F) $1.50 at Radioshack.

The green part is a resistor pack. The silver part is a replacement thermal fuse.

[bobfope]

Thanks again for your reply, it's been most helpful. I've ordered a couple of those replacement thermal fuses and hopefully I'll be able to save a couple of those expensive blower resistor parts.

[BEJinFbk]

The three lowest speeds pass through the speed switch, the normally closed contact
of the Speed 4 ( Full Voltage) relay (2/24) and the resistor pack. You may wish swap out
the Speed 4 relay and inspect your speed control switch for signs of possible meltdown.

Here's a diagram that may be helpful in assessing your MCC:

95 850 MCC Wiring Diagrams.pdf

(450.04 KiB) Downloaded 1772 times

[bobfope]

Once again, thanks for your input. I have a wiring diagram for the MCC system from the Original Technical Publications DVD I bought for about $45 which was described as the "best", but the one you sent is way better to understand and deal with. Can you tell me the name of the book it came from? I definitely will swap out the speed 4 relay and the speed control switching if it looks like it's been compromised. Thanks again.

[RickHaleParker]

Can you tell me the name of the book it came from?

Volvo wiring diagrams.

[BEJinFbk]

Can you tell me the name of the book it came from?

Volvo wiring diagrams.

TP3907202 850 1995 Wiring Diagrams

[abscate]

Bob

You are local to ALBANY Volvo fest so when you are ready to tackle those big jobs, give us a call.

You need to replace that filter every year or so in our climate of leaves, pollen, and corrupt politicians.

It Tried sourcing a thermal resistor on My VW , half-heartedly. Maybe mouser or DigiKey will have it. Are there any manufacture marks or codes on the thermal resistor

[BEJinFbk]

DigiKey is a great place to start:

https://www.digikey.com/products/en/cir ... -fuses/146

Love those folks!

[bobfope]

Following the link to Digikey, I tried to find the replacement thermal fuse that is on the aftermarket Meyle 5008400001 blower resistor I have, and I couldn’t find it. I would describe the fuse I have as being copper in color with two bands of marking, “216KR1” and “C5301”. I have tried searching on these markings in various configurations and have not been able to find any corresponding part.
At a recent posting, RickHaleParker said the replacement could be found at Radioshack

https://www.radioshack.com/products/rad ... ector-fuse

with broad specifications 215°C - 230°C (419°F - 446°F) . I have ordered this part (but haven’t gotten it yet). However, I’m confused as to how to compare it against the actual part that I have as these thermal fuses have several specific specifications.