W210 Blower question

[dukegrad98]

Alright, I've been reading threads for the last 20 minutes or so, and I may know my problem. Before I go down rabbitholes trying to fix things, I figured I'd ask the experts here.

Today my AC blower on my '98 E sedan decided to be intermittent. It sounds like it's "rev-ing" up and down. The cabin controls look right -- temps set, fan speed indicated, no econ light, etc. In fact, vent temperatures are probably colder than I've ever seen them on this car, with 95-degree ambient temps here lately.

Occasionally the fan just cuts out and there's no airflow. The blower almost never comes on when I start the car (half a dozen tests now, at least five with no fan at start-up or thereafter). If I use the manual fan speed control and punch it up to max, it seems to always start up the fan and blow consistently and hard. After this jump-start, if I hit auto, sometimes it will then self-regulate, and sometimes it will pulsate and/or cut out completely.

Am I in for a W140 blower regulator replacement? Or is this something else? Any expert tips appreciated -- it isn't going to get any cooler around here for a good long while!

Cheers, John

[dukegrad98]

The actual blower fan/motor seems to be intermittent -- maybe I wasn't clear. Sometimes it won't come on at all, at least automatically. Sometimes it comes on and is OK. Most of the time it seems to be stuttering. I can always make it rush air if I manually put the fan speed to its highest setting. If I go back to AUTO, it's hit or miss, stutters, and sometimes cuts out altogether. It never comes back on of its own, without my provoking it with manual fan speed override.

So if that's not the regulator, what do you recommend? Gotta have some cool air this time of year!

Cheers, John

[Matt L]

Regulator failure usually results in a fan that will not run on maximum speed, however I am sure that there are other failure modes.

[TMAllison]

I believe if you look at the actual values when operating correctly vs with fan speed at max when not, that you will see the voltage reported on #10 is not plausible while the fault is occuring (ie: 6volts reported and no air movement).

Mine has been intermittant for a year or so; oftentimes I can reset it by turning the CCU off and then restarting the engine (wasiting some of my 200k lifetime starts). Sometimes not. Mine does this more in the winter when heat is needed which is a lil easier to live with compared to no cooling.

I'll be perfroming teh W140 reg retrofit sometime soon.

[dukegrad98]

I went out for further diagnosis/testing this evening. At this point the intermittent behavior is gone and I have no AC blower fan at all, at any setting of temperature or fan speed.

Does this narrow down my diagnosis some? I checked the fuses (#4 and #7), and both are fine. Is there any other relay or fusible link? Or am I back to the regulator?

Thanks to you guys with lots of experience on this car. Gotta patch her up before a road trip in two weeks! I'm going to look up how to run the control unit diagnostics, which I couldn't remember while I was out there. I'll post back any relevant numbers.

Cheers, John

[dukegrad98]

So I ran the diagnostic tools. I get error B1234 -- sun sensor, which I know I can ignore. While reading out these codes, the recirculation button light was blinking constantly. Not sure what that means...?

Then I took two readings of the first eight values -- one right at startup (left number) and one three minutes later after driving a few blocks (right number):

#1) 32 32
#2) 33 30
#3) 19 18
#4) 19 18
#5) 17 07
#6) 85 85
#7) 14 09
#8) 55 33

For the first set of numbers, the diagnostic says my freon is low. Dubious, as I added some several weeks ago, and before the blower went out the car was as cold as it had ever been. I could add some more but don't want to overcharge. Is there a safety switch for low freon? If so, I wouldn't hear the compressor kicking on and the evaporator hissing a tiny bit -- I think those switches are designed to cut out the compressor, not the blower fan.

For the second set of numbers, the diagnostic says my duovalve or mixer flap is stuck. I checked out the duovalve back when I had low freon and it was fine at that time.

Nothing about the blower motor, which at this point isn't running at all.

Does that info help you guys?! Thanks again!

Cheers, John

[Matt L]

No action is easier to diagnose than intermittent action. See if you're getting voltage on the control wires of the regulator.

You didn't post the reported control voltage. I think that's #10.

[dukegrad98]

Awesome. Um, where is the regulator? I haven't read that far along in the threads about replacing it -- is there a link around here to a diagram, etc? Not sure where my multimeter is hiding, and probably can't get to it until tomorrow anyway. But it's gonna be a sweaty commute! Thanks for the tips, MattL -- incidentally, any other ideas from the info above, now that the problem is no longer intermittent?!

Cheers, John

[Matt L]

Nothing other than to check for voltage on the input leads. They're the small ones.

The regulator is bolted to the blower mounting plate. You get there by removing the trim cover above the passenger footwell (two screws) then removing the blower cover (six or so screws). Then the blower and regulator are staring you in the face, provided you are lying on your back in the footwell.

[dukegrad98]

When the car is set to 72 on both sides and AUTO fan, the #10 voltage readout varies between 3.8 - 4.1 volts. On MAX manual fan, it reads out 6.0 volts. In either case, the blower is doing nothing -- zip, nada.

I'll find the multimeter and try to get under there sometime tomorrow. Will I find obvious contact points, or do I have to slice into the leads to get a reading? Forgive my ignorance -- never seen this regulator before, and I'm flying blind until I get in there. Just trying to be prepared, like the good boy scout, etc., etc.

I'm really not excited about the upcoming commute! Thanks again for all the help, you guys -- much appreciated.

Cheers, John

[nhdoc]

Since your blower is not working I'd check the regulator output voltage to the blower which will tell you if it is the motor or something upstream of it that is bad. Usually the regulators do not fail in such a way as to leave the blower completely inoperable so I am suspecting it is the blower itself that is bad.

Your choices then are to find a used blower and replace it and use the old regulator or go for the new, updated blower, mounting plate and regulator (assuming yours has the old style regulator) which will set you back about $800 in parts as I recall.

In other words, you cannot put the new style blower in if you still have the old style regulator...you'd need to change both parts and the old style blower is no longer sold new. If it was me I'd probably start looking for a used one. The parts recyclers on ebay sell them from time to time.

[TMAllison]

Next time you shut the car down, manually turn the CCU off using the blower speed button. When mine is in its intermitent failure mode it works correctly about 50% of the time after restarting. Sometimes the blower comes back on 30 minutes into my commute too. Never fails to come back on, is just a question of when sometimes.

Option #3 to what Marty said would be retrofiting your (E) regulator using one from a W140 that is available separately. I beleive there is a write up in the DIY section concerning that.

[dukegrad98]

Manually turning off the CCU and restarting the car has not yet been successful. My commutes are mercifully short given the heat today (about 96 degrees out), so I'm not in the car for more than 10-15 minutes at a time, but there's not even a hint of air coming from the fan.

I found a multimeter and am about to go dig into the car a bit and see if I can figure out what to measure.

Otherwise, what's the consensus on whether this is just the regulator or the whole unit? I'd like not to spend any more money than necessary, and I feel like I'm getting both answers. Maybe voltage readings will help -- I'll post back if I get something this afternoon/evening.

Thanks -- yet again.

Cheers, John

[dukegrad98]

OK, multimeter indicated about 4.8v on what I figure was the signal wire, and 13v or so on the larger (power?) wires. I saw the fan try to cut on once or twice, but it never got up more than a couple of rpm.

I've purchased the W140 regulator for about $250 at the local dealer. Part number is A1408218451. Apparently I'm going to have to cut and splice a few wires to get this working. Guess I've got a project for tonight.

Cheers, John

[Matt L]

First, apply power to the fan by grounding the big lead going between the fan and the regulator. The fan should run at full speed.