Another Bad Blower Regulator? [Solved: Bad Ignition Switch]

[dionphaneuf]

@gsxr - the fan worked on high on the PBU consistently, but low and auto only worked when I first pressed them. After, I switched to Hi, and when I went back to lo/auto they didn't work. After doing this a few times Hi also stopped working. The fact that the fan works at all makes me think switch and not regulator as I'd expect a regulator failure to just be binary alive/dead. Intermittency seemed more likely to be PBU (fine seemingly) or switch.
@luckymike do you mean just grabbing +12V from some other circuit in the underhood and connecting it to that fuse to replicate the signal that ought to be coming from the ignition?

 

[luckymike]

@gsxr - the fan worked on high on the PBU consistently, but low and auto only worked when I first pressed them. After, I switched to Hi, and when I went back to lo/auto they didn't work. After doing this a few times Hi also stopped working. The fact that the fan works at all makes me think switch and not regulator as I'd expect a regulator failure to just be binary alive/dead. Intermittency seemed more likely to be PBU (fine seemingly) or switch.@dion
@luckymike do you mean just grabbing +12V from some other circuit in the underhood and connecting it to that fuse to replicate the signal that ought to be coming from the ignition?

@dionphaneuf Exactly. I grabbed mine from a terminal behind the CAN box.

 

[nocfn]

 

[emerydc8]

mm best

@dionphaneuf try running a 12-volt jumper to the 30-amp fuse. If that fixes the problem, I THINK it means your ignition switch is bad.

In my case, I still had 12v downstream of the 30A strip fuse, so I tapped off that and connected it directly to the black red lead of the regulator (arrows). The three-prong connector comes apart and you leave the other two wires connected normally at the plug behind the brake booster. If that solves your problem, then I agree with @luckymike --It's likely a bad ignition switch and not a bad regulator. I think the 30A strip fuse is for the two radiator cooling fans, so my concern about leaving it like that was that it could overload the circuit on a hot day with the blower on high and the radiator cooling fans on high. Plus it was just a matter of time before other things would be adversely affected by the bad ignition switch.

 

[gsxr]

... I think the 30A strip fuse is for the two radiator cooling fans, so my concern about leaving it like that was that it could overload the circuit on a hot day with the blower on high and the radiator cooling fans on high. Plus it was just a matter of time before other things would be adversely affected by the bad ignition switch.

This is correct. For 1992-93 models, the extra 30A strip fuse behind the brake booster is for the 2 electric radiator/condenser cooling fans.

 

[dionphaneuf]

@emerydc8 thanks - I confirmed I had +12V at the fuse last night so @luckymike 's suggestion didn't seem to change anything. When driving the car the fan randomly turned on at one point (right after I turned on the wipers?). I moved it to auto and then low which worked, and then it randomly died. I'll try your trick of dissassembling the connector tonight but I think I want to give +12V from that 30A fuse to the Red wire on the wires to the regulator and leave the ground/black and yellow signal wire connected to the firewall and untouched. That was suggested in the post here and others adjactent to it.

 

[emerydc8]

Come to think of it, it may be the red wire to the regulator that needs 12v if the black is ground. I would have to go back and look at my pictures. In any case, if you take 12v off the top of the 30A strip fuse you can power the blower directly and bypass the pin that is supposed to be putting out 12v (and current) but is not due to a bad ignition switch.

EDIT: @dionphaneuf , it was the red wire that needs 12v. I went back and found another string on this. Blower Motor | Heating and Cooling

 

[luckymike]

Just going to throw this out there, too. Next time your blower stops, try moving the ignition key back and forth slightly. In fact, you could try it now to see if that kills the fan.

 

[dionphaneuf]

Bit of a belated update here...
I replaced the ignition switch without any success in improving the blower issue, so unless I got a defective switch it's back to blower or regulator. Is there a good way to know which one? I'm planning on pulling the car apart this weekend to do this as I bought both off of RM (ACM for regulator, Behr for Blower), would be nice to save some $$$ and return the one that isn't required. Presumably the blower would be obivously seized or brushes. That said, given that the car has 250k mi and I have no record of either being replaced, perhaps it's worth doing both anyway?

I'll also be replacing all of my plug wires (vs just the one with the torn boot) and cleaning out my EGR passage including removing the throttle body to see if I have a carbon clog on the back side as @gsxr did and clear that pesky CEL once and for all.

 

[gsxr]

A bad regulator typically results in a fixed speed, OR a limited speed range between low and "medium". And, this is not intermittent... it doesn't sometimes work on high speed.

A failing blower motor (worn brushes) can sometimes cause the fan to shut off (zero speed) and this is intermittent; but the full speed range should be available when the motor does work.

IIRC, Jono says that an old blower can kill a new regulator, and that his shop would typically replace both at the same time to avoid cranky customers returning for the same issue. (I forget if a new blower can kill an old regulator, but it seems plausible.) Since you have no record of either being replaced, I'd probably change both at the same time since you already have the parts, unless you find something else interesting when you remove the old components. If the blower has 250k and is original, it's overdue. BTW, is the new Behr blower the one made in USA/Canada instead of Grrrmany?

 

[dionphaneuf]

New Behr Blower is indeed from my home and native land.

So I pulled the car apart today without much luck. Sadly, I bought the facelift blower and will need to return and get the proper PN. But I can't seem to get either blower to work with either resistor.

• I connected my existing blower to a 12V jump pack to get +12V to it (need a power supply...) and it spins, remarkably quietly I might add
• I tried grabbing +12V from a red wire behind the can Box and running it to the 30A fuse on the brake booster (not the exterior fan fuse on the shock tower), connecting my aligator wire directly onto the middle of the 30A fuse, and no difference.
• I checked the voltage coming off the three pins of the connector that go to the fan controller. With the key in the on position, between the inboard pin (yellow wire on resistor connector/harness) and the outboard pin (black wire on resistor connector/harness) I get 1.2/4.8.7.5 on Lo/Auto/Hi respectively. But I read no voltage between the middle (red) and the outboard wires. I believe this suggests that this connector still isn't getting +12V....why would this be?

 

[Jlaa]

New Behr Blower is indeed from my home and native land.

So I pulled the car apart today without much luck. Sadly, I bought the facelift blower and will need to return and get the proper PN. But I can't seem to get either blower to work with either resistor.

• I connected my existing blower to a 12V jump pack to get +12V to it (need a power supply...) and it spins, remarkably quietly I might add
• I tried grabbing +12V from a red wire behind the can Box and running it to the 30A fuse on the brake booster (not the exterior fan fuse on the shock tower), connecting my aligator wire directly onto the middle of the 30A fuse, and no difference.
• I checked the voltage coming off the three pins of the connector that go to the fan controller. With the key in the on position, between the inboard pin (yellow wire on resistor connector/harness) and the outboard pin (black wire on resistor connector/harness) I get 1.2/4.8.7.5 on Lo/Auto/Hi respectively. But I read no voltage between the middle (red) and the outboard wires. I believe this suggests that this connector still isn't getting +12V....why would this be?

If red wire is not getting voltage, then see these two diagrams. The red wire leads back to the 30 amp fuse, then to a PK/GN wire which goes to 15X on the ignition switch.

- Are you getting 0 voltage AFTER the 30 amp fuse (F15)? If yes, then
- Are you getting 0 voltage BEFORE the 30 amp fuse (F15)? If yes then check the PK/GN wire and/or check contact 15X in the ignition switch.

 

[dionphaneuf]

From the Diagram you posted, which of Point A and Point B in my image below is Pk/Gn and which is Bk/Gn? I tried to carefully remove some of the weather stripping black insulation that covers the wires and both are red below, not the colors in the schematic.


I also tried measuring continuity and voltage among some of the different pairs of wires with mixed results. I'm getting +12V between point A and Pin 2 which seems wrong, as does the continuity between Pin 2 and ground. I'm quite confused by the continuity between point A and all the wires though.

 

[emerydc8]

Not to beat a dead horse, but I had two cars that were not producing good power to the red wire on the three-prong regulator terminal (X64?).

One car had NO voltage. Another showed 12 volts on the multi-meter but it was not enough CURRENT to drive the fan even if sent directly to the motor. I went through several new regulators before discovering it wasn't the regulator or the fan. Bad ignition switches were the reason for lack of power to the red (and yellow?) wires of the regulator. There are no guarantees that your switch is bad but have you ruled it out?

When measuring power from X64, be careful about assuming the voltage you see on the multi-meter has enough current behind it. A bad ignition switch could fool you--it fooled me.

I can't remember if this was discussed above or in another post, but another forum member pointed out that a test light may be helpful here.

I never would have thought bad ignition switches would mimic symptoms of a bad regulator or blower motor.

 

[gsxr]

• I tried grabbing +12V from a red wire behind the can Box and running it to the 30A fuse on the brake booster (not the exterior fan fuse on the shock tower), connecting my aligator wire directly onto the middle of the 30A fuse, and no difference.

I think I found part of your problem. You have the fuse locations backwards:

​

• The 30A fuse (F15) at the driver strut mount/tower is for the HVAC blower below the windshield wiper.
  
  
• The 30A fuse behind the brake booster is for the dual cooling fans behind the hood grille, ahead of the condenser. Note this applies to 1992-93 models only. And, it is *not* fuse F22/2 as shown in the ETM, this is an error in the ETM. Actually it looks like there may be errors in the aux fan schematics for multiple models, the non-V8 schematic all show no 30A fuse anywhere, just an unfused feed from X4/10. I never noticed this before. And, I don't have access to a 1990-up non-V8 car to check on this.

Check the strut tower fuse and repeat your above tests with +12v applied there.

 

[Jlaa]

I think I found part of your problem. You have the fuse locations backwards:

​

• The 30A fuse (F15) at the driver strut mount/tower is for the HVAC blower below the windshield wiper.
  
  
• The 30A fuse behind the brake booster is for the dual cooling fans behind the hood grille, ahead of the condenser. Note this applies to 1992-93 models only. And, it is *not* fuse F22/2 as shown in the ETM, this is an error in the ETM. Actually it looks like there may be errors in the aux fan schematics for multiple models, the non-V8 schematic all show no 30A fuse anywhere, just an unfused feed from X4/10. I never noticed this before. And, I don't have access to a 1990-up non-V8 car to check on this.

Check the strut tower fuse and repeat your above tests with +12v applied there.



View attachment 172934

Oh man THAT IS A GOOD CATCH!!!!! Should have seen that the fuse was the bare metal strip and thought "oh that's the electric radiator fan!"

 

[TerryA]

I think I found part of your problem. You have the fuse locations backwards:

​

• The 30A fuse (F15) at the driver strut mount/tower is for the HVAC blower below the windshield wiper.
  
  
• The 30A fuse behind the brake booster is for the dual cooling fans behind the hood grille, ahead of the condenser. Note this applies to 1992-93 models only. And, it is *not* fuse F22/2 as shown in the ETM, this is an error in the ETM. Actually it looks like there may be errors in the aux fan schematics for multiple models, the non-V8 schematic all show no 30A fuse anywhere, just an unfused feed from X4/10. I never noticed this before. And, I don't have access to a 1990-up non-V8 car to check on this.

Check the strut tower fuse and repeat your above tests with +12v applied there.



View attachment 172934

@gsxr@dionphaneuf,
I remember having blower problems with my long gone 86 300E. That aux 30 amp fuse had to be installed also because I was blowing a fuse in the fuse box.

 

[gsxr]

@gsxr@dionphaneuf,
I remember having blower problems with my long gone 86 300E. That aux 30 amp fuse had to be installed also because I was blowing a fuse in the fuse box.

Yup, the 1986-87 models originally had a standard 25A "torpedo" style HVAC blower fuse, inside the fuse box. But it got so hot, it was melting the plastic frame and would result in bad/no connection. MB released a TSB to retrofit the external 30A strip fuse instead and bypass the 25A fuse. I had to do this upgrade on my April-1986 production 1987 300D.

This was phased into standard production in mid/late 1987 model year, IIRC... all 124's from 1988-up have the 30A strip fuse for HVAC blower, located by the driver strut tower.

 

[dionphaneuf]

Thanks for all the help and pointing this out @gsxr . I checked and, sure enough, that fuse was cracked. I'm 99% sure I inspected it at the start of all of this but I missed the small crack. Replaced it and all good now. Also replaced the regulator. Still have my old blower motor in there and it's working totally fine but will likely replace it as well as a matter of course, just need to get the new one on order.

As part of this ordeal I'll have replaced my blower, regulator, underhood fuses, and ignition switch, none of which (fuse aside) had failed although I'm sure they weren't all that far off.

 

[winmutt]

Looks like I have run into the old failed ignition switch as well. While I had 12v at the firewall, I mad a "Eric O" test light with a spare H4 headlight I had lying around and sure enough, I cant get it to light up at all.

 

[emerydc8]

 

[winmutt]

Looks like I have run into the old failed ignition switch as well. While I had 12v at the firewall, I mad a "Eric O" test light with a spare H4 headlight I had lying around and sure enough, I cant get it to light up at all.

Can't tell you how frustrating in this was. 50cent fuse fell a part. At this point I have replaced regulator and ignition switch. Measured voltage and continuity 2x across this fuse. I squinted real hard at it to because I've hard it's hard to see when they are blown. Well atleast I will hopefully get it all buttoned up.and back on the road again and be a little bit wiser for it.

 

[Jlaa]

 

[gerryvz]

I always tell people before you do ANYTHING that is to do with electrical, ALWAYS check fuses first. Remove, not just cursory visual inspection.

 

[emerydc8]

Can't tell you how frustrating in this was. 50cent fuse fell a part. At this point I have replaced regulator and ignition switch.

Both parts have been known to fail as these cars age. I would look at it as preventative maintenance.

Glad you got it resolved. I think I remember posts from @gerryvz and @gsxr recommending taking that fuse out and holding it in your hand in case there is a hairline crack.

 

[winmutt]

Both parts have been known to fail as these cars age. I would look at it as preventative maintenance.

Glad you got it resolved. I think I remember posts from @gerryvz and @gsxr recommending taking that fuse out and holding it in your hand in case there is a hairline crack.

I remember the same posts and took age and eye sight into consideration with my assumptions.