Twin blower removal and inspection (AC)

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white exec
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My Cars: 1992 BX19D Millesime
- LHD, NA, AC, RP_5800
1996 XM 2.5TD Exclusive
x 61

Twin blower removal and inspection (AC)

Post by white exec »

As part of investigating erratic blower power on our 19D (with AC), where blower speed could periodically fall away (to less than half normal), decided to check a few things out — having already fitted an additional good Gnd connection to pin 3 on the control panel connector, and checked that both blowers were actually running.

Car is '92, and now with 180,000km on the clock, so wondered about the condition of the two blower units and their motors, and the transistorised control.
.
Haynes diagram, with additional fixing points arrowed
Haynes diagram, with additional fixing points arrowed
.
Removal of the blowers
As per earlier posts, followed the advice there, but found a bit more dismantling was needed to get the blowers out:
- remove windscreen wiper arm
- remove air intake grille/panel (two plastic fasteners and the large plastic nut around the wiper stalk)
- lift out the central rain shield (the rubber seal secures its forward end)

RH "upper" (on the left as you stand in front of the car) fan needs to come out first. Unscrewed and unplugged the unit, but really struggled to lift it out without needing to lever the fresh/recirc unit backwards, to allow it out. The LH "lower" blower proved impossible to lift out like this, so found that it made sense to
- remove both screen washer reservoirs
- slacken the 10mm nuts holding the fresh/recirc units, to allow wiggle room, or better (for the LH one) removal. This LH one is designed to be more easily lifted out (it has a slotted mounting hole).

- the RH blower unit should be removed first, as it sits on top of the LH one's flange
- unbolt the bulkhead relay bracket, and move it to one side (no need to disconnect)
- remove the LH blower unit as well.

Inspecting the blowers

Motors
On the car here, both blowers were the originals (moulding dates on the casing) but were of different makes:
RH (upper) unit was SOFICO, France
LH (lower) unit was VALEO
The motors inside were essentially identical.

Removal of the motor from the casing:
SOFICO - remove the two small screws on the casing, and push the two 5mm location spigots (near the screws) firmly down to push the motor out of the casing;
VALEO - unplug the supply lead, and its 'adaptor' from the motor side. Under the adaptor you'll see (between the connectors) a black plastic tongue. Push in and gently lever this (and the motor) downwards and out of the case.

Removal of the impeller from the motor shaft:
Don't attempt this, is my recommendation. Even with the very tight and spiked circlip removed, the impeller remained tight on the shaft, and there seemed scope for damage/breakage, so it was left in position. That scuppers the oiling of one of the motor bearings, unfortunately. Did toy with the idea of drilling the impeller close to the bearing (to provide an oil hole), but didn't go down that route, which I probably should have done*. Shaft protrusion beyond the impeller was 11mm, shaft-end to impeller plastic.
(* I may well revisit this bearing lubrication, if/when the blowers next come out. A small hole (or pair, to avoid upsetting the balance) could likely be made in the impeller, so oil could be dripped into the hidden bearing.)

Inspection:
Lots of black brush dust, which was blown out with an airline.
Brushes are easily lifted out (clip, with spring underneath). 10-11mm length still there on all the brushes here.
Commutators looked good too - around 0.4mm of wear.
Rear sleeve bearing looked dry, but not at all stiff, and rotor had no noticeable end-float.
Brush holders cleaned up, and rear bearing oiled with 5W30.
All-in-all, I'd say the motors looked well-built, and in remarkable condition for 29 years' use. :)

Electrical load and transistorised control module

With the blowers on the bench, fed direct from a 12v battery, each drew 15A. This could be a bit higher on the car, of course.

Note: The motors are reversible, but the direction of rotation is clearly marked on the impeller, and perhaps not what you'd expect by looking at the blade shape. In one direction (the correct one) the blowers are extremely powerful and pull the 15A above. Reversed, doing less work, load falls to 10A.
Did notice that while the VALEO fan had its red+black cables correctly used, the SOFICO fan had them inexplicably reversed, with Black needing to be +ve. #-o

Which brings us on to the transistor control module...
Was surprised to find the one here (fitted into the lower fan intake duct) was new and shiny, marked SIEM and dated 8/01 (so 2001), so obviously a replacement.
Mounted on a very chunky aluminium (!) heat-sink was an FW26025A1 Darlington (from ST). This is rated at 20A max, so not really up to the job of 2 x 15A+ blowers, if it ever had to handle that. Aim will be to replace it with an MJ11015G (from ON) if it fails. These are rated at 30A.
Looks like the single blower modules were also used on the twin-fan models, as previously discussed.

AC expansion matrix - choked with grot! :-s
Having seen Dragon Man's alarming photo earlier (viewtopic.php?p=263587#p263587), I peered down into the now open intake/expansion matrix void of the heater unit, to find that the finned expansion matrix was around 50% blocked with sooty black fluff! Vacc'd some of this out, and washed the rest off with a bottle brush and some bio warm soapy water. Left it all nice and clean, and a decidely better air-flow through the system, and effective AC.

Re-assembly
Reverse of stripping out, with each connector given a dose of contact cleaner. Fresh/recirc flap shafts and teeth given an oiling.
Last to go back in are the washer reservoirs, then the intake grille and wiper.
Forgot the wiper motor weather shield, which I found while clearing up. There's always one.

Hope useful.

Conclusion?
Wondering whether the occasional marked falling away of blower speed could be the Darlington going into partial thermal shutdown.
This only happened on very hot days (30°+) outside, and AC and fans being used in earnest, and for some time.
The fault could be swatted by switching the AC off for 5 mins or so. Switched back on, the blower speed reverted to normal.
A largely blocked evaporator couldn't have been helping, and neither might the hefty dose of carbon dust inside each of the motors.
Chris

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David
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Re: Twin blower removal and inspection (AC)

Post by David »

white exec wrote:
Sun Sep 19, 2021 12:17 pm

Note: The motors are reversible, but the direction of rotation is clearly marked on the impeller, and perhaps not what you'd expect by looking at the blade shape. In one direction (the correct one) the blowers are extremely powerful and pull the 15A above. Reversed, doing less work, load falls to 10A.
Did notice that while the VALEO fan had its red+black cables correctly used, the SOFICO fan had them inexplicably reversed, with Black needing to be +ve.
I noticed the same thing about the black wire being +ve on one when I dismantled mine a few months ago, although I just assumed that I’d wired it up wrong in the first place. It's good to know that I wasn't imagining it!

If you look closely at the fan blades, one is marked 'D', & the other is marked 'G' (D being right & G being left in French). It's worthwhile bearing in mind if you manage to mix the fans up. The motors are both identical, and so are the fan blades themselves, except the fins on the fan blades point in opposite directions.
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

1992 Citroën BX 1.9 TXD (with GTI engine; Mulleys old car) - Parts car.

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white exec
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1996 XM 2.5TD Exclusive
x 61

Re: Twin blower removal and inspection (AC)

Post by white exec »

I didn't notice that D and G marking, but gave up on removing the impellers from their shafts anyway.
And, again not clocked at the time, the two units rotate in opposite (mirror) directions to each other.
Wonder whether the 'wrong' wiring on one of the units is down to that motor also being able to be used (ex-factory) on the other side, or as a single blower on those models? The wiring colours were wrong, but the rotation was correct, and the keyed connectors only allow one sort of connection.
Chris

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Jaba
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Re: Twin blower removal and inspection (AC)

Post by Jaba »

Its frankly amazing that after over 30 years of BX we are still increasing our knowledge as we learn, by simple observation, evermore about our voitures.
The Joy of BX with just one Citroën BX to my name now. Will I sing Bye Bye to my GTI or will it be Till death us do part.

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Re: Twin blower removal and inspection (AC)

Post by Vanny »

I actually made a video on just this topic!

Well the wiper motor change, but the first step is getting the additional blower motor out.



The haynes manual image looks wrong compared to my Mk 2, wonder if its the Mk1 system.

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white exec
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Posts: 602
Joined: Sat Sep 12, 2020 4:04 pm
Location: Sayalonga, Malaga
My Cars: 1992 BX19D Millesime
- LHD, NA, AC, RP_5800
1996 XM 2.5TD Exclusive
x 61

Re: Twin blower removal and inspection (AC)

Post by white exec »

Great video, Vanny.
Agree about the Haynes drawing, where the recirc/fresh air diverters do not look like the mk.2 items, although the blowers themselves do correspond.
Chris