The definitive heater modification

[ed4ferrets]

I've seen no reference to the other type of circuit board, brand named CHAUSSON as opposed to the ELEDASA (Valeo) as pictured. Just wondering if it also has the same shortcoming as I've never heard the relay click when turning it to max? The pcb is in front of me but the circuits are not very clear, being covered by a protective white film of sorts .... hence unable provide a pic! This is off a K reg BX. Hope I haven't missed a previous posting asking the same thing

[kermit the frog]

hi
your heater mod was fantastic.
my heater controls have been up the proverbial creek for quite a while
and i had learned to work round the problem.but thanks to your guide i now have a set of fully operational and uprated heater controls .
with the circuit board mod the fan is almost as strong as the hurricane,
im glad i dont wear a hair piece as it would now be on the rear parcel shelf
thanks again GREAT MOD!!!!!

[AndersDK]

I've seen no reference to the other type of circuit board, brand named CHAUSSON as opposed to the ELEDASA (Valeo) as pictured. Just wondering if it also has the same shortcoming as I've never heard the relay click when turning it to max? The pcb is in front of me but the circuits are not very clear, being covered by a protective white film of sorts .... hence unable provide a pic! This is off a K reg BX. Hope I haven't missed a previous posting asking the same thing

The plot is if the high speed relay is cutting in or not.
If you lean down to the steering column and hear a characteristic faint relay click while turning the fan blower control up, then there is nothing to modify.

If you dont hear that relay clicking and the fan does not kick into "hurricane" mode when the control is turned fully cw, then you need to modify.

It would be wise to turn off your 400Watts bass & drums before the test

[ami8i]

Hello,
I saved this topic on Thu Mar 22, 2007 --> today I just 'flew' about the new postings and recognised that your're talking about relais (always).

It looks that my BX 16 Break TGI (model 1992) hasn't got a relais --> the modifications doesn't work. I burnt 2 control panels because the current was too high. Also the control resitor layer suffered.
Now I know what the printed resistors are for! They limit the current to protect the layer!

I scrapped another BX which has got a relais. One day (before winter) I'll try to combine the original with the luxury harness.

I put in a simple switch for 'cool' vacation trip.

Take care!
»Horst

[Kitch]

I have at last performed the heater modification. Sadly, it now rotates only around 2rpm faster than it did before, so I don't think it was all that bad to begin with! Although the relay does now click, which before it didn't.

[Boxwolf]

While taking the circuit board out to fit new bulbs, I attempted this modification. After modifying the board and testing my new connection I stuck it back in, the lights came on (as I had hoped) and twiddling with the blower control seemed to work briefly, but then nothing. I took it all apart again, checked the little spring that bridges the tracks on the dial was in place, tried shorting the tracks together with a screwdriver ... nothing.

It looks that my BX 16 Break TGI (model 1992) hasn't got a relais --> the modifications doesn't work. I burnt 2 control panels because the current was too high. Also the control resitor layer suffered.

I hope this is not the case with all '92 model BX's as mine is a 92 one. I dont know which fuse the fan is, can anyone shed some light on this?

[Boxwolf]

terminal 3 wasnt earthing I got new bulbs which worked and thus illuminated I put a screw driver across 2 & 3 and it started to blow. I rotated the white dial and It increased to full power. IT WAS A PROBLEM WITH THE EARTH. Thanks for your help.

Same with mine, I (badly) soldered track 2 and 3 together and now the blower works fine, but sadly I had to undo the modification as it wasnt working on full power setting at all, no relay tick, nothing.

[DFF53]

If my fan does not work at all in the first place will this modification help?

[electrokid]

I tried this mod today - at first it didn't work. Turning the control up from zero started the fan running but then moving it past halfway it started to slow down again.

As others have found, 'pin 3' wasn't grounded and soldering a bridge across to the ground connection of the bulb circuit made it work fine.

I hadn't read the whole thread so I found it out the hard way but one thing I did notice while trying to find out why the mod wasn't working was that the heater speed was variable when I bashed the relay (a well know engineering technique of course )

Relay contacts are usually designed to have a slight 'wiping action' and this helps to keep the contacts clean by scraping off any surface corrosion that could stop them working. I figure that before I did the mod, the relay has sat there not operating for 18 years / 200K miles and not had this cleaning action so had become intermittantly high resistance thus changing the speed of the fan at times.

Fan speed varying intermittantly could be cause by corroded contacts on this relay - the simplest remedy is to do this mod because when the relay operates the contacts will get cleaned. Bashing my relay now has no effect on fan speed - the contacts are now clean after only a few operations.

Many thanks to Doz for the details - excellent

[Wooscary]

Just had a look at doing this, in the first instance just as instructions to get in to the control knobs to clean them as I was only getting "on full blast" or nothing.

So that's sorted, and it turns out on closer inspection that mine appears to be one where the mod is not required, which is a shame, I had the iron out heating up and everything. Oh well.

[Defender110]

My heater blower stopped working in my TZD this week;
I used this thread to find the fault was as described in posts above the heater earth track no longer earthing. A simple connection from the heater Earth no.2 to no.3 the lamp earth (if counting from the right facing forward (3&4 if counting from the left)) I did a temporary permanent repair by twisting some wire strands round the base of the lugs before plugging back in.
I didn't bother with the modification as I didn't want to risk the pitfalls encountered by some of the others on my 93 car and my blower is strong enouth anyway on full.

Thanks to DOZ for the pictorial and the others for pinpointing the earth problem. This thread saved me hours of head scratching.

[Vanny]

Just before go and (finally) do this, it dawns on me that there must be a reason Citroen never did it! I'm about to modify a brand new panel which was allegedly made in Jan 1994, and isn't wired to max fans.

I begin to wonder, if the reason it was never done, was to prolong the life of the PMOS / blower motor? Now if i had the technical spec for the motor it would be easy to figure out, but i don't, sad.

So, of those who've tried this mod, has anyone seen any problems?

[mat_fenwick]

Not after 6 years, but like you I can't see why they would deliberately stop the max speed relay from operating. I rarely use full speed so is possible I'm only 'getting away with it' rather than it being 100% OK.

[electrokid]

My fan 'top speed' no longer works and I haven't been bothered to dig in and find out why yet - can't see that it's anything to do with the mod though.

it dawns on me that there must be a reason Citroën never did it!

Most likely to be the same reason they put the paint code for Furio red on the inner wing - then painted it Venetian Red

[Jayboy]

Errr, because 'Venetian Red' and 'Rouge Furio' are the same colour....