no heater fan

[clickclick]

having just puchased my first volvo 460 1993 iwould be most grateful if you could tell me of anything to check apart from the fuse as to why the heater blower is not working , and possibly how easy it is to replace.thanks in advance

[CTCNetwork]

Hi,

Is it a case of no air being blown at all?
In which case the fam may well be dead - or the fan bearing.
Should be under the dash within the pipework somewhere..

Or do you get air blown - but all cold?
Heater matrix faulty perhaps?

Des. . .

[bob13]

The fan is located under the bonnet on the passenger side by the windscreen under a plastic cover. If the fan is working but only on full then the speed controling resistors have blown

[clickclick]

many thaks for your reply.wondered if there were any resistors involved as there is no at fan all presume a replacement is neededn

[Hobblygoblin]

Hi,

Have you checked that the wires are connected to the back of the control switch and that the switch works?

Just a thought...

[Ambiesda]

"having just puchased my first volvo 460 1993 iwould be most grateful if you could tell me of anything to check apart from the fuse as to why the heater blower is not working , and possibly how easy it is to replace.thanks in advance"

If it is anything like my 1990 440, then the fan unit is behind the glove compartment at the passenger side of the car. (Inside, that is)
I had to replace my one.
Remove the glove box. (A couple of screws plus light cable, unclip the spade end connectors)
Pull down the carpet slightly, (in the passenger side foot well).
If I can remember sizes correctly, undo the 4 or 5 m8 or m10 set screws.
Unplug the wiring.
The fan housing comes out totally seperate from the pipework. (No need to touch the pipework at all)
The speed controller (resistor) is also visible.
Very easy to do and replace. (Used a newer one from a local scrappie, worked perfectly)

Regards

Malky

[clickclick]

Originally Posted by clickclick

having just puchased my first volvo 460 1993 iwould be most grateful if you could tell me of anything to check apart from the fuse as to why the heater blower is not working , and possibly how easy it is to replace.thanks in advance

have now confirmed fan works switch is working so is there a relay in the circuit hiden some where.,between fuse and switch.thanks to all helpers

[clickclick]

after a bit of detective work have isolated the cause.the a.c. heating module is not swiching power to the fan so intend to bypass it.hope this might help anybody else who might have similar problem.

[bob13]

A.c. prob, that would have put a toltally different slant on solving the problem. I think the legs on the relay you need to by pass are 75 to 88b but check first. Hope this helps.

[viggy]

I had the same problem and I fixed it yesterday. Here is what happened:

I bought my 460 (1993) with the heating broken. 1st problem was the clogged heating radiator so I had it replaced. I had problems with the cabin fan too and it was driving me mad so I had the control unit replaced too (the button versions). After a year it failed. Intermittent failure led me to think it was a bad contact, a bad wire or both. Finnaly it stopped working altogather and that really ****ed me off.

I started diagnosing the problem and I noticed that if I press the ACmax button the fan magically springs to life. After looking for a schematic I found that this button activates a rellay that bypasses the fan switch. I removed part of the dash board, but before that I checked if there is some power going to the switch when I press ACmax (it abviously did) and what happens if I press the VENT button. No voltage got to the fan. I found a safe way to get 12V and delivered power to the switch and the fan worked as intended. Speeds, turn off and all. So the fan was ok, the resistor network wich governs the speed of the fan was ok, only problem was there was no power delivered to the fan except for the ACmax setting.

I took out the control module and dissasembled it. Inside there is a diode array, 3 relays and an integrated circuit (yes, a chip) marked as ULN2004A. I found the datasheet and it is a 7 transistor (a transistor is silicon [silicon as metal] based electric switch) power switch. I hoped it is ok and it turned out it was. The contol unit has two sets of connectors. Small pin and large fast-on pins. The faston pin are the ones used for power delivery and have the hefty wires running to it (and to the fan and to the resistor array). I traced the small pins and found which ones deliver power to the circuit board (small pins viewed from behind: leftmost is GROUND, the third from the right is +12V).

I powered the circuit and found that the relay intended to switch over are operating correctly, so from here on it was a power delivery problem. I measured and the voltage never appeared on the big fast-on pins as the relay correctly switched on.

Now you should know, that the relay carry a lot of current and are made of copper, which is a good conductor. Side effect is that they are heavy and vibrating them in a car (engine vibrations, going over bumps) excerts a certain force at the pcb. A pcb is short for printed circuit board, vhich is a nice way to wire up a thing. It is composed as a sandwich. Base is called raisin and is usually brown and it stinks of electronics and on top of that there is a thin foil (about 150 micrometers, remember copper is a good conductor) which is segmented into flat "wires and are usually covered with green lacquer acting as an insulator. This copper wires are actually glued quite firmly to the resin and the force, the temperature effects (stretching and contracting the materials) can cause them to break. Now this is a very subtle mechanical fault which one is able to spot only if one already saw it before. Where the relay contact landed into the pcb the copper foil broke and interrupted current flow making it impossible to reach the fast-on pin and thus failing to deliver power to the ventilator. I bridged the failed copper wire with a suitable thick little wire and the unit is now fully functional.



A very lenghty post, I know, but it is imperative to understand the mechanism to trace such an error, which is very common in units containing power (and thus heavy components). A similar error, called cold weld is very common in low power electronics, but thats another story.

I have several volvo repair manuals in german, but they are rather big to upload. Found via P2P.