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Paul T. Schram (Paulschram)
| | Posted on Friday, January 31, 2003 - 08:54 am: | 
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SWMBO went ballistic again last night at the news that the blower motor switch died-again. When I told her it was the second one and the entire assembly cost $135... It didn't get any better, in spite of my tracing the circuit on the dead one to figure out how to make a replacement.
I went to the local Advance auto parts and went through their looky book with pictures of parts, looking for one that looked like it might fit-no dice.
The circuit is pretty simple electrically, but slightly complicated mechanically, especially in a world where every electrical/electronic part on a car is purpose built (no, I'm not bashing my day job employer, but the OEM customers we have).
I figure I have a few options.
1: fixed single speed fan, always on-easiest fix, most Ghetto-tastic.
2: Three speed fan control with off-least intensive method to have some control.
3: Rotary switch mounted in the coin tray-most Ghetto-licious? I could have all four speeds and off with this method.
Any input? Has anybody found a domestic switch that will work acceptably? I don't want to buy a switch, find it won't even come close and not be able to return it.
BTW-I have a '96 coming into the shop next week for the exact same problem-but, he's willing to pay the $ for the correct part. I'll be really good at disassembling Disco dashes by the end of next week!
Peace,
Paul |
Bill Bettridge (Billb)
| | Posted on Monday, February 03, 2003 - 10:59 am: |
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Paul,
Have you considered using a RRC type slide switch and also the external resistor that comes with it? The switch seems much better built than the Disco version and the external resistor is pretty durable - though exposed to the weather in the RRC position does expire after 100K(sometimes), but that could be solved by better postioning.
Bill |
Brendan Kearns (Howboucha)
| | Posted on Monday, February 03, 2003 - 12:55 pm: |
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My slide switch is bad on my 95. I "tested" it by inserting a small screwdriver through the slot and pressing on the metal part that the switch slides against. Sure enough, the fan would blow at the setting where I depressed the screwdriver.
I tried to remove the control from the dash, but I couldn't get it to come out. I figured that the metal contact point is grimy and preventing good contact from the control lever. |
Paul T. Schram (Paulschram)
| | Posted on Monday, February 03, 2003 - 02:34 pm: |
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Brendan:
There is quite a bit more to it than just corrosion. The common connection is not robust enough to dissipate the heat generated and as a result, it buckles to the extent that the other contacts cannot make a connection. In order to remove the fan switch, you must remove the entire fascia panel, and then, you still have to remove the entire heater control panel and try to pry the switch free. Even if you do replace the entire assembly, you have only bought 50K miles or so until it dies again.
Bill:
I'm afriad that there isn't a nickel's worth of difference between the two, also, the resistor is hidden in the bowels of the disco so it isn't that easy to do.
I'm embarrassed to say that I took the ghetto route out of this one and wired a spdt switch and the fan always runs at low with a switch to go to high. It will work until I figure out a better solution. From the amount of current that is being drawn, I'm leaning towards a rotary switch and a relay assembly so the high current is drawn through the relay, rather than the switch itself.
PEace,
Paul |
Bill Bettridge (Billb)
| | Posted on Monday, February 03, 2003 - 03:05 pm: |
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Paul,
Seems there must be some difference because the RRC switches don't seem to have the failure rate that the Disco version does - if the resistor is behind the dash somewhere in the Disco and directly behind the cowling vent on the RRC - could it be related to that? (ie: the RRC resistor is always getting cooled by air coming in through the hood vent, while the Disco version burns up due to inadequate heat dispersion)??
Just something to ponder - FYI - I've never had the Disco one out (no problems so far), but have on the RRC.....so take all this with a grain of salt.
Bill |
Paul T. Schram (Paulschram)
| | Posted on Monday, February 03, 2003 - 03:31 pm: |
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Bill:
From my observations, the common connection gets cooked pretty good, as does the highest speed position. To the extent that the mating connector to the switch has begun to crack from the heat generated right at the switch, so I don't know what to expect if I were to get into the actual resistor pack.
When I bought the truck, I was well aware of the potential issues after having worked on a number of MGs... As a result, from the outset, I decided if something died, I would replace it with somthing much more robust, hence my intentions to move toward something other than OEM Rover, such as a rotary switch and relay arrangement. Fortunately, I have little use for the coin tray and it is strategically located near ground zero so to speak! The worst thing is that the switch is made by Siemens-I'd expect better from the folks who make the control mechanisms for many of our nuclear power plants!
Paul |
Bill Bettridge (Billb)
| | Posted on Monday, February 03, 2003 - 04:40 pm: |
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Interesting - RRC have diferent problem that leaves you with only highest blower setting (III) because the resistor eventually gets corroded from continuous exposure to the elements.
Glad you found a way around the OEM part - I'm not trying to belabor the point, it's just interesting.
My electrical theory is admittedly pretty crappy, but could (??) the common connection cooking be related to the resistor not getting cooled enough, or are they two completly seperate issues?
Thanks,
Bill |
Rich Lee
| | Posted on Monday, February 03, 2003 - 05:46 pm: |
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Guys,
They both suck. The RRC switch goes to 2 seperate resistors (plus no resistance) and also controls the A/C circuit on a seperate slider. One reason why it goes out is corrosion at the contacts in the the switch multi-plug. It is much easier to replace than the D1 switch, and less expensive. I have replaced it twice in the last 80k miles, the last time, I replaced the multiplug with individual spade connectors on each wire. We'll see how long that lasts.
The D1 switch is not so easy. I believe it controls seperate relays in each position (I'll have to review my ETM to confirm this) Anyway, trying to clean and de-warp the contacts only buys you a little time. I welcome anyone with info on a good 4 position rotary switch (with 1 pole constantly on) to post it here, as I don't think there is a better switch that can be dropped into the OEM position. A good quick fix is a robust DPDT switch mounted elsewhere in the dash. That will at lest give you 2 fan speeds.
Good Luck. |
Paul T. Schram (Paulschram)
| | Posted on Tuesday, February 04, 2003 - 08:48 am: |
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Rich:
The Disco uses a single relay which is grounded for the lowest speed and then uses the resistor pack, plus the relay for the additional speeds.
I was considering a rotary switch with two wafers, one for the relay which must be on in all speed positions and separate from the others. The main problem is finding a rotary switch where all contacts are capable of handling up to 25 amps of current, hence my rotary switch with separate relays to handle the higher current, rather than the rotary switch. The problem with a toggle switch is that it is difficult to have two speeds with an off position, again because of that pesky relay. The best case there would be two speeds, one of them being the lowest setting and the other one of the other speeds. Currently, I have low and high. I suppose I could wire a center-off switch and have no fan (How often do you need NO fan?), and then two speeds, either lowest and another, or two others of one's choosing.
ARGH! Now that you've gotten me thinking, I have to tear that damned dash apart again!.
Peace,
Paul |
Rich Lee
| | Posted on Tuesday, February 04, 2003 - 10:05 pm: |
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Hi Paul,
"I feel your pain"
My previously-repaired D1 blower switch now only works on the 2 lower settings, and sometimes the 3rd if I jiggle it a lot. To give me the option of max fan speed, I replaced the rear A/C blank (since I have no rear A/C) with a rectangular rocker switch commonly found at many parts stores.
This switch is wired to the highest blower speed circuit. So when the slider is in any position but off, I simply push this switch and I have max fan speed.
I cut the 2 mounting ears off the switch and filed their bases smooth. I then wrapped the switch with a couple layers of black electrical tape and it fits pretty flush within the rear A/C switch hole. It "almost" looks like it belongs there. The problem is that none of these switches (I tried 3 so far) are truly rated for the full fan load and have melted down.
My current "neanderthal" fix is the wires coming out of the same hole and commected to a big on-off rotary switch that came with my Hella 4000 wiring kit. This has not melted.
I'm willing to bet that a lot of the premature demise with the fan switch could be prevented by substituting their direct wiring to the resistors with a bank of 4 relays,one for each speed. A business opportunity for anyone who wants it.
I know this is the case for the light switch on D1s and D2s and STRONGLY suggest that anyone with over 70k miles on their Disco convert to one of the high-power relay setups for their headlights (a la Jcobs or painless wiring), regardless of the bulbs they run. |
Ali
| | Posted on Wednesday, February 05, 2003 - 01:31 pm: |
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Guys,
This is gonna sound stupid but is it possible to use a rotary switch out of another car? Perhaps a japanese model? |
Ken Tipton (Irish_Nv)
| | Posted on Wednesday, February 05, 2003 - 01:55 pm: |
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can you just hook up a relay to a switch that when turned on feeds 12v from the bat. the hot wire that comes out of the relay then goes to a variable resitor with a dial or rotary control then to the blower. Am I missing something here or can you not find one (variable resitor switch) that would handle the load of the blower at full draw. |
Paul T. Schram (Paulschram)
| | Posted on Thursday, February 06, 2003 - 08:15 am: |
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NO! The switch for the blower completes the ground side of the circuit. Hooking 12vdc to it would have unfortunate results. Also, the switch is independent of the speed selection resistor. The switch merely switches the resistors into or out of the circuit.
The problem of using the switch from another vehicle is the two circuits needed for the Disco, one just to run the relay independently of the others, and another to run speeds two through four. I believe the switch design that tries to do this with a single switch and big hunking pieces of copper or brass is why these switches fail like they do.
If I only knew how to post PDF pics to the board, this would be so much easier!
Peace,
Paul |
Brendan Kearns (Howboucha)
| | Posted on Thursday, February 06, 2003 - 05:09 pm: |
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I just tickle my switch a little on the high setting and it works now. I hate it though when it acts up, I can hear that relay just screaming, getting ready for a painfull death.
Brendan |
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