| Author | Message | ||
     Benoit Leus Prolific User Username: benoitleus Post Number: 199 Registered: 6-2009 |
Yesterday a strange fault appeared on my '79 Shadow. With the transmission in D or R and not applying any throttle there is a loud rattling noise coming from behind the speedometer. I took out the speedometer and test drove the car again. The rattling sound was stil there and seemed to come from a relay just under the speedometer. When I touched it, it was really vibrating quite badly. Once you give it some throttle or put the transmission in P or N the rattle stops immediately. Also, this only happens after you've been driving a while and the engine and transmission are hot. I now wonder : is this a bad relay or is something else causing the relay to behave like this ? Benoit | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1288 Registered: 6-2009 |
Benoit, Does it sound anything like the nasty clattering noise in the videos I posted on the thread, Wiper Parking on Shadow II (& Intermittent Function)? That was cured by replacing the relays, and your description sounds similar. Of course, as part of that replacement I also did cleaning of the slide connectors and coating all connections with Sanchem NoOxId electrically conducuctive grease. You might want to check if any of your relay male slides or the female wire slides have corroded/oxidized and see if cleaning them up first might solve the problem. Brian | ||
| Jeff Young Prolific User Username: jeyjey Post Number: 213 Registered: 10-2010 |
I had a bouncy relay that turned out to be the hot-water sensor giving erratic readings. That relay is under the glove box, not behind the speedo, so it’s a different relay. Just saying that a bouncy relay could be a fault in the relay, or it could be a fault in whatever is feeding the relay. Cheers, Jeff. | ||
| bob uk Unregistered guest Posted From: 188.29.164.184 |
The relay is probably ok but should be changed because the frequency of operation the buzzing will damage said relay. The fault is somethong else and the buzzing is a symptom. Somehow a small current is getting to the relay coil and then fading when relay points close thus causing the buzzer effect. So check earths and lives associated with that circuit. (Message approved by david_gore) | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 200 Registered: 6-2009 |
Brian, the sound seems to be different. My relay rattles like a machine gun. Bob, as the rattling noise only occurs with engine and transmission warmed up, standing still with the transmission in D or R and no throttle at all, am I right in supposing it has to do with the speedo transducer and/or its electrical circuit to the relay ? Benoit | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 201 Registered: 6-2009 |
It turned out to be just a loose connection on one of the relays, although it took some time to find it. I didn't realize this could cause such a racket. Benoit | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1290 Registered: 6-2009 |
Benoit, Isn't it amazing the din that rapid cycling of a tiny contact can make? I often wonder if the acoustics of the relay "can" itself amplifies this, or if it is amplified by being carried through the chassis at the mount point. Brian | ||
| bob uk Unregistered guest Posted From: 188.29.165.91 |
What happened is that the loose connection allowed enough current only to energise the relay coil. When the load of what the relay runs comes on the is not enough current to energise the coil. The contacts open and then there is enough current to energise the coil and so on. He noise can vary from buzzing to machine gunning. Keep an eye on that relay because buzzing can damage the contacts leading to failure. If it works OK for say 500 miles then forget. I am pleased that I correctly id the fault. I shall award myself a medal. (Message approved by david_gore) | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 202 Registered: 6-2009 |
It was probably too easy a fix. The rattling relay is back and no amount of fiddling with the connections could silence it. Replacing the relay with a new one didn't help. From its location (under the dash, next to the overheating buzzer) I suspect it is the speed control relay, altough the colours of the different wires doesn't match with the wiring diagram in the workshop manual. The rattling is only present with all systems warmed up and the engine idling at low revs. Once you give it some throttle the rattling stops. Only when I removed a brown/yellow wire from the W2 connection the rattling stopped immediately. Problem is I do not know what the function of that wire is. The car drives perfectly well, all systems seem to work, even the speed control. Does anyone know where that wire comes from ? | ||
| Chris Browne Prolific User Username: chrisb Post Number: 199 Registered: 2-2010 |
Hi Benoit, I think the relay you are referring to is the fuel pump relay not the speed control. I had the same chattering on my '79 Shadow 2. I eventually traced the cause of the problem to a faulty oil pressure sensor on the oil filter housing. At idle, when the engine is up to temperature, the oil pressure is relatively low and if the sensor is reading low, it assumes that the oil pressure is reaching a critical level and attempts to switch off the fuel pumps to save the engine. The chattering is the relay trying to make its mind up whether or not to cut the power to the pumps. If the chattering disappears when you increase the revs slightly (and therefore the oil pressure) that is your problem. The oil pressure sensor is the small one of three on the oil filter housing at one end. You could also pull off the wire to the sensor to see if that stops the relay chattering. Replacement sensor is about £10 UK and takes five minutes to fit. Hope this helps. Kind regards, Chris | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 203 Registered: 6-2009 |
The arrow in the picture indicates the brown/yellow wire mentioned in the previous post.  | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 204 Registered: 6-2009 |
Hi Chris, your idea sounds very logical. I'll check it out and report back. Thanks, Benoit | ||
| Chris Browne Prolific User Username: chrisb Post Number: 200 Registered: 2-2010 |
Hi Benoit, The brown/yellow wire connects the relay to the oil pressure sensor switch on the oil filter housing and if you disconnect it and the chattering stops, that would indicate that it is the oil pressure sender which is at fault. The part number is UE44823. It simply screws out of the oil filter housing and if you are quick to screw in the replacement, you will lose little oil. Kind regards, Chris | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1304 Registered: 6-2009 |
Benoit, These two diagrams may prove helpful when it comes to determining what's what when it comes to wires going to any given relay. You could have pulled either W1 or W2 and that does the same thing: disables the coil in the relay. When that's out of the picture it can't keep trying to close and open the switch it controls which is what you're hearing clattering.   If you're not near to a Crewe Original parts supplier and are willing to use a substitute oil pressure switch, ones used on the SY cars were also used on myriad GM cars of the era, too. One of the regulars here found it's the same as the oil pressure switch on a 1973 Chevrolet V8. In looking at chapters K11 and A10 of the parts manual the only reference I can find to the oil pressure switch shows part number UE33647 from beginning to end of the SY series cars. This is the oil pressure safety switch, which deals with shutting the engine down, not the oil pressure transmitter which is part UD11663 for the one series and UE40480 for the two series cars (except Camargue). Brian | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 205 Registered: 6-2009 |
This gets stranger and stranger. I just checked the oil filter housing and discovered that my '79 UK-spec Shadow has three transmitters in the housing. UE40480 : oil pressure gauge sender UE44823 : oil pressure warning light (white/brown wire). And then the odd one out : UE42725 oil temperature switch. I thought this was normally only fitted to US and Japanese spec cars. A brown/yellow wire is connected to this one. Over the next few days, when I have some time to drive the car I will disconnect first one wire and then the other to see which transmitter might be faulty. | ||
| Chris Browne Prolific User Username: chrisb Post Number: 202 Registered: 2-2010 |
Hi Benoit, The set up on my '79 Shadow 2 is exactly the same. The sensor you need to isolate is the small one on the end (see photo attached). It should have a brown wire with a yellow tracer.  Kind regards, Chris | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 206 Registered: 6-2009 |
Hi Chris, the setup on your car is indeed the same as on mine. I have now disconnected the brown/yellow wire and will see if this stops the relay noise. If so, I have a new transmitter lying around that I can fit. I just wonder why our cars have that extra transmitter ? Benoit | ||
| David Gore Moderator Username: david_gore Post Number: 1612 Registered: 4-2003 |
Benoit, The reason the extra transmitter is fitted but not used would be to eliminate the need to carry two versions of the housings in both production stock and spare parts stock. The extra cost of including the additional transmitter would be much less than the future stock holding cost for the extra spare parts that would have to be carried let alone the ever-present risk that the wrong part could be dispatched especially to international customers. | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 209 Registered: 6-2009 |
Chris was right. I disconnected the brown/yellow wire from the oil pressure sensor, took it on a testdrive today and the relay stayed silent. I'll now replace it with a new one I have lying around. Thanks everyone for your help. Benoit | ||
| Chris Browne Prolific User Username: chrisb Post Number: 209 Registered: 2-2010 |
Great news, Benoit! I'm glad you found the fault. It stopped me enjoying my car when it happened to me because I lost confidence in it. I never knew when it was likely to cut out. NOT funny on a motorway! Kind regards, Chris |
