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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Radio Suppression Relay mysteryViews : 943 Replies : 26Users Viewing This Thread : |
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Jun 10th, 2019, 23:28 | #11 |
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Good point!
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Jun 11th, 2019, 03:33 | #12 |
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Radio suppression relay location
Is this relay involved in switching injectors on and off?
And in doing so, it may generates a lot of interference, so it is located some way away from the radio? If so, where is it? I'd like to have a spare, to go with my other spare relays, as I read it can be the source of troubles... ('97 940 LPT). |
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Jun 11th, 2019, 09:28 | #13 | |
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There are two possible locations, one is by the coolant expansion tank and the other is N/S inner wing near the suspension turret. It's the same sort of relay as used by the electric cooling fan. As for the source of trouble, it can be but mainly because the mechanical side of it wears and/or the coil burns out. The contacts rarely suffer as they don't switch a "live" load, they only provide power to the injectors, the actual switching on/off of the injectors is done by the ECU as a relay couldn't cope with the frequency or speed at which the injectors are on/off in use.
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Jun 11th, 2019, 13:04 | #14 |
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Super!
Thanks Dave. I'll have a look when I'm next mobile. And oddly enough, I have a spare s/h fan relay. I should swap it for the RF relay, just to know it's good...
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Jun 11th, 2019, 13:28 | #15 |
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And..
And thanks for the precision of the reply, too. I can see from other posts that you have an electronics background- a handy thing for naughty cars. I had a temp job when I left school selling VW parts. I remember people being almost in tears when they found out the cost of the electronic + mechanical flasher relays. 8 or 9 quid in the late 70's, for a little relay and a pre NE555 astable circuit. I acquired the odd 'broken' one, and gave the contacts a file, then gave these to the needy. I went on to work with 'live' sound, so me and electricity are mates! My next project is to identify and get the fuel pump relay. I see these on fleabay, but need to locate mine, and it's part number. Somewhere in the relay tray, behind the fuses...
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Jun 11th, 2019, 14:14 | #16 | |
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That said John, you've given me a nice idea, thanks! Kind of fuel relay related so i'll explain briefly. I seem to have lost the "prime" function from the ECU (which some say never existed on the LH2.x) so need to flick the starter and wait a second while the pumps run before starting, at which point it fires first touch. I bought a time delay relay on ebay that turned out to be incorrectly described (something lost in the Chinese > Chinglish > English translations!) that turned out to be unsuitable for what i needed. I should have thought of the 555 sooner and worked out what i need for it to add a 2 second prime when i either first switch the ignition on or preferably, open the door. However i have a new in-tank pump to fit first so hoping that improves matters in terms of retaining fuel pressure. I'd be tempted to not swap the RSR at the moment, disturbing the connections could do more harm than good as i'm sure you can appreciate. Also the fan relay switches a "live" load in as much as when it operates, the fan pulls current (including inrush) from the moment those contacts make. That means the contacts are more prone to arcing so you could also be introducing a trouble spot into something that currently has no trouble.
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Jun 12th, 2019, 08:38 | #17 | |
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On the 555 front, I looked up the current capability, what with it being a small chip. 200ma. I don't know if that will suit your 'tickle the carb' project? I looked around for 'hi power alternatives to ne555' and frequently saw that people stick a power mosfet on the output. And supporting components etc. And then a bit of lateral thinking gave me the name 'Vellerman kits'. Velleman Interval Timer Minikit MK111 VellemanMK1115410329001117 ex VAT £3.25 http://www.velleman.co.uk/contents/en-uk/p37_mk111.html Build it yourself or get the iron out. 3 amp relay. Is 3 amps enough though? And good luck with the in tank pump. One day I might attend to my fuel gauge sender, which is 'non linear' below 50 pc... And I very much take your points about swapping the RSR. On something else recently, I can't remember what, the phrase ' if it ain't broke' really finally came home to me. I might just flash the spare relay on the fan circuit, or even just battery it and measure the contacts. Maybe I should get off my bum, and clean up the contacts on my sunroof switch, with a spare to hand, in case I break it... Cheers. |
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Jun 12th, 2019, 10:00 | #18 | |
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Interesting thoughts about the Vellemann kit, i wasn't sure if they were still in existence with the demise of Maplins as i believe there was some sort of owneship deal between the two of them. That kit you linked to is an astable set up, i need a monostable set up and so far, the favourite set-up seems to be a blocking diode on pin 2 connected to the drivers door pillar switch for the trigger pulse. If this 760 is like the other 740s i've had, the drivers switch will be a two element animal, one for the courtesy lights in general and the other to trigger the courtesy light timer. The way it is at the moment, there's a connection from the -ve end of the coil on the fuel pump relay to the ECU, when the ECU takes this low, the fuel pump relay is energised. My idea is to interrupt this cable with a SPCO relay, when the coil of said relay is energised, it will take the fuel pump relay coil to earth while disconnecting the ECU from the relay. This will prime the pumps for 2-3 seconds or whatever the time is set at on the 555 circuit, then hand control back to the ECU by de-energising the relay. The 555 is capable of operating most relays so that shouldn't be a problem. It would have to be set up so the 555 was sourcing the relay, the big problem with the one i bought on fleabay is that it sinks the relay which would obviously draw more current almost all of the time - whether i'm in the car or not. Interesting idea about adding a numerical readout to the Volvo code reader. As i understand it, each code is 3 digits and there are no codes that have a zero in - is that correct? If so, the first digit is fairly easy - link the pulse that currently lights the LED on the code reader to the input of a BCD counter, the output of that to a 7-segment driver and a 7-segment display. The next digit is a bit more awkward and also gives you choices on how to do the rest of the display. First, you need to detect the pause, a missing pulse detector if you like. When this missing pulse is detected, you either need to rest the single 7-segment display/counter so the next pulse starts the count again or moves the pulse input to the next counter/display driver. Likewise with the next digit. Then you have another choice - if you've got a 3-digit display for the first code, does it reset after the first code and then display the second or does it move on to a second set of digits and if so, where do you stop? Do you have ten 3-digit displays? There are several ways and means of doing it, cost would probably become a limiting factor though!
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Jun 12th, 2019, 19:40 | #19 | |
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Ok. I see were you are with the '555' idea, and the surrounding circuit. Pity that the Vellermanns is astable- I knew you needed a monostable, and perhaps a relay- I wasn't reading carefully! Your pursuit of the matter is almost like my curiosity as to why my volvo needs an amount of cranking before it fires, even when hot. Not an awful amount. It's just that other cars seems to fire somewhat quicker. Starter spin speed perhaps? And the code reader. I think you may be right about no zeros. My electronics background has been mainly about the analogue stuff in between a microphone and a loudspeaker, and their power supplies, back then. I have some oversight of digital audio principles. I made the odd foray into TTL/CMOS devices, and logic, but not much. I can just grasp the BCD and seven segment thinking. And what to do with the pause! I studied Ethernet for a bit. A least a packet on a network has something to say 'this is the start' whereas here we're dealing with silence/a low, for a period of time. (the electronics concept of a 'clock' has just come back to me). I've been (slightly) curious about these things called PICs, Audinos and Raspberry PI's, as people seem to be quick to turn to them these days. As you say, there are probably several approaches, and time and cost exist. I'm hoping I meet up with one of the Gurus, when I go to get my code reader soldering done. Maybe I can PIC their brains... And. Missing pulse detector using - a 555! That 555 is such a versatile chip! https://electronicsarea.com/missing-...uit-555-timer/ PS I don't think I'll make it as king of the code readers. Regards. |
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Jun 12th, 2019, 20:55 | #20 | |
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Two possibilities here, either it's not priming or the "check valve" aka non-return valve on the pump outlet has gone weak/failed allowing the pressure in the fuel rail to leak back to tank via the pump. This will also cause fuel vapourisation on hot days/after a long hot run (worse when both happen!) so i'm hoping it's as simple as not priming. Anecdotal evidence from doing the flick the starter thing suggests it's simply not priming but could still be the check valve/NRV at fault. I did try fitting an aftermarket NRV on the tank output on mine, i have the two pump set-up so the in-tank pump is at most 19psi output but can deliver 60 gallons/hour. The underbody pump runs at up to 60psi and without checking, i can't remember the flow but it needs the in-tank pump as it's not capable of enough suction to overcome the NRV if the in-tank pump has failed. I now have a replacement in-tank pump to fit to mine and if that works, i'll refit the NRV and try it again. I've just realised we're waffling about fuel supply problems on Ellies RSR thread - sorry Ellie! <insert blushing/sorry emoji here>
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