Laycock overdrive volvo11/6/2022 ![]() ![]() All of the big currents are handled by thicker gauge wire for a reason. ![]() ![]() I can think of no other circuit in your car which runs 15amps with such a thin gauge wire. Fuses don't prevent equipment or harness from malfunction - they react to the malfunction. The thin wire wi'll melt long before the fuse blows and it'll take other bits of the harness with it when it does. The "problem" is that the wiring going into and back out of the gear lever knob where the overdrive switch sits is a thin spindly gauge of wire and cannot withstand 15amps persistently, which is the error condition I suggest you plan for. That means there obviously are problems which are not properly understood or addressed first time around. With the first sentence he said a relay wasn't needed and in the second sentence he said they were retrofitted when there had already been a problem. I only responded to this thread because Tony gave contradicting advice. (Relay boxes containing electronic circuits may be different, but they are generally not marketed with the basic W1,C2 etc or 87, 86 etc terminal designations.) Only those with a fitted diode across the coil windings are and the diode "points" to the more positive contact, regardless of whether you have a positive or negative earth car. Most relays are not polarity sensitive with regard to which coil winding is connected to positive or negative supply. This is a realistic possibility for these cars these days, as they are not used on a daily basis and the default position is a "closed contact" that may well never disengage. Sadly, if there is corrosion on the contacts of that armature, it may not disconnect and will permanently pull a high current. Once engaged a small armature is supposed to disconnect and leave it running with a current draw of about 2/3amp. In the case of the overdrive solenoid, it does indeed add about 16amps to the current draw to fire up the overdrive. Check my previous posts on electrical topics for details. Simply fitting a larger value fuse and incorporating that into your car's loom will provide the upstream part of the loom with little or no protection from your modifications, much like fitting a 50amp fuse for an "upgraded" fan on your radiator - the wiring will melt long before the fuse ever blows. You really DO need a relay and you also need to have a separate fuse for the overdrive solenoid additional circuit. The black box is the relay that handles the 20A peak current drawn by the O/D solenoid as well as changes the negative polarity supplied by the Volvo relay to a switched +12V. ![]() That's the one in conjunction with the oblong board with electronic bits that gives me the push button operation as well as ensures that the O/D remains disengaged when I leave 4th gear and re-engage 4th without touching the push button. My understanding: when I change out of 4th OD will automatically disengage BUT, when I change back to 4th, OD will automatically reengage, if I haven’t manually switched to the OUT position. Mine will be more basic, with 2 position IN/OUT switch. I’m guessing that the black block is a transistor that, together with the rest of the electrics, automatically disengages yr overdrive when you change out of 4th gear, as well as enabling that 1-position switch on yr knob, press it once to engage or disengage OD? Please excuse my crosspostings to three of the RWD forums but I hope to hit one that may have someone who has some information.I reckon the white thing is the relay. Does anyone have a source that I can contact or the specs on the Orings so that I can obtain them locally? This is for my son’s 88 744Ti and without the overdrive his fuel costs are really getting out of hand. I would certainly appreciate any help in locating a set of these Orings. In some earlier postings Duane thought there might be the possibility that the bar behind the pistons had worked loose and that the overdrive would eventually quit working altogether and that is exactly what has happened. I have already replaced the pressure relief spring. I do not need a complete set of Orings for the overdrive as I just went through it 20,000 miles ago. He has always been my source for Laycock overdrive parts so I have been patient hoping I would be able to reach him. I am in dire need of a set of piston Orings for a Laycock P type overdrive.ĭuane (ODGuru) has not used his login here at the Brickboard since March 18 and I have been unable to reach him via email or snail mail at his home address. ![]()
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