mojojo Posted February 14, 2012 Report Share Posted February 14, 2012 I'm having an intermittent problem with my IAC. Intermittantly, maybe every other time or every time, the IAC will continue to run after the car has been shut off... Not for a few minutes, but hours. This eventually drains the battery and the car can not start after sitting for ~ 1 day. I recently replaced my battery under warranty from a split cell, most likely. At this time I replaced the Negative battery terminal. About the same time as the battery was replaced, I by passed my dimmer switch to regain my dash lights. I do have another IAC that I will try, but I'm wondering if anyone else has had this problem, and what was the solution(s). Thanks. 1995 850 T5-R 401K+ Link to comment Share on other sites More sharing options...
mojojo Posted February 14, 2012 Author Report Share Posted February 14, 2012 removed and cleaned IAC motor. After, tested as follows, (resistance across terminals - don't know why, thought I read it somewhere): 1-2: 12.2 Ohms 1-3: 22.9 Ohms 2-3: 10.9 Ohms The motor can be heard and moves freely, on the bench (open->close, close->open, etc...). Help, please. Idle is smooth and consistent in all scenarios. I just found this thread, and will check the temp sensor connection. The temp sensor has never been replaced by me. http://volvoforums.com/forum/volvo-850-16/iac-valve-44004/ Link to comment Share on other sites More sharing options...
Meek Posted February 15, 2012 Report Share Posted February 15, 2012 My car just started draining the battery too... :blush: Link to comment Share on other sites More sharing options...
mojojo Posted February 15, 2012 Author Report Share Posted February 15, 2012 swapped in a spare IAC, and same results. Now that every time I check the IAC once the car is shut down, there's no way of telling whether or not the IAC will keep running (some times it does, some times it doesn't). I also tried swapping the IAC when the scenario is occurring (car shut down, IAC continues to run), and the swapped motor instantly starts running. So, for some reason this thing is continuing to get power when it should not. Is there a relay that controls the IAC, or this 'system' in the vehicle? Link to comment Share on other sites More sharing options...
BlackT5 Posted February 15, 2012 Report Share Posted February 15, 2012 Wiring for the IAC is as follows Blue/black wire: Closing signal from ECU Pin #A25 Blue/white wire: Opening signal from ECU Pin #A11 Green wire: 12V Power supply from main relay through ECU Pin #A27. The green wire from the ECU also powers the injectors and MAF. Hard to say what would cause it to keep running, try checking your MAF and injector connections. Link to comment Share on other sites More sharing options...
mojojo Posted February 16, 2012 Author Report Share Posted February 16, 2012 So, what's the common link between the MAF, IAC, and fuel injectors? Exactly as you suggested, when the IAC is hot, so are the injectors, and the MAF. I've checked all the fuses, and removed each one while the IAC was hot, and none of the fuses removed power from the IAC, same for the relays, in the central fuse block. Visually, I only found one area to be suspect, and that hunch has lead me to an almost dead give away. Checking the area of the harness that is clipped in to the radiator fan, I was able to un-clip them and give them a slight jiggle. Instantly, the IAC (and MAF, injectors) lost power. These wires go to the relays/parts underneath the oh so commonly broken radiator fan cover. There is a beige relay here, labeled 'Volvo' with some part numbers. There are, by memory, I think, two red wires, a green wire and an Or/Bk wire leading to this relay. The relay case is broken, so it merely rests under the cover. Twice I've been able to maneuver the wires and instantly lose the power to the IAC. Thinking, if this issue was due to an issue in the harness, I should be able to shake them to lose power, but also shake them to gain power. If the relay was in question, I may be able to shake it to lose a sticking contact, but no matter how much I move it, It won't open/close without the proper voltage (power). So, what is the purpose of this relay? I will inspect the relay today while I'm in the shop (at work), and determine whether it may be salvageable. As well, I know I have another of these relays floating around, that I saved a few years back, it's just a matter of locating it. So, what's this beige relay under the radiator shroud cover for? Link to comment Share on other sites More sharing options...
BlackT5 Posted February 16, 2012 Report Share Posted February 16, 2012 Do you have a pic of it or a part #? Link to comment Share on other sites More sharing options...
mojojo Posted February 17, 2012 Author Report Share Posted February 17, 2012 beige/tan in color. Only markings are: VOLVO 3 545 803 89 9983 000 12V 40A made in Hungary Location is under neath the radiator fan shroud cover, (driver side - opposite side from cooling fan relay). Link to comment Share on other sites More sharing options...
BlackT5 Posted February 17, 2012 Report Share Posted February 17, 2012 Looks like it might be a fuel system relay? http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=20879 Which would explain things since the power for the fuel injectors also feed the IAC and MAF. If you can't find your replacement relay, I probably have one I can send you for cheap. I'll have to look when I get home. Link to comment Share on other sites More sharing options...
mojojo Posted February 17, 2012 Author Report Share Posted February 17, 2012 This is the relay that is in question. I inspected the relay yesterday, and found the contacts (inside the relay) to be in less than desirable condition, but overall working order. I cleaned the relay and re installed it. After inspection, I don't think the relay is at fault, given my logic in post #7... though the problem has not occurred again. I think I will have to unwrap the harness and have a better look at it this weekend... Link to comment Share on other sites More sharing options...
mojojo Posted February 22, 2012 Author Report Share Posted February 22, 2012 02/21/2012 Problem Solved After inspecting the harness leading to the relay in question, I found only what was to be expected from 17+ year old wires. The conduit has become very dry and cracked in several places, allowing corrosion to set in. Only doing what I can to prevent any more of the elements from getting to the old copper, I de-pinned wires and used heat shrink on the areas that were bad enough. Diagnosis- Faulty Relay After inspecting the harness, I thought back to what, exactly, I did when I checked the relay (I'm a mechanic by day, so I work on a lot of different things - it's very easy to forget what was done the day before). I checked to make sure the relay was operating properly before dis assembly. The relay was working properly. Observing the contacts of the relay - the contacts that touch (source of the typical 'clicking' noise) when power is applied, I noticed a 'spike' to be forming on one end. Not sure exactly how this happened, other than over time, the points arching so many times, and staying hot, may have allowed the materials to migrate. I cleaned both sides with a fine jewel file, and reinstalled the relay. I have not had any issues since (about a week). Of course, the easy thing would have been to replace the relay, but not having one on hand left me with the only option of attempting to repair mine. Thanks for the help. Link to comment Share on other sites More sharing options...
mojojo Posted February 24, 2012 Author Report Share Posted February 24, 2012 Few days later and still no issues. Uploaded some pictures of the spare relay I finally found, which does not resemble the faulty relay's condition... Link to comment Share on other sites More sharing options...
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