ylstaffer Posted August 23, 2009 Report Share Posted August 23, 2009 So the AC on my 98 V70 is a no-show. Took it to a local shop and they evacuated the system, recharged it, discovered no issues, but the compressor would not engage. The tech tested all the relays he could think of and they all tested 'positive', so we are at an impasse. What could possibly keep the compressor from coming on? Any hints out there? Thanks. Link to comment Share on other sites More sharing options...
DHV70 Posted August 23, 2009 Report Share Posted August 23, 2009 does the compressor actually work? and if so... maybe it just needs to be shimmed? Link to comment Share on other sites More sharing options...
dick Posted August 23, 2009 Report Share Posted August 23, 2009 So the AC on my 98 V70 is a no-show. Took it to a local shop and they evacuated the system, recharged it, discovered no issues, but the compressor would not engage. The tech tested all the relays he could think of and they all tested 'positive', so we are at an impasse. What could possibly keep the compressor from coming on? Any hints out there? Thanks. Check the pressostat. They do go bad. Unplug the wire to the 'stat and use a jumper wire across the two wires in the plug. See if that works first. Link to comment Share on other sites More sharing options...
ylstaffer Posted August 23, 2009 Author Report Share Posted August 23, 2009 The tech told me that the compressor was good (not certain how he knew that). Where exactly is this 'pressostat' located? Link to comment Share on other sites More sharing options...
dick Posted August 23, 2009 Report Share Posted August 23, 2009 The tech told me that the compressor was good (not certain how he knew that). Where exactly is this 'pressostat' located? Passenger side, on top close to where AC goes into firewall. Link to comment Share on other sites More sharing options...
ylstaffer Posted August 24, 2009 Author Report Share Posted August 24, 2009 Passenger side, on top close to where AC goes into firewall. In my research I've discovered that there are 2 pressure switches for a 98 V70, one located near the firewall (on the high pressure line) and one located behind the right (pass) side headlight (on the low pressure line). I also read where people have 'jumped' these switches to engage the compressor. Is this information correct? Link to comment Share on other sites More sharing options...
ylstaffer Posted August 24, 2009 Author Report Share Posted August 24, 2009 In my research I've discovered that there are 2 pressure switches for a 98 V70, one located near the firewall (on the high pressure line) and one located behind the right (pass) side headlight (on the low pressure line). I also read where people have 'jumped' these switches to engage the compressor. Is this information correct? So I unplugged the connector for the upper switch and jumped the wires and... nothing. I did the same for the lower one, which has 3 wires, and when I jumped two of them the cooling fan came on and so did the CEL. I cleared the CEL and it hasn't returned yet. I also checked the wires for power. On the upper connector, neither wire was 'hot'. Shouldn't one of them be? On the lower connector, one of the three wires had a low voltage to it and when I jumped it to the wire next to it the fan came on. The other wire had no response. I'm assuming that when I did all this it tripped the CEL. I'm still thinking that one of the wires on the upper connector should have power to it and I'm wondering why it doesn't. Any suggestions out there? Link to comment Share on other sites More sharing options...
Gilhuly Posted August 24, 2009 Report Share Posted August 24, 2009 The a/c clutch is electromagnetic. If the clutch gap is too great, the compressor is not going to engage. Jump the connector near the firewall and give the clutch a little help. So I unplugged the connector for the upper switch and jumped the wires and... nothing. I did the same for the lower one, which has 3 wires, and when I jumped two of them the cooling fan came on and so did the CEL. I cleared the CEL and it hasn't returned yet. I also checked the wires for power. On the upper connector, neither wire was 'hot'. Shouldn't one of them be? On the lower connector, one of the three wires had a low voltage to it and when I jumped it to the wire next to it the fan came on. The other wire had no response. I'm assuming that when I did all this it tripped the CEL. I'm still thinking that one of the wires on the upper connector should have power to it and I'm wondering why it doesn't. Any suggestions out there? Link to comment Share on other sites More sharing options...
rocketman4321 Posted August 24, 2009 Report Share Posted August 24, 2009 Agree. I replaced the clutch and shimmed a 740's in place, but I doubt you can get the clutch off it that tight space on these FWD models. Link to comment Share on other sites More sharing options...
ylstaffer Posted August 25, 2009 Author Report Share Posted August 25, 2009 The a/c clutch is electromagnetic. If the clutch gap is too great, the compressor is not going to engage. Jump the connector near the firewall and give the clutch a little help. But... shouldn't one of those wires that I'm jumping be 'hot'? Neither have any voltage. Link to comment Share on other sites More sharing options...
D s50r Posted August 25, 2009 Report Share Posted August 25, 2009 if you have power at the one wire on the compressor and the clutch is not working then you have a bad compressor Link to comment Share on other sites More sharing options...
ylstaffer Posted August 25, 2009 Author Report Share Posted August 25, 2009 if you have power at the one wire on the compressor and the clutch is not working then you have a bad compressor I must not be articulating this clearly enough. There are two wires coming to the pressure switch by the firewall and NEITHER wire has power, which of course makes jumping them ineffective. My question is... shouldn't one of these wires have electrical current to it if they are in proper order? It makes no sense to jump 2 dead wires. Should I run a jumper from the battery to one of the wires and see what happens? Link to comment Share on other sites More sharing options...
mbsl98 Posted August 25, 2009 Report Share Posted August 25, 2009 You are correct that one of the wires to the firewall switch (pressostat) should have power. That switch merely completes a connection so that the power goes on from there to the compressor, and breaks teh connection if teh freon pressure drops too low. Power comes to the pressostat from the AC relay, so head back to that to see if there is power at the relay. There are complete wiring diagrams for 850's in teh stickies, but I believe that there are a few differences between teh 850 and x70 ACC systems, so not a perfect match. Sstill should be a useful starting point to follow current flow for most of the system. Link to comment Share on other sites More sharing options...
ylstaffer Posted August 26, 2009 Author Report Share Posted August 26, 2009 You are correct that one of the wires to the firewall switch (pressostat) should have power. That switch merely completes a connection so that the power goes on from there to the compressor, and breaks teh connection if teh freon pressure drops too low. Power comes to the pressostat from the AC relay, so head back to that to see if there is power at the relay. There are complete wiring diagrams for 850's in teh stickies, but I believe that there are a few differences between teh 850 and x70 ACC systems, so not a perfect match. Sstill should be a useful starting point to follow current flow for most of the system. Where exactly is the AC relay located and what does it look like? Link to comment Share on other sites More sharing options...
OniFactor Posted August 26, 2009 Report Share Posted August 26, 2009 haha, oddly enough, my 850 is having a similar issue. i believe the relay's located under the plastic cover that surrounds the fuse block, but i haven't had a chance to check, yet. i also am not sure which one it would be, under there, since i guess that's where all the relays are stuffed? anyways, who would've thought 2 cars so geographically close would have a similar problem... (i'm in Binghamton, NY) Link to comment Share on other sites More sharing options...
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