volvo 850 turbo ecc rec and ac lights not turning on

dave5570 · Post by **dave5570** » 18 Nov 2016, 16:32

Hello,
about two months ago, the blower made a grinding noise then stopped working. i bought and ordered a replacement, installed it, and still nothing. a the same time, the rec and ac lights didnt turn back on after i installed it. i thought it might be the resistor, so i ordered another. i installed it last night and still no rec and ac lights, and moving the slider doesnt accomplish anything. the green backlight on the ecc still works. so i'm thinking either the ecc is dead, or its the wiring harness. i've tried looking around on the interwebs, however i have not found any mention of the rec and ac lights not turning on, just of them flashing codes. any help would be appreciated.
thank you

Post by **Ozark Lee** » 18 Nov 2016, 19:24

Have you checked both fuses? There is one fuse for the controller itself and another for the blower.

Since you have a '96 the DTC codes don't work unless you build a special code reader but my guess is that trying to read the codes won't get you anywhere since it sounds like it isn't getting power to the controller.

...Lee

Post by **jreed** » 19 Nov 2016, 05:59

After checking the fuses, it might be a good idea to open up the case on the ECC and inspect the components and circuit boards inside for obvious signs of damage as found in this case from a few years back:
viewtopic.php?t=58028

dave5570 · Post by **dave5570** » 19 Nov 2016, 10:13

thank you for the replies,
i forgot to mention the fuses are good, the ecc is clean except for this line on one of the chips

: ecc.jpg (152.88 KiB) Viewed 2227 times

i'm also pretty sure i didnt miss any plugs, though its not impossible i did
wiring:

: wireing1.jpg (116.22 KiB) Viewed 2227 times

: wireing2.jpg (107.89 KiB) Viewed 2227 times

: wireing3.jpg (91.2 KiB) Viewed 2227 times

: wireing4.jpg (108.52 KiB) Viewed 2227 times

its very clearly been worked on before, as the resistor was a replacement, and the wiring looks kind of rough
could it be possible that the relay is bad? (the one near the resistor?)
any help appreciated, thank you.

Post by **Ozark Lee** » 19 Nov 2016, 16:32

The wiring visually looks fine as does the ECC itself. When the capacitors short out inside the controller it is obvious. You can test the fan itself by grounding the blue wire at the blower resistor. If the fan runs then that verifies that the fan is getting power and that the fan itself is operational. Beyond that I think I would start at the power connector on the back of the ECC to verify that the power is getting there. If it is the next step is to build a reader to try to get flash codes. Schematically the controller is a black box and there isn't much you can do to troubleshoot the controller itself other than "replace with known good". A junk yard controller isn't exactly "known good" but they typically are if they come out of a true wreck with lots of body damage.

The relay is the air conditioner compressor relay so it really doesn't come into play with your symptoms.

...Lee

dave5570 · Post by **dave5570** » 20 Nov 2016, 11:38

i'm thinking this:https://www.matthewsvolvosite.com/forums ... hp?t=34698 will be my cheapest/ best option at the moment. the system has stopped at the defrost/max heat option (best for my preference). now i notice when i plug the red/black plug (next to the blower plug) into the blower, it runs the blower. is it safe to do that? or must i run the switch off the blue wire on the resistor?

dave5570 · Post by **dave5570** » 20 Nov 2016, 11:41

i'm just planning to put a switch, and not worrying about blower speed at all. fyi

Post by **Ozark Lee** » 21 Nov 2016, 00:21

The red wire is always hot and, when working properly, the blue wired is pulse width modulated by a MOSFET in the "blower resistor" to vary blower speed. Max speed is a direct short to ground. The blower motor draws a fair amount of current so you want a fairly beefy switch and at least 18 gauge wire going to a ground, I would run 16 gauge myself.

...Lee

dave5570 · Post by **dave5570** » 21 Nov 2016, 16:01

ok, i'm looking at a 50amp toggle and i will probably be running it off the blue wire on the resistor just because.

thank you for your help.

Jsadler · Post by **Jsadler** » 04 Dec 2024, 22:18

I’m having the same problem. I took the relay out and replaced with new and didn’t fix the problem. Also took the resistor out or what the thing is next to the relay and it didn’t seem burnt. Problem arose when the car was jumped and the terminals were hooked up backwards. I replaced the ecc unit and all the lights light up except the REC and AC lights.