Yet another Volvo EDC problem - a duff potentiometer?

[scubaman]

I’ve searched the forum for the EDC related issues but didn’t find one that exactly matches the glitch that mine developed recently. My engines are TAMD75P’s.

This happened once during our delivery with MapisM and then again a few times over the last weekend.

In all occasions we have been cruising at 8 knots (around 900 rpm), when the revs on the port engine suddenly drop to tickover (600 rpm) and the engine then refuses to rev up. When I put the levers on neutral, the port engine goes into reverse. Once I press the ’N’ button on the EDC panel, the engine goes to neutral and everything seems normal. Stb engine behaves normally (ie. stays at 900 rpm, etc.). No error codes on the panel.

I did a test from the fly just after having this happen for a few times and didn’t have any problems so I’m inclined to think that the lower unit has the problem. I then checked the connections behind the lever unit but everything seemed normal. Also did the recalibration as per the instructions in the user manual. However, upon doing this I noticed that the port lever doesn’t make the metallic ‘click’ sound when I put it in forward/reverse.

Following morning we drove some 20 mins. at 8 knots and didn’t have any issues but I’m sceptic that the recalibration has cured the problem.

My layman’s logic suggests that there might be a mechanical problem might with the throttle, maybe the potentiometer???

Has this happened to anybody else? I read from Nick_H’s post the the potentiometer is a Bosch part and easily changeable, any pointers as to which part number/source to use for finding a replacement?

Any help and comments will be greatly appreciated!

 

[jimmy_the_builder]

I had some intermittent throttle probs, and I thought at first it might be the pots .... but in the end I found that cleaning the contacts between the throttle assembly and the loom completely solved the problem.

 

[MapisM]

When I put the levers on neutral, the port engine goes into reverse.

This is imho the weirdest bit, particularly since you're telling us that this misbehaviour happened again in the same way.
And just to further complicate things, when it happened during our cruise, IIRC you noticed that the f/b levers were not in neutral.
Which in theory should not affect the behaviour of lower throttles, but it was a funny coincidence anyway.
I'd be curious to hear from Volvopaul if he ever experienced anything similar.

 

[James L]

I had a similar problem with my older electronic controls, turns out some water had gotten into the bottom of the control box, not enough to be splashing on anything, but it caused condensation on the electronics and this caused weird intermittent problems like that. Depended on temperature etc.
Also even though both sets of controls led to the same box, I only had problems with the downstairs control. The box was at a slight angle and there was more condensation where the lower controls connected.

Led to a very confusing anchoring experience, when trying to drop the hook just after dark on a wet and windy evening - one engine was in reverse when the lever was in neutral. Couldn't figure out why the wind was blowing the boat in such a weird way...

 

[scubaman]

Thank you for the comments! Looks like before replacing the pots, it's more searching and wd40.

James L, when you say 'control box', I take it that it's within the throttle unit or is there one somewhere between the throttles and the engine?

 

[James L]

On my controls, the throttles are connected to a control box for each engine, these then control actuators that move the mechanical cables for the gear and throttle.

like these

http://controlmastersinc.com/zf_microcommander.htm

I would guess the effects of water ingress into your units could have a similar effect. Not sure how easy that is to check though.

Good luck.

 

[volvopaul]

I’ve searched the forum for the EDC related issues but didn’t find one that exactly matches the glitch that mine developed recently. My engines are TAMD75P’s.

This happened once during our delivery with MapisM and then again a few times over the last weekend.

In all occasions we have been cruising at 8 knots (around 900 rpm), when the revs on the port engine suddenly drop to tickover (600 rpm) and the engine then refuses to rev up. When I put the levers on neutral, the port engine goes into reverse. Once I press the ’N’ button on the EDC panel, the engine goes to neutral and everything seems normal. Stb engine behaves normally (ie. stays at 900 rpm, etc.). No error codes on the panel.

I did a test from the fly just after having this happen for a few times and didn’t have any problems so I’m inclined to think that the lower unit has the problem. I then checked the connections behind the lever unit but everything seemed normal. Also did the recalibration as per the instructions in the user manual. However, upon doing this I noticed that the port lever doesn’t make the metallic ‘click’ sound when I put it in forward/reverse.

Following morning we drove some 20 mins. at 8 knots and didn’t have any issues but I’m sceptic that the recalibration has cured the problem.

My layman’s logic suggests that there might be a mechanical problem might with the throttle, maybe the potentiometer???

Has this happened to anybody else? I read from Nick_H’s post the the potentiometer is a Bosch part and easily changeable, any pointers as to which part number/source to use for finding a replacement?

Any help and comments will be greatly appreciated!

Hi Kivi, you need to check both 8 pin plugs on the wiring loom, also inside the black box at all the relays, pull them out and check for green corrosion. Check the big round plug that goes into the injection pump.

The reason it throttles back is the edc computer is sensing there is a disconnection somewhere that will affect the overall " drive" of that engine so it throttles back, it may do this if you were on the plane , but will also do it al slow speed.

This happened to me a few weeks back on mine, it just seemed like fuel starvation as it just throttled back on its own to idle but stayed in gear. I went to lower helm, switched off then back on again, it cleared and all has been good since.
I plugged I. Diagnostic key which showed a short or open circuit in the gearbox solenoid. In other words a break in the connection somewhere in the loom to the gearbox solenoid.
Have a good look around , pull some plugs apart you may find the problem.

 

[scubaman]

Thank you for the pointers Paul, sounds like there is quite a few places to check. I'll investigate further.

 

[crewejd]

I’ve searched the forum for the EDC related issues but didn’t find one that exactly matches the glitch that mine developed recently. My engines are TAMD75P’s.

This happened once during our delivery with MapisM and then again a few times over the last weekend.

In all occasions we have been cruising at 8 knots (around 900 rpm), when the revs on the port engine suddenly drop to tickover (600 rpm) and the engine then refuses to rev up. When I put the levers on neutral, the port engine goes into reverse. Once I press the ’N’ button on the EDC panel, the engine goes to neutral and everything seems normal. Stb engine behaves normally (ie. stays at 900 rpm, etc.). No error codes on the panel.

I did a test from the fly just after having this happen for a few times and didn’t have any problems so I’m inclined to think that the lower unit has the problem. I then checked the connections behind the lever unit but everything seemed normal. Also did the recalibration as per the instructions in the user manual. However, upon doing this I noticed that the port lever doesn’t make the metallic ‘click’ sound when I put it in forward/reverse.

Following morning we drove some 20 mins. at 8 knots and didn’t have any issues but I’m sceptic that the recalibration has cured the problem.

My layman’s logic suggests that there might be a mechanical problem might with the throttle, maybe the potentiometer???

Has this happened to anybody else? I read from Nick_H’s post the the potentiometer is a Bosch part and easily changeable, any pointers as to which part number/source to use for finding a replacement?

Any help and comments will be greatly appreciated!

If anyone is interested in this, I took my throttle pair apart and found this part -

Bosch 0280122001 Throttle-Valve Switch​

It seems like this is available on a certain jungle/river based web site. You may also find them on the bay of ee's.