SwedeSpeed - Volvo Performance Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
32 Posts
Discussion Starter #1
Got the alternator upgraded, car is generally running well (for a beater car). The speedometer is iffy - it works sometimes (usually when the car is cold) and when it doesn't, it's dropping to 35-40 mph reading - I assume that's due to an incomplete circut in the speedo/dash, and one side of the circuit is pushing it to that point. Not a big deal, overall, at this point.

But i'm noticing an odd reaction. When the speedo is working, the engine seems to be perfectly fine (for a 20+ year old car). When the car warms up and the speedo fails, the engine feels like it's dragging. Almost how some older cars lose some hp when you turn on the AC unit. I guess the drag feel is constant when the speedo isn't working, but I don't really notice it (as it's the status quo at that time). On the commute this morning, the speedo flickered back and forth 3 or 4 times between work/nonwork, and I could definitely notice it.

Is this serious? Is this common? I'm not sure what is really happening here, so I'd appreciate some enlightenment.
 

·
Premium Member
Joined
·
19,952 Posts
Got the alternator upgraded, car is generally running well (for a beater car). The speedometer is iffy - it works sometimes (usually when the car is cold) and when it doesn't, it's dropping to 35-40 mph reading - I assume that's due to an incomplete circut in the speedo/dash, and one side of the circuit is pushing it to that point. Not a big deal, overall, at this point.

But i'm noticing an odd reaction. When the speedo is working, the engine seems to be perfectly fine (for a 20+ year old car). When the car warms up and the speedo fails, the engine feels like it's dragging. Almost how some older cars lose some hp when you turn on the AC unit. I guess the drag feel is constant when the speedo isn't working, but I don't really notice it (as it's the status quo at that time). On the commute this morning, the speedo flickered back and forth 3 or 4 times between work/nonwork, and I could definitely notice it.

Is this serious? Is this common? I'm not sure what is really happening here, so I'd appreciate some enlightenment.
I am assuming this is the '89 240 DL.

It seems as if the alternator is pulling big hp from the car when charging the battery. It also appears that the charging cycle has circuit problems affecting other electrics on the car.

Be sure the alternator is wired correctly and the alternator regulator is functioning per design.

George Dill
 

·
Registered
Joined
·
2,885 Posts
You may also have some other age related issues with the charging system.
Double check the alternator, do a voltage drop check, have the battery tested
and take a good hard look at all the cables and connections involved.
Don't forget the grounds.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #4
New battery, new alternator. Brand new - both are less than 3 months old.

I hadn't considered that it was a charging cycle issue - I was thinking that as it warmed up, resistance increased somewhere and there was some kind of feedback that effected... I don't know what. I'm sure the alt is connected correctly, which leaves me with probably a bad connection/bad wire somewhere between the alt and the battery, right? I think I'll go spelunking in the engine compartment this weekend....
 

·
Registered
Joined
·
3,126 Posts
I have a speedo diagnosis and from Cleanflametrap (Art) somewhere. When I find the link I'll post it here.
 

·
Registered
Joined
·
3,126 Posts

·
Registered
Joined
·
32 Posts
Discussion Starter #7 (Edited)
Thanks, John - I had seen that somewhere before, and I'll probably try that in the next few days (I discovered yesterday that I actually have a couple of unused AC adaptors laying around for no apparent reason). With the feel of the HP drop, though, I'm thinking that it's probably not a speedo issue - UNLESS (someone check me here) there's some kind of tie in with the overdrive? Could the lack of consistent signal from the speedo impede the OD from working? I only really notice the HP drop at highway speed - doesn't mean it's not there during local driving, of course.

This mornings drive makes me rethink this issue. Hit a bump or two on the road, and that caused the speedo flicker (and HP drop). It's got to be a weak connection somewhere (or a bad wire). Didn't get a chance to dig into it over the weekend, but it's going to be nice today, so maybe I'll get some time to look at it.
 

·
Premium Member
Joined
·
19,952 Posts
Thanks, John - I had seen that somewhere before, and I'll probably try that in the next few days (I discovered yesterday that I actually have a couple of unused AC adaptors laying around for no apparent reason). With the feel of the HP drop, though, I'm thinking that it's probably not a speedo issue - UNLESS (someone check me here) there's some kind of tie in with the overdrive? Could the lack of consistent signal from the speedo impede the OD from working? I only really notice the HP drop at highway speed - doesn't mean it's not there during local driving, of course.

This mornings drive makes me rethink this issue. Hit a bump or two on the road, and that caused the speedo flicker (and HP drop). It's got to be a weak connection somewhere (or a bad wire). Didn't get a chance to dig into it over the weekend, but it's going to be nice today, so maybe I'll get some time to look at it.
Could be a bare wire in the engine harness bouncing up against metal causing an intermittent drain on the alternator.

OTOH, could the hp drop be associated with the flaky OD?

Have you tested the speedo sensor in the diff? The wiring for this sensor is a known troublespot.

George Dill
 

·
Registered
Joined
·
3,126 Posts
IIRC I think that Art's speedo diagnostic includes checking the sensor on the diff first. As for the OD, my '88 244 automatic speedo is acting up (and no, I haven't had time to check it yet) and it doesn't affect the OD.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #11
Yes, check that wiring to the diff. By the way the FI computter uses a speed signal from the spedo.
FI? Trying to make sense of that, and coming up blank.
 

·
Premium Member
Joined
·
19,952 Posts
Yes, check that wiring to the diff. By the way the FI computter uses a speed signal from the spedo.
FI? Trying to make sense of that, and coming up blank.
The speedo sensor in the diff has a wire going (eventually) to the electrics that control the speedometer and these controlling signals are used by the ECU to set fuel parameters.

Seems to me this also affects the OD operation, cruise control and ___?

A "computter" is the malady currently affecting Tiger Woods.

George Dill
l
 

·
Registered
Joined
·
32 Posts
Discussion Starter #14
The speedo sensor in the diff has a wire going (eventually) to the electrics that control the speedometer and these controlling signals are used by the ECU to set fuel parameters.

Seems to me this also affects the OD operation, cruise control and ___?

A "computter" is the malady currently affecting Tiger Woods.

George Dill
l
Gotcha. If it affects the fuel parameters, could that be the issue with the hp drop? It's a beautiful day to crawl under the car...
 

·
Registered
Joined
·
172 Posts
On my 1990, the dash would go dead once and a while- speedo and other gauges would stop working, and the overdrive orange light would light up (like you had selected overdrive bypass). What I did not know was when this occurred the alternator was not charging and the car was running off the battery. The event got to the point that the car died on the highway.

The problem was a faulty circuit board for the dash. I found a used one, installed it and the problem has never returned.
 

·
Registered
Joined
·
3,126 Posts
Check the exciter wire that goes from the alternator to the firewall harness for condition and good connections. IIRC the wire is red and it's thin, not a cable.
 
1 - 17 of 17 Posts
Top