Amazon: overdrive drops out when cold

[Othen]

Originally Posted by gjr0

"The solenoid is covered in the Volvo Green Book at Part 4 (43a) Overdrive in pp 4-2 and 4-3."
In my manual page 4-2 is a list of tools and 4-3 has a couple paragraphs about how the solenoid operates but nothing on testing.

Hopefully it is not the pump...

'That's all folks' - but it is just a solenoid: I think there is an assumption by Mr Volvo that a mechanic would know how to test a solenoid.

I think I said somewhere above that it would be a good idea to check that it is receiving power from the dashboard and inhibitor switches and that it has continuity through it to earth. Those are both easy tests and may be conducted without disassembly. If it fails either of those tests then the fault is definitely identified. These will not be definitive tests if the fault you describe is intermittent.

Someone made the point above about this being an intermittent fault, which is always the most difficult type of issue to diagnose. That is a good point, but if there is indeed a causal connection between the fault condition and temperature it should show up as winter approaches. If the fault becomes persistent as ambient temperatures cool that will support your thesis that there is a correlation and also make it easier to identify the issue.

When diagnosing issues I always start by doing the simplest and cheapest tests first - in the case of the overdrive that is checking the two switches and solenoid for power and continuity; everything else will require a degree of replacement or disassembly. It is up to you whether you do that or start by looking for a more involved cause for the fault - either way I wish you good fortune.

Alan

[Derek UK]

The very basic tests are visual and aural. Engine off, ignition on. Put into 4th/top gear. Put OD switch to on. You should hear the solenoid engage or be activated with a small clunk. Quiet surroundings may be needed. OD light should come on. Note the OD light will come on even if the solenoid doesn't work as it is just the circuit to the OD switch. If no clunk Solenoid isn't getting any power. This may be a failed or intermittant connection at the solenoid or at the OD relay in the engine bay. Corrosion on OD relay connections not uncommon.
OD wiring

[Othen]

Originally Posted by Derek UK

The very basic tests are visual and aural. Engine off, ignition on. Put into 4th/top gear. Put OD switch to on. You should hear the solenoid engage or be activated with a small clunk. Quiet surroundings may be needed. OD light should come on. Note the OD light will come on even if the solenoid doesn't work as it is just the circuit to the OD switch. If no clunk Solenoid isn't getting any power. This may be a failed or intermittant connection at the solenoid or at the OD relay in the engine bay. Corrosion on OD relay connections not uncommon.
OD wiring

What the OP could do to investigate this intermittent fault is run a temporary wire from the solenoid into the cabin to a telltale lamp (and thus on to chassis earth). The telltale would show whether the solenoid is being powered or not whilst driving: if the light goes out when the overdrive drops out then it will be obvious the wiring (or the internal coil of the solenoid) is at fault, if it remains lit then the fault must be elsewhere with the mechanical or hydraulic systems. Such an experimental rig would only take a few minutes and cost almost nothing to set up.

This is probably what I would do… but it is entirely up to the OP of course.

Alan

[gjr0]

That was helpful.

I was thinking there would be a spec for the resistance of the solenoid windings, like a 6V ignition coil is 2.7 ohms across the primary windings. The troubleshooting chart expects a 2A draw when 12V is applied to the solenoid. V= I X R says the resistance should be about 2 ohms.

Testing the simple stuff first makes the most sense. However, once the simple causes are eliminated it is nice to know what's next. The pick up screen has never been cleaned since I owned the car. I guess I missed that when I was catching up on the maintenance. It probably won't hurt to have a look at that.

There must be two types of pick up filters. My service manual shows a big one under a cover and the link from 142Guy shows a small one under a cover and behind a plug. The more rectangular plate looks familiar, I suspect I have the small type. Any good workarounds for pin spanner 2836 ?

[Othen]

Originally Posted by gjr0

That was helpful.

I was thinking there would be a spec for the resistance of the solenoid windings, like a 6V ignition coil is 2.7 ohms across the primary windings. The troubleshooting chart expects a 2A draw when 12V is applied to the solenoid. V= I X R says the resistance should be about 2 ohms.

Testing the simple stuff first makes the most sense. However, once the simple causes are eliminated it is nice to know what's next. The pick up screen has never been cleaned since I owned the car. I guess I missed that when I was catching up on the maintenance. It probably won't hurt to have a look at that.

There must be two types of pick up filters. My service manual shows a big one under a cover and the link from 142Guy shows a small one under a cover and behind a plug. The more rectangular plate looks familiar, I suspect I have the small type. Any good workarounds for pin spanner 2836 ?

Here in England we would say that 12/2=6Ω, but no matter - perhaps like our languages, mathematics is a little bit different here .

I'm pulling your leg of course. I think you are worrying a bit too much here; as long as the resistance to earth is in the low Ω range the solenoid should operate. Remember this is an electrical system designed 80 years ago, it would be unreasonable to expect it to operate within modern tolerances. As someone said above, the best test is probably to listen for the click when the solenoid engages.

Good fortune,

Alan

[142 Guy]

Originally Posted by gjr0

That was helpful.

There must be two types of pick up filters. My service manual shows a big one under a cover and the link from 142Guy shows a small one under a cover and behind a plug. The more rectangular plate looks familiar, I suspect I have the small type. Any good workarounds for pin spanner 2836 ?

On the J OD on my 1971 142, there are two filters. The pre filter (lump screen) which is rectangular and just pulls out of the hole in which it is installed. Then there is a proper cylindrical mesh filter behind one of those round plugs which requires a pin wrench to access. I have attached photos from the service manual showing both filters. Both filters are cleanable; however, new parts are available if you don't want to go to the effort (you should be ordering a replacement cover gasket). On the J OD there is a magnetic strip glued to the inside of the cover. Make sure to wipe that because it accumulates metallic 'dust'.

Absent a pin wrench, if you have a sacrificial needle nose pliers of the correct size they will sometimes work depending on how tight the plug is; but, that definitely qualifies as a bodge. This enterprising individual makes a very nice home made pin wrench

https://www.youtube.com/watch?v=AFz5SlLC1JE

However, pin wrenches are $12 so why bother (as long as the pin size is correct)

https://www.amazon.ca/CCTVMTST-Adjus...04467197&psc=1

Before fiddling, you should confirm what type your OD unit is because the design did change. Based upon the 140 Volvo service manuals the later J was on the B20B. The earlier P OD came from the B18 cars. The J OD has the cover plate on the bottom and I think the P OD has the cover plate on the side of the OD.

[gjr0]

Partial result ?

It does appear to be a later overdrive unit. The click from the switch is louder than the solenoid engaging. I had to get under the car and unplug and reconnect the wire to hear it.

The resistance measured between the terminals was 5.5 ohms. (and BTW 12/2=6 not 2 even here.) From the power side to the transmission case was 5.6 ohms and no matter what scale there was nothing between the terminals and the body of the solenoid.

I drained the old fluid, cleaned the magnet on the cover and the rectangular screen. Refilled it with 15W-40. I did not remove the plug for the fines filter. I tried tapping a 3/16" rod that I stuck in one of the holes but it didn't budge.

I'll see what the local parts stores can come up with for a pin spanner. The Volvo part seems to be unobtainium now or at least nobody is paying enough to bring theirs to the top of search results.

It was 35°F this morning and after one hiccup, it worked fine. Tomorrow is supposed to be the same low temp. I'll see what happens.

[Derek UK]

If it is indeed a J type OD the solenoid is on the opposite side to the D OD. It's a much more complicated solenoid and does work with oil pressure. The O rings in it go bad and let oil past them. This can cause hydraulic lock and that will cause problems. They can be rebuilt. New ones are expensive. £120-130.
I would expect Mike Dudek at iRoll to have them in the USA.

Look through here for info and pictures.
https://forum.tssc.org.uk/topic/6540...type-solenoid/

[Othen]

Originally Posted by gjr0

Partial result ?

It does appear to be a later overdrive unit. The click from the switch is louder than the solenoid engaging. I had to get under the car and unplug and reconnect the wire to hear it.

The resistance measured between the terminals was 5.5 ohms. (and BTW 12/2=6 not 2 even here.) From the power side to the transmission case was 5.6 ohms and no matter what scale there was nothing between the terminals and the body of the solenoid.

I drained the old fluid, cleaned the magnet on the cover and the rectangular screen. Refilled it with 15W-40. I did not remove the plug for the fines filter. I tried tapping a 3/16" rod that I stuck in one of the holes but it didn't budge.

I'll see what the local parts stores can come up with for a pin spanner. The Volvo part seems to be unobtainium now or at least nobody is paying enough to bring theirs to the top of search results.

It was 35°F this morning and after one hiccup, it worked fine. Tomorrow is supposed to be the same low temp. I'll see what happens.

That is some progress already - you have eliminated an electrical issue without taking anything apart.

Regarding the pin spanner: I noticed someone's comment above and remembered I'd lost the one for my angle grinder some years ago (and had been using some plumbers' grips), so I ordered this one from Amazon:

https://www.amazon.co.uk/dp/B095LCP7...roduct_details

... which was just £4.99 (about $6) delivered to my house. It is made in China of course, but I'm really impressed with the quality - and delighted with the price (sometimes it is hard to believe how cheap Chinese manufactured goods can be). I have no idea whether it would fit your requirements or not, but for the price it might be worth a try.

Good fortune,

Alan

Addendum: I have just noticed that you mention there are two terminals to the solenoid. In that case I think it must (by elimination) be a Type J rather than a Type D. I have the Type D unit on my 1963 122S (it started life in an early P1800 I think), and I recall the solenoid only has one electrical connection (the earth return is via the case) - and as yours isn't like that I think it must be the later type.



Just a thought - have you checked the inhibitor switch for good continuity (and wiggled the gear lever about a bit to make sure it remains sound if it moves about a bit)? That might cause the symptoms you are describing.

[gjr0]

Yesterday morning was the coldest so far (30°F) and the overdrive worked fine. I'm still going to get a pin spanner and clean the fine filter. I may even spring for a new gasket...

Thank you to everyone for your help and interesting and informative(!) links.
Greg